Genetic and Cytological Maps of the Autosomes in Drosophila pseudoobscura Citation Tan, Jiazhen (1936) Genetic and Cytological Maps of the Autosomes in Drosophila pseudoobscura. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/72KD-6D58. https://resolver.caltech.edu/CaltechETD:etd-06302004-101131 Abstract No Abstract. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: Biology ; Genetics Degree Grantor: California Institute of Technology Division: Biology Major Option: Biology Awards: Caltech Distinguished Alumni Award, 1983 Thesis Availability: Public (worldwide access) Research Advisor(s): Dobzhansky, Theodosius Grigorievich Group: Caltech Distinguished Alumni Award Thesis Committee: Unknown, Unknown Defense Date: 1 January 1936 Additional Information: Jiazhen Tan is listed as Chiah-Chen Tan in the 1936 Commencement program. Transliteration developments have changed the form of the name. Record Number: CaltechETD:etd-06302004-101131 Persistent URL: https://resolver.caltech.edu/CaltechETD:etd-06302004-101131 DOI: 10.7907/72KD-6D58 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 2784 Collection: CaltechTHESIS Deposited By: Imported from ETD-db Deposited On: 30 Jun 2004 Last Modified: 29 May 2024 18:13 Thesis Files Preview PDF - Final Version See Usage Policy. 6MB Repository Staff Only: item control page

GENETIC J1ND CYTOLOGICAL M.AP,S OF THE AUTOSOIIEI: IN DROSOPHIU\ PSF.UDOOK~CUBA Thes5_s by In P:::rti c: l Fulfillment of the Doetor of Philosopby CALIFORNIA INSTrrHTE OF' TECHNOLOGY 1956 To Professor Th.. Do'Jn~frrn,sky, under whor:W direction the :following 1;;o:r1:. \')8.$ a.one' t'.'.le m>.t~or d.esire3 to e:::press his deepest grr:d:,itude for his guidance and constructive criticisms. To Professor A. H• .Sturtevant, the nuthor de;3ires to express his most sincere appreciation for his encoure.gement and stimulcl.ting tAaching, his helpful :suggestions; anc1 his ind!h;3pensable advice. To Doctors C. B. Bridges, J. ,Schultz, 2.nd H. Bs.uer, the 2.uthor giv0s his sincere thanks for their suggestions on the improvement of the salivary chromosome technique. To Doctors F. A. E. Crew and P. C. Kollex· of Edinburgh University, 8cot1Flnc1, the author wishes to e:::presD his indebtedness for the use of some of their mutant stocks. A pc.rt of the work was done through the aid of a Rodkef eller Foundation grant to Professor A. H. Sturtevant. To both the Fo1.m- dation and Professor .Sturtevant, the author is deeply obliged • .Finally, the author exp:resses to all of the members of the staff of the Genetics labo:r.atory, California Institute of Technolog;,r, his appr0ciation fo1· the critic ism, suggestion, nnd assistance, which have been of continuous value during the prosecution of this work. i. TABLE OF CONTENTS THE PROBLEM 1 MATEHIJl,LS f\ND METHODS 2 GENETIC MAPS Introduction 7 Description 8.nd locG.lization of mutr:mts 9 TJ~,e second chromosome 9 B0re (Be.) 9 Smoky (Sm) 10 gl8.Sf' (gl) and it::~ inter8.ction v.rith orange (or) 10 bithorax (bi) 15 pink(p) o.nd it::: inter;.:1.ction with orcmge (or) 17 pauciseta.(psl) and its ellelomorph(ps2) 18 The third chromosome 21 orcinge (or) 21 purple (pr) 21 Scute (Sc) 21 crossveinless 22 Jagged (Ja) 24 abrupt (ab) 27 Bl2,de (Bl) 32 n8.rrow(na) and plexus (px) 34 The fourth cli..romosome 37 Curly (Cy) 37 jaunty (j} 38 incomplete (in) 58 multiple nllelomor1•fi,:; of tangled ( tg) 41 Rough 45 j_j_ Construction of genetic maps 46 SALIVARY GLAND CHROMOSOME MAPS Introduction 55 Origin of translocations 57 Genetic r'.nd cytological a.nalysis of transloca:t,ions 62 Translocations tha.t involve two chromosor,1es 62 Y- chromosome translocations 6 ') <~ Y-II A, B, C, D 63 Y-III A, B 68 Y-IV A, B, C, D, E 73 Reciprocal trPnslocations 79 II-III C 80 III-IV B, C 86 Non-reciprocc:.l translocations 93 II-III A, B 94 III-IV A 106 Translocations that involve more than two cbromosomes 110 Y-III-IV A, B 110 II-III-IV A 114 Y-II-III-IV A 115 Y-II-III-IV-V A 116 Interra.cial inversions in II and III chromosomes 117 Construction of cytological maps 119 DISCUSSION 120 sm.11.MARY 131 LITER/\.TURE CITED 134 , -..1--, THE PHOBI&..JJ! Drosophila pseudoobscura presents considerable interest as an object for the study of a number of genetic problems, especially those connected with hybrid sterility and methods of race and species formation. As shovrn by Lancefield (1929), this species contains two races, race A a11d race B, which produce, when crossed, sterile male and fertile female hybrids. The two races are indistinguishable exter- nally, but differ in a number of physiological characteristics (Shapiro . 1932, Poulson 1954, Dobzhansky 1935). I have shown in a previous work (Tan 1935a,b) that the gene arrangement in the chromosomes of the two races is somewha.t different, there being four inverted sections in the chromosomes of the hybrid. An analysis of the cause of the sterility of the hybrids in this case (Dobzhansky and Boche 1933, Dobzhansky 1933tj.,b, 1934a, 1936) has shovm that it is due to interaction of genetic factors rather than chromosome incompatibility between the two races. Lancefield (1929) and Koller (193~ found that the factors responsible for the sterility of hybrids are located in the X-chromosome. Dobzhansky has further demonstrated that some of these factors are also present in the autosomes. As a basis for these studies it is necessary to work out the genetic and the cytological maps of Drosophila pseudoobscura chromosomes. Especially, when the question of the distribution of the ster- ility factors in the chromosomes of the two races is raised, and their :celation to interracial distinction in the chromosome structure is to be settled, such information is essential. With the above aim in view, the present investigation is undertaken. -2- Drosophila pseudoobscura Frolowa is a species native in the Pacific Coe.st of North .America, which has for a. long time been car.fused with the European Drosophila obscura Fallen; its description 1-mder this name can be found in Sturtevant•s monograph of the genus Drosophila (Sturtevant 1921) • Frolowa and Astauroff (1929) have shown the two forms to be really distinct species, and have given the name pseudoobscura for our object. Lancefield (1929) observed that the species pseudoobscura consists of two races, called A and B, which produce sterile hybrids when crossed. Tan (1925) and Koller (1956) found the two races to be different in gene arrangement - they differ in four inversions in as many chromosomes. Moreover, strains of the same race consisting of four different geographic regions may also differ in gene arrengement, and so it becomes necessary for the purposes of this work to use always a definite standard strain. Race A strain from Georgeto~n, Texas, was chosen. The procedure adopted in breeding this species consists of keeping the flies to be crossed for three days in a vial, in which a small chip of food is placed, before transferring to a half pint culture bottle containing food. For linkage experiments all cultures were raised in an incubator at 2s 0 c, for it was shown by Plough (1917) in Drosophila melanogaster that the amount of crossing over varies with temperature, though such effect has not yet been reported in our species. The apparatus used, such as incubator, etherizer, culture bottles, and the formula of food, were essentially the same as described by Bridges (1952). The counts from a bottle were continued for 12 to 14 days after the first day of hatching but not until the appearance of the succeeding generation. -3- All mutant stocks of race .A Drosophila pseudoobscura kept in this laboratory were used for the purpose of constructing the genetic maps. Some of them were sent here from the Genetic Laboratory of Edinburgh University, Scotland, through the kindness of Doctor P. Koller, to whom the author wishes to express his indebtedness. In the course of the investigation a few new mutants were discovered by the author and some of them proved rather valuable because of their favorable loce.tions. Professor Sturtevant also kindly let me use some of the new mut- ruits he had found. In constructing genetic maps, the distance between two nea.rest genes was determined by the percentage of crossing over betvrnen them. In a few cases where a big gap lies between two adjacent genes, the determination based on direct crossover values might not be accure.te enough on account of double crossovers which have escaped detection. In order to establish the cytological maps, twenty_ two translocations involving different chromosomes (exclusive of X chromosome), were obtained with the aid of X-ray. Details regarding the origin of these tra.nslocations will be described later. For each trans- locati.on parallel genetic and cytological analysis was carried out. Genetic analysis of translocations consisted of testing for (1) viability and fertility of duplication and deficiency heterozygotes (2) viability of homozygous translocations, and (5) location of the breakage points. Translocations that give rise to viable hyperploid or hypoploid zygotes are more useful than those which do not; for in former cEJses tests for duplicating fragments usually give a more accurate information as to the whereabouts of the breakage loci than the crossing over tests do. Espec- ially since there were not enough numbers of known genes properly distributed -4- in the autosomes of the species, the determination of the breakage points by means of comparing the crossover values in a translocation and that in the control was rather limited in value. Individual salivary gland chromosomes can be identified in any nucleus, once one is acquain:ted with their distinctive characteristics. The correspondence between the respective chromosomes in the salivary gland cells and their counterparts among the linkage groups knovm in the species was previously established (Tan, 1935) by studying the inverted sections in the different chromosomes~ Since each strimd converging to the chromocenter represents the conjugated homo.Q.ogous chromosomes in structural homozygotes, and in case of heterozygotes (inverdon, tran.slocation, etc.) the section containing similar loci are paired, fordng the chromosomes to fora/sometimes very complex geometrical configurations, the breakage points of different chromosome aberrations were determined in the salivary gland cell of the hybrid larvae between standard strain and a particular translocation stock concerned. In cases of Y-translocations, only male hybrid larvae were heterozygous for translocatio:ns, B.nd iiherr-~fo1~e only male larvae were selected for cytological study. As to the rest, the work was done mostly in female hybrids, since male hybrids were decidedly inferior to female for that purpose. The aceto-carmine smear method for studying the salivary gland chromosomes has been applied as described by Painter (1934a,b). There are, however, a few points of improvements which ma.y be mentioned here. Larvae selected for salivary chromosome study should not only be old, about ready to pup<d:.e, but also they must be well fed. As -5- soon as a good many larvae hatched in culture bottles, parent flies were removed, !30 as to prevent them from laying too many eggs, which would eventually hatch out to share the food. When the larvae were partly grovm (about 7 days), about 1/8 cake of Fleishrmmn 1 ;3 yeast was put in on the surface of the food in each bottle. tles were then kept at low tempero.:ture, about iso larvae becaI!le big enough to dissect. The culture bot- is 0 c, unt:U the According to the advice of Drs. Bridges and Schultz, the dissection of the larvae and the fixation of the glands were made at a low temperature. For this purpose, a depression slide was supported by a paraffin mold on the two opposite edges of a rectangular copling jar, which could be filled with ice blocks. The thick slide.was about half immersed in the ice water. The staining solution and the normal saline were chilled too. The larvae were transferred from culture bottle to the hollow depression of the slide. Dissection was performed on the cooled smooth surface of the slide. Glands were transferred by the tip of a needle to a small syracuse dish containing chilled staining solution. After the glands were left there for about 15 to 20 minutes, they were mounted up, usually 2 or 3 pairs on one slide, ~mashed gently and sealed up with paraffinmastic. one. Third, how to convert a temporary moimt to a permanent Temporary mounts of salivary gland chromosomes could usually stay good for about a week. Drawings were made during that interval. In order to preserve desirable figures permanently, a simple technique was developed following the suggestion of Doctor Bridges to change temporary mounts into permanent ones. It consisted of scraping off the wax sealing by means of a knife and then dipping the slide with -6- the cover glass on into 95% alcohol. night. Allow them to stay there over The cover glass usually came off on the next day. If' they failed to do so, they could be easily teased off by putting two fingers at one edge of the cover to keep it from moving and using a fine forcep with the other hand to wedge the edge of the cover up. The tissue may adhere to the surface of either slide or cover glass or both. The detached slide and cover slip were then returned to 95% alcohol in separate vessels for 10 minutes before being mounted up with eupral. Not infrequently in the process of conversion from temporary to perman- ent mount, the smeared tissue might fall off from either the slide or cover, and get lost. Following the advice of Doctor H. B9uer, clean slides, on which tissues were going to be mounted, should first be smeared with a very thin film of 45% albumin solution and allowed to dry completely before u~d.ng. Vfuen glands were mounted on such slides, they· always got stuck on the surface of the slide, and hardly ever fell off in the process of changing to permanent mounts. All drawings with two exceptions were made nnder the objective 120 end ocular 10 Zeiss, with the aid of a camera lucida. The two exceptional ones, figures 26 and 27 were made at a even higher magnification, objective 90 and ocular 20, for demonstrating the precise nature of a non-reciprocal translocation. two kinds. The figures are of Figures showing the composite maps of the three autosomes were copied from Dobzhansk-y and Tan (1936). All others were original drawings made from individual preparations of hybrid larvae. Since it rarely happens that a chromosome is clear in all its parts, in most drawings the banding was represented only in the clear sections, the remaining sections being represented by dotted contour lines. As an aid for description, Dobzhansky and Tan (1936), following the example of Bridges (1935) in Drosophila melanogaster, subdivided the chromosomes of pseudoobscura into one hundred arbitrary sections, numbering them consecutively from the spindle fiber to the free end in each chromosome. The sarne numbering is adopted here. The breakage points of various translocations, which were determined by studying the homology of salivary chromosomes of heterozygous trans'j,.J.ocations, are indicated in those composite maps by lines above. Hence, the limits and nature of each translocation can easily be found at a glance simply by reading the sequence of the numbered section in the composite map. No attempt was made to detect the precise point of breakage in every translocation with respect to the faint bands. There were, however, a few cases, which, as will be point.ed out later, do clearly demonstrate the exact loci of breakage. GENETIC MAPS Introgugtio11 The phenomenon of linkage of genetic factors was discovered in sweet pea (La.thyrus odoratus) by Bateson al.id Punnet (1905', 1911) who named it "gametic correlation" and spoke about "coupling" and "repulsion" of genes. The term linkage and the idea that this phenomenon is due to the location of linked genes in the same chromosome were proposed by Morgan (19lla,b). Sturtevant (1913, 1915) , using the degree of linkage as a measure of the distance between the loci of the genes in a chromosome, has demonstrated that genes are -8- arranged in a linear series and has constructed the first genetic map of chromosomes (in Drosophila melanogaster). The evidence for the theory of the linear order of genes, as well as the theory of genetic map construction has been adequately discussed by Sturtevant (1915, 1919), Muller (1916), Morgan and Bridges (1919) and others, and need not be presented here. Althou~most work of mapping the chromosomes has been done in Drosophila melanogaster, genetic maps are known at present also for maize (Emerson, Beadle and Fraser 1955), for several other species of Drosophila, and for a number of other organisms (Lathyrus, Piswn, Phorbitis, Gallus, Mus, Lepus and others). The fundamental principles of linkage proved to be alike for all these forms, and are probably universally valid. One of the major requirements for producing an accurate genetic map is the possession of a large nwnber of mutant genes in the linkage group in question. In Drosophila pseudoobscura the first mutant was reported by Sturtevant (1921). mutants. Metz (1916) reported three Lancefield (1919, 1922) gave an account of a very extensive series of sex-linked mutations in the same species. According to Morgan, Sturtevant and Bridges (1925) four autosomal groups of genes were also reported by Lancefield with 4, 6, 1, and 2 recognized loci respectively. These, together with the sex....linked group, made the total nwnber of linkage g-roups 5, which equal to the haploid chromosome nwnber of the species. In spite of the fact that the autosomal link- age groups reported by Lancefield were imperfect, some of his mutants have been found to be the same as some of the ones described below. For this reason, .the numbering of II and III linkage groups still follow -9- the system of Lancefield. The nwnbering of the IV linkage group is justified on the basis of cytological evidence, which shows that he representative gene of this group is located in the rod-shaped chromosome and not in the chromosome now designated as the fifth, in which no gene is reported here. Whether Lancefield' s 4th and 5th linkage groups corresponds to mine remains to be seen, because no mutant gene so far discovered in the 4th linkage group is certainly identical with any gene of either 4th or 5th group of Lancefield. Descri;Q.t.ion and._ Loca:,i.ization of I!ut~nt GeI!§!.§. Since the present investigation is confined to the autosome s of Drosophila pseudoobscura, only the autosomal mutants will be described below. In each chromosome mutants will be presented in an order more or less according to the time of -their discovery. The Se..9.Q.~d_Chro~osome Bare (Ba) Bare is dominant and homozygous vvhen lethal. It was discovered by Professor A. !I. Sturtevant (D.I.S. No. 1, p.41) in race A. It is characterized by the shortening of the macrocheatae. It was first shovm by Doctor Shultz to be independent of all but the second chromosome of Lancefield. The character can be easily distinbruished from the normal, and the viability and productivity of the heterozygous flies are excellent. Recently, Professor Sturtevant and the author have noticed that flies in the Bare stock may occasionally breed~rue, showing that homozygous Bare flies may sometimes be viable. -10- Smol;z .~(£Ill)__ Smoky, another dominant gene in thiA chromosome, was found by Miss Beers (D.I.S. No. 1, p. 41) in race B. The mutant gene causes the thickening and branching of wing veins, especially the second longitudinal vein. The minimum expression is the formation of small delta-like structure at the distal end of the second longitudinal vein. It is invariably lethal when homozygous. The mutant has been easily trru1sferred from race B to race A standard strain. By crossing to Bare and backcrossing the F1 Bare Smoky flies to wild type, it was found that Smoky is linked with Bare and the two are situated quite far away from each other, for the crossing over frequency was found to be more than 40%. Since the region between Bare and Smoky is long enough for double crossing over to occur freely, and since a double crossover could not be detected in a two point cross, the region must be longer than 40 units. The determination of the distance has, therefore, to wait until mutations will be obtained at intermediate loci. A Bare Smoky stock was established for the tests and localization of new genes in this chromosome. glass_(&!.j__~q, its :b.Ilter§.._q,tion v.[i.th.~~J.g,.tl Glass was discovered by Crew and Lamy (1935) • a recessive. colorless rim. It is The eye is reduced in size and surrounded by a smooth The irregular shape of the eye facets in the central area and numerous hairs pointing in all directions give the eye an appearance of extreme roughness. Th~pigment in the central space appears to be greatly reduced in amolmt and leaves only a pinkish or reddish hue. The character can be easily recognized with naked eye. The viability and fertility are about as good in wild type. -11- Crew and Lamy (1955) reported that glass gave free recombination with purple and short4,representatives of the third and fourth linkage groups. With Stubble, a representative of second. autosome, glass was found linked and observed to give about 47% of recombination. Since at the time when glass was introduced into this laboratory, the relations between the linkage groups short4 and Stubby of Crew and Lamy and those of Bare-Smoky and Curly of this laboratory were not knovm, glass was immediately crossed to Bare-Smoh.-y (second chromosome) and Curly (fourth chromosome), the third chromosome being represented When F1 Curly by purple of Crew and Lamy needs not to be tested here. males were backcrossed to glass females, first counts of F2 flies gave 25 Curly, 17 wild, 9 glass and 3 Curly glass flies. This indicates that glass is not located in the fourth chromosome. The result of backcross of Bare-Smoky males to glass females, however, gave only two kinds of flies, 80 glass and 91 Bare-Smoh.-y. Hence, it may be cnncluded that glass must be located in the second chromosome. Since glass was found linked with Bare-Smoky, a full count of flies were made in a single culture of cross between Sm Ba~~ x gld'd' to find the approximate location of glass in relation to Bare and Smoky. The figure given in table 1 gave Table 1. . .&!-~~ x gl6'6' Sm Ba ·--srfil;,Te crossover:,s__ double c ~ o. ls_t._re.fil-?_n 2t;_<f.=-L~~on ·-·· __L_)~-~-_ Nature of the cross: gl Sm-Ba Sm-gl Ba Sm-Ba-gl + 90 164 52 157 27 56 Ba-gl Sm total 20 20 546 ·----·-·---~-~--------------~--~ ------ -12- crossing over values of 42.0% between Bare and Smoky, 18.9% between Bare and glass, and 46.5 between Smoky and glass. Since the smallest number of flies were represented by Bare-glass and Smoky classes, which must be double cross-overs, the sequence of the three genes in the chromosome must be Smoky-Bare-glass, Bare being nearer to glass than to Smoky. A stock of Smoky-Bare-glass was then established. As pointed out above, glass eyes are usually light reddish in color. However, in pure glass culture, occasionally some glass flies were found to be light gray in color. When such flies were mated to wild type, all F1 individuals were of wild type. Among 164 F flies, (Table 2) 43 were not glass but orange in eye color. 2 Table 2. Nature of the cross: wild orange Q -9.!..o o x · Q .2!. d'c:J' + + .,..,. + + ·------~--------------- Observed 164 43 54 Expected 48 48 141 glass (light gray) glass (light red) -----------.··===--··· 13 ----===== 16 Of 47 glass flies could be segregated into two classes, 54 light red and 13 light gray in approximately 5 to 1 ratio. The result can be explained on the assumption that glass with light gray color was due to the interaction of genes glass and orange. The appearance of glass orange flies in class stock might either be due to contamination or to a recurrent mutation of the locus orange in the original glass stock. Since the history of the stock was not very clear, it could not be ascertained which was the actual cause. That glass with light gray color is due to the interaction of the genes glass and orange was confirmed by the results of following + -21- orc::nge (or.) eye color mutant ( and later described recessive and can eye color, n:it b(:: <list tion 'Rith Yiabili colorB. othe::· eye of tb.e s in nor1nal. Purple, <:mother recessive eye color mutimt., was ( It In case of ma.Les, t.he to chestnut. colorless. fr cm color '?'hen i is combined in color. appears Fhite orange, it becor1es three difi'ere!1t B.llels of the locus, '\'1hose co:on1.t:i.on c ' be from each other ano+,her, VJl1en one of co :ibined with 1 and orPnge , ~' to 47. of most bristles forms of of over (I and do:'l1immt gene tbe i~ather from the of some or to and ( " Ls he tv' ee11 o=c~~.111ge f1.bout hs.lf its cJe<'.r cut lo~n Scute. Due to :Lts Scute has l:.o be lo ca- The conbined bu:Llt to Crossve:'..nless p. ,~l) ?S Crew and an (D I •• c •\J. }.,Jo• . ' absence of the pos- ter1or cr·oss1re in. be .;;.bsent or :Lncom- not muti:mt is ir:; about normal; so is its Its "riabili the of recol'.lbin°tion th s vrill be 10ter, Le Ollt Te.ble 12 :L~elations t!-1e Nature of the cross: Ts.ble 1:2. Ba-cv Ctl 2:5 18 the Cjr BE. 18 of £. cross cv-Cy ·1?tlld .:1.3 ?15 + x cvd'd'. The result shm-:s, c free both Bio.Ce and Curly, gr:>nes In the meantime indicate 46. with coimts of the in ts.ble 13 of recombinrition betv·een that -25- of tf1e cross: 54 1 result of the of in 39 31 46 /50 mean 12) s rather than of the two gene 1d th has been is nei t11er in t11e fourth ch~rcnnos-ome t::-1e second chromoso::ne. no:~ Since it J.3 en tmtosorrw.l c;ene, :l t may lie el ther s in the third O'' i21 the fifth to Curly in Scute Scute \Vere rn.ated 'Nere selected counts of this m2. 4 kinds of flir3S of recombination flir:;s ut random 2nd tl1e en.ti:c-e of Scute cro;;sve3.n:1_ess 1ess is linked in the g;r shor·n :Ln t<,ble 14, g1:ve 45. indicates that crossvein- of recombim;.tion bet :een Scute 1 of th<? cross: total 1 2 62 55 78 40 45 50 62 40 38 ()CJ :z 'Z -..:() 30 <Jq ?. ~ ,,. LL ·) ~'.5 100 75 111 70 74 84 ?,7 54 (,!<, .. 430 H _____.__,_ ~~25 655 that the locus of gave fcbout of rith Scnte, crossveinless must lie at one of the Before the tests could extrer::e ends of 9r .J)I'.. Q:I stock must be raised. time made the stock Bnother thi:cd chronosome do!ll.immt ;;ene, cross, orenge, out to 1:VEtS both and Jagged. also on the nevt muta'.lt, J[~ that r::fter the imd Jagged, f3S As the to , it seerJS more of the latter. Suffic,c: it here to was found located over at the hov:ever, end. ls a domirwnt mutation which we,s recently found by the &.uthor. extreme cases, the whole on all Three such in one of cultures bi Sn bithornx s becomes notched. onl;/ the inner margin of the may become , two an.cl be a.r" i:md one m.t:LLe, 4 of Teble 7) of t~1e cro~is Bo,re fems.le a s in December, l956. mEcted to y::Lld LHed to female obtained on sny , but both Bare crossed to 3 wil6 Each fact that the cross is shown in to.ble 15. Table 15. x + 0'6' Nature of the cross: .•..• _I_agged -----··-·(] £ fon-Ba Ba + Sm-Ba Srn Ba + Sm-Ba Sm 11 6 6 L;1 1 7 15 '7 25 ---·--.-.,----~.,---·-"- 4 16 •.i 10 Ba + ti 11 5 27 52 63 rmlf of the approxima , a..11.d. that vrHre is an D.ui~osomal that the d:i.stributed among the tvm sexes dorrrincJ1t. d' ·Ba + Sir-Ba Sm s that the Table lE ft1rther Since occurred in two non-cros classes, Bare group. was soon confirmed by seems not bi crosses between «is shmm in table 16. Table 16. Sm Nature of Uce cross: J~i <'f'6' x bi Bs. bi gl + -----------~~---·---- No. Sm-Ba-Ja bi-gl bi-gl-Ja Sm-Ba. 1 7 10 5 8 2 5 2 20 6 3 8 for of the flies To test for the Go lf;i.,ld were selected &nd flies 18 99 wild , and in F1 flies 'r:wre ~~he reaul t ca.n be -26- the n s shmrn in table 17, of 2:1 cross; Observed , v. hich indica 1 + ¥x 131 99 172.:J 59,7 153 77 on flies do not Indeed, v;hen even for severa.]_ true. ' is not been sl1o·vrr1 in. tt:tble 16, fliBS were then mated to g i:n -t/,(' rfi<? , re;_:iresentl3tives of. third In each case, fourth were selected in to or not Ja sb.or:: linked v;itb. the Cl"0~3S , the counts of the bs.ck- g1~ou.p; recessive to in e :Ln j ,, TrCJ_e 1~3. . '°. + 1 17 19 11 15 14 13 -27- l 68 icz. in hi ch iricJu6e on:~" t"'bich The ' 1- ' cf g;· then to , in 1:hich fore frolli the , Jc: cnn be lS or From thic; ' Sc than to or. , ;l:_ieh E:~ discovered vein. tl:e author. In , the vein n2y d the j i ol c c fl f I 4 r 1 r I I 'I i i; ...:s1- yield a total of 1512 flies, from which crossover vc:1.lne lietvreen _pJ' and Sc and that bet1neen Sc rn1d Dr are celcul2.tecl to be 2. 06% and 5 .12% :respectively. When these v;::i.lues are compared with the corresponding values, 22.8% and 24.7%, from the control (the counts of the ls.tter 1:n'e shovm in table 69), it is appa,rent that the frec~uency of crossing Table 69. · or Sc ·or. o~ x or ·or 6'6' -·-·-------·-----·~·-·-·-·----·-. ___ _±_.~_ ..:_:___ l'Jon-~y~ ~ single cro2so~~ J2_g_..1.__ _Reg.2 _ double c .o. 1,2 -~--.2L~ Sc.::J?.L.~OL-::§s.__,p£..._._,.QI.::£"::£ Sc -~tc:1].__ --~-9F-.:i.9~I'-r~~+45 75 19 17 17 over is greatly reduced in both regions. 23 5 206 Since the amount of reduction aI)peDrs to be proportl.onally gree.ter in the first region than in the second region, the break in the third ch..romosome probably lies to the ritht of the locus Scute. Having learned from above that crossing over in the whole third chromosome is consider1-1bly reduced by the presence of II-III C translocation, the author, using the gene orenge as the marker of the break in the third chromosome, made the cross of translocation females heterozygous for 2fil ..E 12§ in the second chromosome ~rnd or in the third chromosome to the Emltiple recessive msles. is shown in table 70. The result of the ma.ting A comparison of the calculated crossover values from this experiment, be:i.ng 46 .1% betv!een .Qm i:md 12.; 30% between_£ and or and 15. 9% betv.1een QI' and £.@_, and the corres1Jondine; values cDlculated from the data of the control as shoi!im in table 71 (41.1% betiNeen Sm 2nd l?... c',nd '37. 6% between p and ps, or being located in a separate chromosome assorts independently wlth any combination of second chTomosom.e genes) r-l cu ·+.) tjl 0 -82- r-1 0 -P r-1 0 C\l r-1 0 0 0-f x 010·:- ' o'~o P~ Hf Hf::-i 0 0 H'.O II HlP~ Hl 0 !S 0 E:-JIJ) .. 0 tCl) .--1 ,.Cl m E-1 <tjl 0 r-1 co r-1 co 0 L(,) -:.) ,. rl 0 ~ C) :z -83- Table 71. .2.r-13JlLlLJ~!~. !?!? x p ps 0101 ± - ·----··-·--·---·----~ ___§injQ__&_ _g~_y§l'§.____ double .9...!_2-.!__ Reg. 1 . _ _fi&R• 2 Reg. 1,2 Sm p ps __+__ J? 12§__ _ t?.fil.._ Sm P~-- -1?§_ __p_~ .§.m..J.JlL or + ru;: -±-·===.QJ'__ + ___!?-!- -±"=M- -!-_.~.::::-:2:I-..,,4°::-:: .. __9:f~. + or +__ _ total 1'Ton-crossg.Y.§1"s Cult. _]f..Q_, l 21 17 50 46 13 19 24 35 13 18 36 22 16 13 14- 15 372 2 11 10 18 20 8 10 13 23 9 5 12 11 8 2 2 8 170 32 27 68 66 21 29 37 58 22 25 48 33 24 15 16 23 542 shows that the region bet~11een· p and ps is somewhat reduced and the region between Sm a.nd p remains unaffected. The fact that or recombines with p in 30.2% and with ps in only 7 .9% indiccites that the break lies much closer to ps than to p Genetically between 12. and .£_§ lies an intermediate gene, gl. A cross II-III C ·-·~- ~~ x na gl 6'01 was made with the aim of deterna. Sm Ba gl mining the break of the translocation in relation to $J., narroi'i' being associe.ted with an inversion in the third cl:i...romosome is used as the marker for the third chromosome break. As calcula.ted from table 72., linkage values between Sm and ]3.a., betvTeen Ba and gl, and betv1een g1_ and .m1. are 4:4.2%, 30.2% and 7 .9% respectively. The normal frequency of crossing over (table 1) is 42. 0% betv1een Sm and Ba and 18. 9% between Ba and gl. It seems strange that in the region Ba-gl the experimental value is even higher than that in the control. Nevertheless, judged from .11§.:-gl crossover· value, it is obvious that the break must lie to the right of gl. Since the break in the second chromosome lies to the left of ps, it may be safely concluded then that the breakage point should lie somewhere betineen gl and ps, the two being 18 units arJart. Table 72. T II-III C -sm·-13~-;;:~~;_:;~¥¥ x gl nad'O' 01 -a -----·---------·- ·---~-"----- triple ..§..:b_nglr? crossovers --~·--·----~ ---·______double croi?_§Qyers ·-----·---- cross_overe_ _ __;l~·?..~.?;_ . reg. 1 reo·. 2 __!!?&__ 3 ~ --·-~--_ --~3~--- .. Non::-_crossovers cult. No. + Sm-Ba-gl-nn Sm Ba-gl-na Sm-Ba gl-na Sm-B0,-gl na Sm-gl-nci.. Ba Srn.-na Ba-gl Sm-Ba-na gl --------·· ---·----- -·-··-· ----· Sm-gl Ba-na tot2.l -~·-··--~·_ _ ...,. __ ,a 1 25 11 16 22 5 11 2 2 5 4 2 0,_ l l l 0 108 2 8' 7 8 7 3 2 0 2 0 l 0 0 0 0 0 0 38 3 9 6 7 15 19 5- l 1 2 LI. 0 l l 0 0 0 71 4 12 5 7 7 3 6 1 1 4 2 1 0 0 1 0 0 50 l 0 2.67 - - - ·-----------------------·52 --- 29 38 51 50 24 --··------- 4 6 ---~----~---.~ -----· ·--~-··- 11 11 5 ------ 3 2 2 -·-----.,..----------~~--- I (!) •t>. 'i -85- Test for viability of II-III C homozygous translocation was made by int~rcrossing tre.nsloccition ma.les and females heterozygous for Sm Qf Sc. If homozygous translocation individual were viable, the above mating should produce an appreciable number of wild type individua.ls~ The fa.ct tl'lat no sucl1 flies ar)pea.red in tb.e test cross indicates definitely that homozygous II-III C translocation individuals a.re not viable. Even if a few such flies do turn out as it would be shmm later in II-III A and B, they could very probably be flies resulting from double crossovers. The salivary chromosome configuration of heterozygous -Jrdt>S/ccafio111 II-III C is shown in fig. 21. Second chromosome is broken about the middle of section 59, and third chromosome is broken between sections 69 end 70. The short broken off piece from the second is attached to the basal part of the third, v1hich in exchange gives the excised long sect:l.on to the second. From the study of translocation Y-II C, ps is loc2.ted in sections 60 to 62. Since the frec;_uency of crossing over between the break and ps in II-III C is 15. 9%, the locus,.~' presuma.bly. lies very close to the terminal end of the second chromosome. The locus of EJ:, /-ii-ft apparently must lie to the ~ of section 59. As it has already been shovm in Y-III B transloce.tion, ri15k/tbe locus Scute lies to the ~ of section 72. The.break of II-III C, now loc2,.ted betvieen sections 69 and 70 therefore, lies a few sections r\5hfto the :EeFt. of Scute. This may a.lso account for the genetic result given a.bove that crossover frequency is more reduced in the region between_ or and Sc tban tbat bet11;een Sc and pr. -86- UJI-IV B' c Of three translocatfons that involve third and fourth chrornosomES, two are reciprocc>l. These are III-IV B and III-IV C. Heterozygous tr&nslocation males cBrrying the gene ora.nge in the nontreoted chromosome were mated to ..QT Cy: females. The result of counts in the two cases, as shovm in table 7'3, gives in each case even more 'rable 73. T III-IV .aa x or Cy ~~ or + --2;[_ or__g_;y·- or-:=======~==d' ~ .-~·-s__ ~--_J__~ III-IV B 46 46 41 50 32 31 27 42 ___ ____27 57 26 26 27 22 22 III-IV C 22 , ._... translocation flies than 'normals', indicating that heterozygous translocations are completely viable. and Judged from the results of crosses T III-+v ;?~ x or pr O'cJ' or Sc pr T III-IV oo x na in j 010, which are surrunarized in ta.bles 74, and 75 nA. in j .-..Table 74. T III-IV or Sc pr Table 75. >< or wr ~~ or Sc pr 559 III-IV B III-IV C 6'c3' 429 524 T III-IVecJ' x na in j ________:g.§l__Jn j + na in j 75 55 110 III-IV c ---------- 58 III-IV B ~n -87- respectively, heteroploid flies do not exist in either of the two trans- Genetic test for the break in the third chroniosome was attempted by making the mating T III-IV ~~ x or pr 6'6', the results of or Sc pr which are presented in table 76 for III-IV B and table 77 for III-IV C. T III-IV B ~~ x or pr cJ'Ci' ___qr Sc_..P.L_ ___, Table 76. . sin_gJ.§__9l'O§SQ.,:Yer:_?_.. Cult. No~ ____+_ double c .o. 1 ___fee g. g,_ _l,_2___ or-Sc-~·o_r__ or . Sq-:.1?£__: oE:::·§S__pL______§_g__-9£.:::·.}E____ tot. _I~g. 1 109 85 1 1 14 13 0 0 225 2 58 68 0 0 11 17 0 0 154 3 110 108 0 0 19 18 0 0 255 4 55 60 0 0 6 9 0 0 130 5 65 58 1 0 17 14 0 0 155 379 2 1 67 71 0 0 917 397 ·-----.r-.----·---·-. ·----·-----··---· Table 77. Cult. No. Non-c.ross~ + ~r-Sc-pr ------·---· III-IV c !i'!i' x or pr 0'6' or Sc :12r double CJJ. single c..rossovers Reg.2 122 Re~.l or -c-pr :Tc or-pr or-Sc pr T tot .. 1 65 46 0 0 15 14 0 0 140 2 95 104 0 1 24: 21 0 0 245 3 72 58 2 3 18 22 1 0 176 4 83 54 0 0 27 21 0 5 188 515 -----.----------· 262 2 ----·----~-~----·---- 4 84 78 1 5 749 The calculated crossover values in the two ce.ses as well as those in the control (cf. te.ble 69) are given in ta.ble 78. -88- Table 78. CompBTison of crossover w1lue in the third chromosome Reg.2, Sc/pr T III-IV B 0.3 15.5% T-III-IV C 1.33 22.2% Control 22.8 24.7% A compa.rison of these values shows a remarkable reduction in the frequency of crossovers in the region between Qr. and Sc in both III-IV B and III-IV C, indicating that tbe break in the third chromesome lies in this region in either case. rrhe fa.ct that linkage between Sc and J2!' is greater in III-IV B, 15 .1%, than in III-IV C, 22. 2%, suggests the possibility that thf) bre2.k is farther away from the gene Scute in the latter than in the former. Using IIB as a crossover reducer to mark the break in the third chromosome, ~ ~~ were mated in na in j na in J 6'6'. The results of separate crosses for the two translocations are SUJY1111arized in tables 79 Table 79. Cult• T IIJ-~V ~· ~!i? x na in j na in J 6'6' NQ! + na-in-j na in-j na-in j na-j in tot. 1 90 54 56 44 3 8 5 6 246 2 99 46 56 52 20 7 2 4 246 65 45 20 31 8 6 l 5 179 252 145 9/Z, 107 31 21 --- 8 15 67f> 5 -------- --~-------~--------·----·------· and 80 respectively. The data. from the control are shown in table 81. Frec;L.1ency of crossing over between in and j_ is 11.2% in III-IV B and 2.4% -89- T III:-J~Q ~~ X na in j rYd' Table 80. .n.a...J.lL..J Cult. ·No. Non-crossovers + na-in-,j -· === Crossovers j na-in tot. - ·- ·- l 93 56 5 5 155 2 100 89 l 0 190 193 145 4 3 345 Table 81. + -·---------·'*"' na in j Non-crossovers in _j_ + + na + na Cult. No. x na in jd'rY Crossovers . in + na + na tota.l l 75 47 60 47 16 9 11. 6 271 2 85 48 54 73 16 10 13 8 307 5 57 42 51 56 14 8 9 -·-·-..._.7 244 7'3 54 822 554 in III-IV C. Sil~ 541 _____ A comparison of these values with the value obtained from the control, 15.5%, shows that the break in the fourth chromosome is far avmy from the spindle attach..ment in III-IV B and near to it in III-IV C. · t s as a b eve, ---·-:-·-;T III-IV ~~ To repea...v th e seJne k"ind of experimen . na or in J were mated to na or in j d'd', and the results are shovm in tables 82 and 83 Table 82. Cult. No. Non-crossovers --·----·- + na-or-j-in .'LUI-:-IV B ~~ X na or j in d'd' na or .i in _ _$ingle _9rossovers double c .o. __fu3_g_._L_ Reg. 2 122 na-or J-in na.-or-in J tot. na-or-J in - 1 33 41 28 .25 6 6 6 5 148 2 69 68 32 21 5 15 11 6 227 102 109 60 44 11 21 17 11 375 ---- -90- T III-IV C 00 x na or j in 6'cl' na or j in + na-or-j-in in total Table 85. T Cult.No. l 155 100 0 255 2 54 60 1 115 209 160 1 5'(/0 for III-IV B and III-IV C respectively. in table 84. That in the control is shovm There appeared in III-IV B six crossovers between1lS: and 'I' able 84. lli!:.......Qr i:q._j_ ~~ X na or in j + No.n-=9_r.:2§SO_'\J""fl.'S _+____ 91 N. ". cl'6' Crossover::; in-L_________i}l_____ j _____ tot<?-1._ 89 16 11 207 Since this munbe1~ is negligibly smq.11, th€:3y were left out of con- sideration in the CHlcul13.tion of linkage vDlues. in and j_ are now found to give 6.0% crossing over in III-IV B, but the result as a whole ,seems consistent vri th that obtained from T II1.:;:IV _. B n x na in j d'd'. Concern- J ing the result of the mating III-IV __9_ - 'i?~ x na or in j d'O', in which no na or in j nc;, in orange and narrow crossover was obtained, there was only one fly representing the crOSf3over betweon in and~ That the crossing over in the regions between in, j_and the break is almost entirely suppressed indicates that the break in the fourth chromosome in III-IV C lies very close to the regions in and j, probably bet•rnen them. In addition to the above experiments, III-IV B and C were tested for the linkage of the genes ne2r to the free end. pU:C'l)OSe, T III-IV~ ~o were mated to na na. or tg5 Cy .,. or tg 0 cl'O'. For this The results, as -91- shovm in tables 85 and 86 for III-IV B and III-IV C re,specti vely, are 2 70 72 0 2 4 131 133 0 5 6 11 l 56 35 36 42 9 2 26 28 27 17 6 82 63 63 59 15 0 2 153 2 4 290 13 16 in perfect agreement with those from other tests. 8 3 202 0 0 107 8 3 309 Frec~uency of crossing over bet J1Jeen the break and tg3 is 43. 9% in III-IV C and only 3 .1% in 1 III-IV B, indicating that the break lies much closer to the locus tg 3 in III-IV B than in III-IV C. tg3 Moreover, the linkage values between and ~ are 9 .6 in III-IV B and 13 .6% in III-IV C, shmving more reduct:ton in the former than in the latter. The frequency of crossing over between !g_3 a:r1d .Qx is 17. 0%. in the control, as cal cul a tec1 from the data given in table 87. TA.ble 87. lliL9r ~X ~~ x na or to-3 ci'o., ------··-·-·----·-±------· ____::__~-Non-crossovers Cro5sovers ...!~".:Qy_ _.±___________~£___Qy__~-~·-tq:ta1-. --·----·------··-"" -----·-· . 96 94 17 22 229 ---· ~------~ ····----- ·-·---·---~----··--·--·- -92- Genetic tests for the viability of.homozygous III-IV translocations were ,also made. The plan of the test was essentially the same as der:3cribed for testing II-III translocations. for Qy- or Sc pr were mated to each other. T III-IV heterozygous In III-IV B, about 1/4 of the progeny was wild t;;rpe, which represm1ts the homozygous translocation individuals. These wild type individuals are normal in appearance. Some of such males were mated to na win j_females. The salivary gland chromosome figures of the hybrid larvae show attachment.of the third chromosome head to the base of the fourth, and of head of the fourth chromosome to the base of the third. Genetically, when the hybrid males were mated to .fill. or in _j_ females, only wild type and na m:: in _j_ individu-: als were obtained, as shovm in table 88, proving definitely that III-IV B Table 88. Culture }To. 1 2 T III-IV B r3'r3' x na or in j r3'd' na __oi:_:Ln ,j -·----na or in_j_ + 0___ 6' 2.. -· 6' - ... -..'"'.. -:t'... -·-··,.. 30 '56 30 35 _______ ..__. ~-··"" 8 10 15 homozygous translocation individuals are viable. ,,,.u...._.... 13 This has rendered it possible to keep III-IV B translocation in homozygous condition. But in the case III-IV C, no vrild type flies were obtained from the test cross, indicating that III-IV C homozygous translocation is not viable. The typical salivary gland chromosome configuration, shov-.ring a reciprocal translocation, is shovim in fig. 2.Z. for III-IV B. The third chromosome .is broken just below section 68, and the excised piece -93- is transferred to the broken end of the fourth, which lies between sections 94 and,95. The piece transferred from the fourth to the third includes 95 to the free end. The figu.re (fig. 2a) observed in III-IV C translocation, however, shows that breaks in both third and fourth chromosomes lie close to chromocenter. The third chromosome is broken in section 66, and the fourth in section 86. Comparisons of the cytological and the genetic data show a cons:i..stent agreement. That the break in the third chromosome is nearer to spindle attachment in III-IV C than in III-IV B ' exrilains well why the frequency of crossing over between Sc and .QE is higher in the former than in the latter. Similar correlation also holds for the breaks in the fourth chromosome. The fact that the fourth chro- mosome is broken in section 86 in III-IV C, almost completely suppressing the crossover between in and j_, gives strong support to the conclusion reached from the study of Y-IV translocation that the loci jaunty and incomplete lie to the right and left of section 86 respectively. That crossing over is considerably reduced between the break and tg0 in III-IV B, in which the break lies closer to free end, furnishes another evidence that ~ 3 and .QL are located in the opposite end of the chromosome from in and j_. Finally, as indicated by the hie;her frequency of crossing 7. over between the break and Qy: than between the break and tg 0 , the locus Q;y; lies to the right of tg3. In non-reciiJrocal 01,; "simple" translocations, a section of one chromosome (the donor) is attached to another chromosome (the recipient), but the section of the recipient is transferred onto the -94- donor. .Among twenty-two translocations, three translocations are app2.r- In two of them, designated II-III A and II-III B, ently simple ones. a section of third chromosome is excised, and intercalated into the In the third, III-IV A, a section excised from third second chromosome. chromosome has been intercalated into the fourth chromosome. The follow- ing is a description of the results of genetic and cytological analysis of these cases. Since III-III A and II-III B involve same tvm chromosomes, they are treated together. When II-III A. and II-III B translocation males heterozygous for ..Q!'. were mated to J2._ or feme.les, more wild type flies were produced than on:mee flies (table 89), indicating that the het9roz;y~gous transloWhen II-JJ.I males were p or cations are at least as viable as the 'normals 1 • Table 89. T II:::.b.II 6'6' x p or ¥!? --···-··----- - __()£.__ _________ .___ ~,,. +~·-----2£.__ __ __!?___a_ _!?___a_._ ---··-·-··-·----------..---·-------·-~··---·----· T-II-III A 118 114 84 73 II-III B 75 76 91 76 T me.ted to ..:e_ or females a few p and or flies were produced in each case, ( t.'.3.ble 90) , suggesting that the· duplications and deficiencies are viable. Table 90. T II-Ill au x p or ~!? - - - - - - - - - - p _?_r;__________~~ + p-or p or T II-III A 249 154 13 3 T II-III B 98 81 7 4 -95- The exact nature of the duplicating fragments was not r:1uite clear, until the result of four separate crosses of ll::J.11._ 6'<3- x o; pr ~~ for each or Sc pr translocation (table 91) gave ct considerable mm1ber of or and Sc 2!' individuals in each case. Sc .Qr flies are normal in appearance and Table 91. T II-III aa x or pr 5?~ - - - - - - _... ___o_~8,_C_J2_]'.'__ + or-Sc-ur or Sc-ur ------·------~"-----:--.----~- T II-III A 551 234 94 210 T II-III B 229 211 .164 187 appear in almost equal number as 'normals' (or Sc pr). In both cases, flies, having minute bristles and somewhat defective wings, are ab- Qr normal in appear a.rice, and the number of such flies was not as large as of Sc 12!' individuals. The above facts raise a strong presumption that Sc .m:- flies are duplications and Qr flies the deficienci1.:is. In both cases, apparently, the duplicating frabrment su~'Jpresses the expression of the gene, orange. II-III :;!~ x or pr o'a or Sc pr The result of reciprocal crosses, as swmnm~ized in tables 92 and 93, shows an unequal frequency of or and Table 92. Non-crossovers T II~III ~ ~~ x or pr aa or _;S_S'.__pr ------· Single cro,2~§..Q:~~X. LReg. 1 Reg. 2_ or Sc-pr _____or-~'?.:::==12-~ Cult. No. ---···--1 + or-Sc-Dr 79 56 53 65 37 26 18 13 345 2 45 22 11 42 15 9 15 2 159 3 64 25 28 27 22 17 15 4 202 4 97 34 37 69 25 24 15 3 504 - -~-- ----·------------------~--- 285 137 129 201 99 76 61 22 1010 ·----·~-----------·-···-----------------·--------·--- -96- T II-III B x or pr d'd' or Sc -or____ ~~ Single crQ.e_l?overs double -~· Reg. 2 Heg. 1 Cult. __lL-..L_ N~ ___-t__9y-Sc:...p:r____ or or-Sc -or Sc . ox·--or Sc-or tot. -~--------~---·-·· ,.,.... __._________ ..------------------------Te.ble 93. -----------·lSi.mJ..::_c-ro s s over.a ____ __ .._ ·-~----,--.·- ·-~--·-- -~-~ 1 LJS 30 21 41 18 17 9 4 183 2 36 29 14 35 25 15 14 4 168 3 45 37 58 34 25 15 9 11 210 4 34 45 24 27 13 16 10 7 176 5 52 33 36 42 27 7 16 11 224 6 53 35 25 41 21 12 7 3 197 209 158 218 125 82 65 40 1158 .261 b . . . . .,,-. . ."-'"'*----·-. .·-·-··-----------.., . _____ _Sc pr flies, the latter being almost twice as frec:iuent as the former. Moreover, if calculated on the basis of figures given in these tables, the crossover values in the first region, i.e. between QI:- and Sc, are 40.9% for II-III A and 41.5% for II-III B, and for the second region, i.e. between Sc and pr, 25 .5% for II-III A and 27 .(Jfo for II-III B respectively. These values, especially in the first region, when com- pared with the control data (cf. table 69), show a great :increase. ThiG phenomenon ma.y now be interpreted as due to the fact that there were a high munber of duplication and deficiency flies imvobred. Since these translocations are now definitely lmown to give viable duplications, and since under such circumstances the crossover values could hardly be trusted for test of the break :Ln the third chromosome, attention is now paid to find the extent of the duplicating frag1nents in the two cases by another method. first. For this reason, cytological analysis was taken up ;_97_ Investigations of salivary gland chromosomes reveal in both II-III A and II-III B the intercalat:ton of a short piece from third chromosome into the second chromosome. The deleted regions in the third chromosome are not the same in the two cases, but they overlap each other. But in the second chromosome, the locus at which inserted piece lies is different in II-III A and II-III B. Although the salivary glands were dissected from the larvae of the crosses between heterozygous translocation males and normal females, no good figures showing heterozygous translocat:Lons have ever been observed. obtained were of duplication flies. All the satisfactory figures Efforts were re 1Jeatedly made to obtg,in heterozygous translocations, but they were not successful. cause for that is unknovm. The It might be possible that duplication larvae are more vigorous than the translocation ones, though this has not been definitely proven. In any event, dv.plication figLU'eS showing the pairing of the inserted piece with its homologue have been observed, and they gc.ve the clue for establishing what part of the third chromosome is inserted into the second chromosome. Such pairing was, however, rare in II-III A, the reason for which will be made clear later. Figs. 3f and 2!1show where in the third chromosome a section is deleted and where it is inserted in the second chromosome in II-III A .viand II-III B respectively. In fig. ~ a buckle is formed in the middle region of the second chromosome. This buckle represents the intercalated piece, and it ce.n be homologized with the sections 64 and 65 of the third chromosome. Actual pairing of the parts have 'never been observed, -98- because of the fact that the transferred piece is small and inserted into a region ~n the second chromosome quite far away from the chrornocenter, n.ear which its homologue lies. Of a good many figures observed, fig. 24, tho-o.gh not showing actual pairing, is about the best that can be obtained. Fig. 25 shows the duplication of II-III B. Unlike II-III A, intercalation in the second cbromosome here occurs almost at the spindle attachment region. Partial pairing of the tr:msposed piece and its homologue has been frec::_uently observed. It is shovm in this figure that t:he two strands of the second chromosome fail to pa.ir in a part of its length, but pair very iiea:r· to the chromocenter. One of the two strands is attached to the chromocenter, one band after the paired region, and the other is continued with the extra piece which goes to the chromocenter region also. The inserted piece in II-III B, also including the characteristic section 65, seems to differ from II-III A by containing a part of section 66 instead of section 64. Figures 26 Md 27 show the second chromosome of a fly heterozygous for the duplication of II-III A at a higher magnification than other drawings. One strand of the second chromosome is broken, and the section of the third clrcomosome is intercalated. The parts of II above and below the breakage sometimes pair nearly completely with the inserted ¢lu11lication forming a characteristic buckle. The two figures shovr exa.ctly the same parts of the second chromosome and the same inserted piece, though they were obtained from glands of two different larvae, and. the chromosome in fig. 27 is much more distended. Sections No. 45 to 62 and 63 to 81 belong to the second and third chromosomes respectively. -99- Only sections 52 and 53 of the second chromosome are shown in these figures. The duplicating fragment of the third chromosome, which includes the sections 64 and 65 and small parts from the section 65 and 66, is intercalated in an inverted order into the section 52 of the second cbTomosome, bet1Neen the two light b<:mds "Q" and 11 R. 11 indicated by arrov1s. Band P is a charac- teristic very heavy one and is fou~d paired in both figures. Bands S are also paired in fig. 26 but not in fig. 27, in which, however, they stand out distinctly as two homologous bands in an l.ilpaired condition. ·Between the two heavy bands there lie the two lig11t ones 11 Q11 and "Rn. Q can be seen in fig. 27 almost paired and R., though not fol.md paired in either figure, could be clearly homologized in both cases. been seen paired in other figures. It has The two figures agree that the inser- tion point in the second chromosome is between Q and R,. and no vi,sible band in the second chrmllosome is lost. In other words, the second chromo- some has received a section from the third chromosome but has not lost even a single light bru1d in exchange. This evidence apparently fulfills the condition necessary for a demonstration of a simple translocation. The bearing of this finding on the problem of existence and origin of simple translocations will be discussed later. Further investigation of salivary gland chromosomes in II-III B hybrid larvae has led to the discovery of another translocation, which was not detected genetically. Fig. 28 shows two things, munely, the pa-rtial pairing of the duplicat:tng piece with :Lts homologue ne1::tr the chromocenter, and a translocation between the second Bnd the fifth chromocenter near the free end. The tvvo strands of the second chromosome are paired only in a little region at the middle. In the basal region, one -100- strand is apparently longer than the other, and the longer bears the inserted piece which partly pairs with its homologue in the third chromosome. It seems clear from the picture that the intercalatea. piece from the third consists of section 65 and a part o:f section 66. A careful arialysis further shows that the inserted piece is not directly attached to the chromocenter but to a light band not far from it. Since this band has no homologue in the "paired" portion of the third chromosome, it may be presumed to be the last band of the second chromosome before the chromocenter. The same condition is also shown in fig. 25. One of the unpaired strands of the second chromosome at the free end ends abruptly in section 56, and the other strand, including the free end, is partly paired vdth its homologue which is united to the fifth chromosome. The section excised from the second and.transferred to the fifth chromosomes includes the region from the distal part of section 56 to the free end. It may be noticed in both figi.n·e 28 and 29 that the piece is not united to the very tip of "j:.he fifth chromosome. Instead, a very small pi.ece involving only faint region is cut off from the tip. Where does this piece go can not be identified. It may either attach to the broken end of the second or simply get lost. Both genetic and cytological data. agree that the duplicating frag1nents in II-III A and II-III B overlap each other, suppressing the. gene .£=1:, which can, therefore, be located in the region comr::ion to both of them, namely section 65. When Sc pr duplication flies we1·e inter- crossed, they proved not only completely fertile themselves, but also produced viable homozygous duplications, as indicated by proportion of -101- ' different classes of flies shovm in table 94. Table 94. +or _o_r_ _s_c__E, or pr But ·when flies deficient +or ~~ x or __ S..£_ Dr 0'0' or or --·--·---=- Sc-pr pr or-Sc-pr or-pr T II-III A 105 46 18 4 T II-III B 128 41 34 4 ------. --~---~- for or were intercrossed . (table 95), they produced only or ond or J2E +Sc --.--- Table 95 ·-·-·------ ¥<:i> x - - - - - 010 or ------------·-·---·----·--·------~·- or or-pr =----=,-----.~,=~==;:=====::::.;;: T II-III A .. 59 164 T II-III B ________ ______________________ 158 .. offs pri:nc;. 42 The absence of v.'ild· type flies indic.s.tes the inviability of the homozygous defici0ncies. Incidentally, it may be mentioned that homozygous translocations of both II-III A and II-III B were fom1d to be inviable. T II-III A and T II-III B duplications were also tested for the recessive gene abrupt, which genetically is about 9 units to the right from or. The results of the tests are su:rmnarized in te.ble 96, Table 96. T II-III o~o x or .s.b pr n or ab or ______,____ + or-ab-pr or ab-pr T II-III A 105 55 92 8 T II-III B 52 24 48 8 -102-' and show tha.t .ab behaves like ,.m: but not like _.Q!, indicating that the locus ab is not inch1ded in the duplicat:Lng frae,rnent of either II-III .A or of II-III B. Since the gene .£!: has been shown to lie in translocations II-III A :and II-III B within the short inserted sections, vrhich does not cross over Fith the third chromosome, QI.' was used as the marker of the break in the third chromosome in tests for the locus of the break in the second. The results of the test crosses are given in tables 97 £md 98 for II-III A and II-III B respectively. The calmJ..l:xted cTo:3sove:c vvll::e in II-III A is 50. 7% between §ID. 1md .21:', • 52% between or and p, and 4,1. 5% betvveen p and ps, a.rid th2.t in II-III B is 3 .1 bet1;veen or and Sm, 40. 0% betvteen Sm e.nd ..£_, GJJd 20. S% betvveen p ancl ps. A cowpi:1d_son of these v1:ilues in sc;,are-Le crises -rdth those from the control given prev1ously (cf. tDble 71) renders it possible to conclude that the breek et the secorid chromosome :is near to locus pink in II-III A and between spindle fiber 2nd Sm in II-III B. The reduction of crossovers between p and ps in II-III B is due, as will be shmw later, to the pre::~ence of a vioble second chromosome du{Jlice,ting fragment ·Vil:.ich suppres,ses tbe gene pr:::, II-III .P: was further tested o.gainst the genes bi l2__ and ~. Tbo d2:G<1 given in table 99, showins; no croi::sovers in the first ~md second 1 118 2 64 182 0 0 45 57 515 79 0 0 42 41 226 174, 0 0 87 98 541 Table 97. T II-III A Sffi'."'or~=o-::::- ,-n .l. _.,.._ ,,..._.._ . ~-=·---·- --~--~,........,-$_..,. ___ ,._=_,,,,'-"'__,-~ ....... ---- ~... .._ ....... .-=----,.--~-----..- ·- 1--'I8 x or p- ·osd'd' ._ ................ ______ __.,._............ '-""'---..'5·.<8- ----.-..~..--.-.~----""---.-.----~~------='""--'" ~-~-·.--·--o-oo~--~··_,,........,,. ______.,. _,. _______ ,;.=----""-'->-=--=--· ___ ,,,_, ..... __ ,,,,,.__.-'"--"·-""==~,.... ...... triple Non-c:i:'Jsso~ cult. No. + Sm-or-p-ps _________.s=i;..:n,gl;:; crossovers ---~- ---,-~ ___g_ouble crossovers _____ ,___ reg~- . 1)2 1,3 ____?-;J,.'.?_ _ __ ~.&__l__ re_g~J~ ___ Sm m:>-p-ps Sm-or p-ps Srn-or-p ps Sm-p-ps or Sm-ps or-p Sm-or-:ps p ._.._. ,. _. . _,. ,. _ . ______ -----------~-------- .-....----------F-=<.~,~~----,---, ---·-----~ ---------,~-,-= .. ., ________. . ,. . . .___ =---"'~-C4-----'--"--=----,..._·,,.=-=-- --~--- ... - - - - - - - - ..._,__,.,.., ... .---~----,._,,.·_,,,.·=·-----0 .ao,.~=-_..-_,,,_ ... _ _ _ _ _ _ _ _ _ _ -~ - - - ----"" ________.,_,...._.... _ cros~E?..I:2_ l,_2 ,3 Sm-p or-ps tote.l --- ----- _... _,-... ,,...... -~ -..-= ....... _____ --- ---~-'-""'~--=--~-~ ---~---...--=~-"';...,...,....,..,_,,..=.o~"O..---.>==>=» -~ 1 56 13 5 15 0 0 8 23 0 0 l 11 0 0 0 0 110 2 9 4 5 7 0 0 3 8 0 0 5 7 0 0 0 0 44 5 40 14 4 12 0 0 12 16 0 1 6 11 0 0 0 0 116 4 50 18 6 12 0 0 8 27 0 0 8 8 0 0 0 1 118 18 57 n 0 0 1 568 -----------------..---~---~---- 115 49 18 44 - .......... 0 __________ 0 51 ......,, _______ __ ,,. 74 0 1 , ,., ---- I I-' 0 rn I T II-III :g 8 Table 98. -- . ..----.- -01":-sfi-3-~:o- ···,-'?'? ..... .1. x or o os ao .i.; --- ---·-----·----------·' ---- -------· No~-grossover§. cult. No. + or~Sm~p-ps •..-••--.- .i.: doub_le_~rossovers __reg. ±_.~- --""""---=--~------"---~·---,..-··---~----~, or Sm-p-ps ___ reg. ~-- 1,2 or-pL..;ps Sm or-Sm p-ps - _.__~~-----~-~----"-----~---~-""------~-=-----_..,-~-"""""-=~·~=*------=---·-~""--- ~l,l__~ or-ps Sn~p . . . =--..-...... ,,...,,,. . ___ ·~~~~ ~--J,~--·- or-Sm-ps p triple crossove:i;:_s_.~ 1,2,..§. or-p Sm-ps total ,..___,,_-m_..,..-..-.-.·---·------------ ,'»~-~--"'---.--=~----~==---"'-=-T-"<>_,_••~•-•==="-"~-=-·.--~=~---"--- ---~--~---- 1 27 23 0 0 22 21 4 14 2 0 l 0 2 1 2 0 .119 2 13 2 l 0 0 5 1 4 0 0 0 0 1 1 0 0 28 5 5 5 0 0 2 4 0 0 0 0 0 0 1 l 0 0 14- 18 2 0 1 0 4 5 2 0 161 --...... - ·---· 43 --~. 28 1. 0 24 50 -------·-- - 5 -----·~--·- - ------ I I-' 0 If::. I -105- ·region but 42. 0% between .IL. and 12§, suggest tbat the break in the second cbromorwme lies probably to the left of tbe locus bithorax. -th-<?. Finally, the piece excised f'roifl/\ second and trensfer::ceci to tbe fifth chromo:::~ome vms tested for r·ecesr:oive genes. The results of the crosses .c.:hmm in t<:'bles 100, 101 D.nd 102 suffice to show tbat the duplieating fragr!lent, cytologically incll~ding sections from 56 to 62, covers Tc:.ble 100. T II-IIt E! d'd' x p :rs or ~~ -----·--------JL.Jlf:L.QL_________~·~--.. --.~-- + 34 Table 101. T II-III ~ oa x p or ps bi n ----·--~2:~ bi________..._. _____ ... + )J-OI':.P.£l;:J?J 1)-0r-bi 57 50 16 Table 102. T II-III B O'd' x na. bi gl ~~ ----------lli'~. Pi. El--~.~·--"'-·r•·--..•-----...± bi-gl bi 30 the loci ps and gl. 42 10 The duplica.tj.on flies e.re abnormal in apyiearcmce, clici,i-2.cterized by rough eyes and shorter wings. When mated, they y;ere found to be sterile. Since Y-II C duplicating fragment suppresses only the locus ~, _gl can be loce.t.ed somewhere from the middle of· section 56 to the middle of section 59. Judged from the amo1mt of crossing over that takes place between the break cind. jQ ·in II-III C, the locus gl proba.bly lies close to the break of II-III B. -106- T III-J.Y_..L Trm1slocation III-IV Jl. is the only observed case of a non-reciprocal. tronsloc8tion between the third and fourth cbromosome. When Ill::-~; IA. males v;ere mr:.tecl to Q£ Qy fenwles, the distribution of offspring, as shovrn in t8ble 103, indicD.tes the complete viability of Table 103. LJJI""'."l~L.A c~ci' x or _Qy ~~ -------·----------·· or_±_. __. _____. ____ or + _ __±_ ~ 6' ==-··-37 41 _Qy_ -· ~ 6' _sg_s,x_ ~- _ _9].'_ ~ 6' 6' ·-·••;::;;:=..-:r-:::-..:::..:::.::-;::•.::;=~-==-:..::::,:-::::::::.~'.;:":"":;:--_::::.=:::.::::.-..'-=:-:::-: 31 49 21 30 trm1sloco.t.ion ind:i.vidlwls of both sexes. 20 41 However, a single mating, III-IV p, oci' x or ~~ produced 5 abnornwl Curly flies among the total of or Cy 546 (table 104) , indicating the presence of duplication indi vidu8.ls. "IJl!hen Table 104. T III..:J.Y_JI= 6'6' X or n ________________ g~1,'_C_y____________ + or-Cy .££_ Qy: 185 156 0 5 III-IV A males were me.ted or pr females, the result shown in table 105, or Sc pr Table 105. T III.:-IV A, oci' x or pr ~~ ___________ __?_?;:_Sc .PE______________________,. + or-Sc-pr_ 381 322 ur-Sc. 46 Sc_ 15 .2.!'.=R..9. 6 representing fly cmmts in four independent cultures, gave .1'.lc6 pr Sc abnormal f15.es, v·hich may be presumed to represent duplications. There were elso present 15 Sc m1d 6 or Sc norme.l flies, the cm1se for their appevr·ance -107- being lmlmovm. The reciprocal c:coss as shovm in table 106 produced 13 Table 106. T III-IV A oo X or or c5'6' ______,_________ ________...QL.§9_-2!'_ _-~_,._ . _., ____ ,~---- - - - - - Non-cro9so_Y..§.E..:?.. 8i_."Q._g1..§..s£.913.?.9:Y~.!:§___ douJ)le .S:..!~. Reg.2 _ _l~-- Cult. Reg.l _· _N.2_:-====:::::'."_::::::2:I;~J.:-E -~- .~~21--_!:I~Ji- .RL==.::?Ji::=::?_:·_:~o_:-~ __ ~::tal 83 1 1 104 0 5 5 0 201 2 126 97 0 1 1 0 0 228 103 106 0 7 3 0 0 222 333 286 0 13 7 0 1 651 11 - abnorrne.1 Sc ..,__, pr flies 1md no QI'. flies, indice.ting that crossing over is completely suppressed in this region. For the second region, namely between Sc a.nd J2E., crossing over amounts only to 2. 9%, showing consider§..c m:: flies were repeatedly a.ble reduct.ion as compared with the control. tested and folmd to be completely sterile. Homozygous translocation in di vi duals were f olmd to be inviable. The genetic tests of the fourth chromosomes involved in the translocation ShOi'i (tables 107 a.nd 108) that the genes ill_ a.nd j_ are Table 107. T III::IY...Jl <NJ' x na in j ~~ ..D§;._.QE_.J..____ ~--------------- + 9---a ____,._ ----------·-----------'" ___ ___________... _,_ 51 24 -··--~-- 20 ...... 35 .1 IJJ-IV_A <;?~ X na or in j 0101 -~ or__ in j ---------------.,. ___N_o_1_17 cro s s overs ______-l:_____·-=--=:=-.E~..=~J:;1E.:-j..:::::-::;== Table 108. 100 91 -108- not included in the duplicating fre.gment, and that the locus of the breakage is so close to in e.nd i that no crossovers are produced. Fig. 50 shows the heterozygous III-IV A translocation. A piece of the third clir-omosome from section 64 to section 70 is deleted enc'l interc21E.ted into section 86 of the fourth chromo:::;ome. The fact that thhi tr::urnferred piece of the Uiird includes the region common v·i th the duplication in II-III A and II-III. B, gives further supr.JOrt to the ideci_ that the locus for 2.£ is locali~ed in section 65. The considerc:tble length of tbe deleted piece nwy account for the sterility of duplications ano inviability of deficiendes. Fig. 31 shows the combination of III-IV A duplication and 1 r,arrow111 0101 x inversion. ma or in j ~~. rhif1 was observed in larva of the cross, III-]V A_ na or in j It may be noti.ced in the figure that the part of 1 the third chromosome from section 64 to section 67 is represented in triplicate. . Beyond section 67, the chromosome is bifurce.ted, n sinele strand above, representing the inverted strand, and a strand of norm2,l sec~uence below. The 'narrow" inversion sta1·ts at middle of section 70, but the III-IV A duplication runs a little over that point, thus the two overle.pping each other in a very smEcll reg~on. Since III-IV A c'l:uplicC1tion does not su1Jpress na,, onc1 neither does Y-III B duplication, the gene narrow must be loci:i.ted, somev:here in sections 71 or 7'2, within the inversion. Having learned that III-IV .A duplication is considerably longeJ7 than 'that of either II-III A or II-III B on the right side, the author m8.de tbe follm"<ing matings to find the genetic length of the duplication. In the cross of III-IJ_A or e.b pr males to Q.£ ab J2!.' femeles -109- { tDble 109), three Er durlication flies v.ere not. abrupt, indicating that Table 109. ----·--~-- T III-IV A ca x or ab pr ~~ or__gj;i_.:p.r_.___________ 22 70 3 the locus ab is suppressed by the duplicating fragment, c2.rrying its wild a11el. In tbe cros,s of III-IY...L~ mEdes )(, 9..Lf?..9. . . .P.r. females (table na or in j Bl 110), 8 Bl duplication flies appeared. However, these Bl flies,_ showing Table 110. T IIJ=I\f_ A ee x or S,,9.. J?K ~~ _________.P--2:.....9L. j in ____ ._!?}:__.__ Culture + Bl or or-Bl _j\T'l..! =='-"'·--=:. l 31 59 (4X) 32 3 2 54 74 (4X) 37 l x - du;Jlications less extreme 11 bl2.deness 11 than normal heterozygous B1ade fliAS, may be accounted for by supposing that t:hey C[ffTY t:v'iO wild a1lels a.nd one Bl gene. This fact suggests that the duplication cove1·s the locus B1. Fina]J_y, in the cross II~=l.Y-A-:- males to or Sc Ja fenw.1es (table 111), na or :m J _ · Ja Ta bl e 111.• _T _U:l:-1.Y~ . A-0~0' . x o-.L~ ,Sc _1:'1~Ei_L_. ______±__ __,._,____ ______. __01"_ __ _ _ .T§l~--,=-::::....-="'- Sc___ ,==·==='~ _.Sc_---=: 22 (5X) 16 26 31 x - duplications three observed Ja duplications showed more extreme "jC:Jggedness" than heterozygous ;Jg., inc3J.c[1·ting that the locus of the gene Ja is not included in the duplicating fraur1ent. Since .QA_ is not suppressed in Y-III B dupli- cation either, it seems very IJl'OrJable that it lies in section 71 or section 72. -liO- Cul tu.res No. 79 Bnd ~8 (Table 50) shmcr linkage of the genes loc1:1,ted in third and fourth chromosomes, indicating that translocations However, one may notice that involving these chromosomes are present. in the wild type and BE1.re cle,sses the males are more frequent than ,females, Bnd in the £!'. Qy and Ba or Qx_ clB.sses feme.les are more frec1uent than me.les. This led to the suspicion that not III-IV but Y-III-IV translocntions a are involved, and that the few wild type and Ba females and or SbL ancl Ba, ~ Jzy males are deficiencies and duplications respectively. To prove that, wild t;ype males from these cultures were crossed to or Qx females. The Again the majority of ~"ild type and results are shown in table 112. Table 112. Y-II~-I1 <3'6' x or Cy ~!? _____________ _QI___, _ _,________,, ___ + ~ Qi ~ Cy or ~ d' 16 6 Y-III-IV A 0 19 2 11 28 11 Y-III-IV B l 9 1 6 3 .._...__.. 5 0 ____1 ___ -------~·-..._~----·-··-_,,_......,._._.._ ~ or.-.C::z. -~--(il' d' ___,,_,__, ....,,,~ cla,sses are mHles, and or ,Q:y cls.sses are mostly females. presented in table 115 shows the same result. Table 115. Y-II~-IV ea x or ~!? __,____,_,_____ or,_-Ei__ + or-C,y: ~ '6"' __,.!?--er or ~ Y-III-IV A 51 222 258 175 0 0 0 1 Y-III-IV B 5 82 73 58 0 l 0 0 An experiment -111-' On the supposition that the deficiencies and duplications may cover some ·Of the third chromosome genes, the mEJ.les and females heterozygous for T-Y-III-IV A and B and for or Sc ~ were back-crossed to~ .m;:: females and males respectively (tables 114, 115, 116). Y-IIT-IV _ _ ..:::___ 6'6' TEible 114. or S_y pr _ + x or pr ~fi2 or Sc pr ·---"Q,___ . _6'_,_ _____2__ Y-III-IV A The 289 6' 579 Y-III-IV B 51 507 26 219 277 5 3 5 138 5 0 0 31 14 6 1 3 83 9 9 8 1 19 15 24: 11 1 3 146 69 40 76 35 6 14 487 1 28 58 20 13 2 6 10 5 2 25 25 8 3 4 17 25 17 5 36 39 110 137 89 ----·~~-.,·----·---,-·-·--·--·------·-·---·"··-....,--·-------,---.~-·-·-.o.-··-~--- Y-III-IV_.], ~~ x or pr ao- Table 116. _ _ _._.. _____,___________ ....2.£._§_C_JJE____, ____· - - - - - - · · - - - - - Cult. N 0 • Sing~e croSSOV§.J..13__ Doub]..J?_ c .o. li.eg.l He_g.2 1, 2 _ __ __±___ _gr-S_q=E_ __o.E___ Sc-pr --~E.:Sc· pr~-.§~_ ..9r-:J?:f ......-------------...-----_,..._., , _,__,_._. __ ,_ Non-crossovers ·--~-- _____ ______ ----~----~----- tot. 1 40 79 12 1 12 7 0 0 151 2 10 24: 1 0 5 0 0 0 38 5 9 22 5 0 15 0 0 0 7 0 0 0 18 7 0 0 256 4 7 4 --~--.--~- 65 .... ~~-----·_... 132 0 0 ____________ 18 1 ,_~-,--. 55 -112- results show that none of the third chromosome gene tested is involved in the duplications or deficiencies. Moreover, the frequency of cross- ing over in the third chromosome is normal in Y-III-IV A, while in Y-III-IV B it is reduced ( 7. 9% between or and Sc and 16 .4-% betvreen Sc end pr) • Similar tests were a.rr1'mged for the fourth chromosome (table 117); again neither of the genes tested (incomplete and jam1ty) showed ! Y-IJ,_:i:-T1 (]101 x na in j <?!i! Table 117. --------..:::n~a.~.~lI.L.J _ _·-----·--·- __t__ na-in-,i d' - 0"' d' Y-III-IV A 31 86 90 29 Y-III-IV B 25 44 127 30 -------·------- behB.vior indicating that these loci are not included in the duplications and deficiencies. Finally, the test with the fourth chromosome gene tangled 0 (tables 118, 119, 120) was successful, since in both translocations it is suppressed in duplicDti.on individua.ls, and manifests its elf in deficiencies. Table 118 • ---:--.z--·· Y-III-IV A 00 "" x na t g 3 ~<? na tg° Cy _j-__ na-tg3-.Q;y: na-C:y: -· a !i! a <? . a <? --··--~-·--·--·--------------- . 30 9 Table 119. 38 12 6 2 Y-IIJI-IV B 6'6' x fla tg3 Cy<?~ na in j -+---------y;;-----·-ti3 ____ ---~~-<3' ____ _J_~_ 0 19 20 2 ~ <3' 6 0 ----·-·-·---·----·---------·----- -113- ·---·--------------·----~-- --------------·-------~-- 44 81 8 0 Further study of these two translocations was carried through with the aid of the cytological method. 'l'he salivary gland chromosome configura.tion for Y-III-IV A is shovm in. fig. 32. It shows that the part of the fourth cb.romosome including sections from 9'(/ on to the free end iEl atta.ched to the chromocenter. The part of the cbromocenter to which this section of the fourth chromosome is attached is associated with the spindle attachment of the third chromosome.· In the light of the genetic data given above, the probE:ble fea.ture of this translocation may be that each arm of V-ohaped y...:chromosome receives a. tr~msf erred piece, one from the fourth chromosome including from sections 9fJ on to the free end, and the other from the third chromosome including a part of its heterocbrom~tic region. Fig. 33 represents the heterozygous Y-III-IV B translocation. The third chromosome is broken; and the basal part is attached to the chromocenter. The major part of the third from section 64 to the free end is attached at the junction of sections 93 and 94 in the fou.rth chromosome. The piece of the fourth chromosome involvinr; section 94-99 does not unite with the broken end of the third, but is attached independently to the chromocenter. In another larva, a duplication for the broken off section of the folirth cli..rornosome is found as shovm in fig. 34. The duplicatinr; fra.gment is attached to the chrornocenter. The simple interpretation of the situa.tion in this tr1mslocation, therefore, is tba.t a. long piece of the third chromosome is transferred to -114- the fourth, a section of which in turn is attached to the Y. Probably Y has also lost oa se.ction vrhich is lmi ted with the broken end of the third chromosome near the chromocenter region, but this has not been esta.blished directly. !Anyway, the cytological analysis seems to fit the interpretation of the genetic results given ebove, namely that the fem2.les vii th tilted wings and mhmte bristles represent deficiencies Q Y-III-IV B ma_es 1 I n d ee d , vv.·h en - ··---·-· wer-e mat e d t o p or t g 3 f· ema1 es, or na or in j Y-II~-I~ B.males were mated to na tg3 Cy females (tables 119 and 120), na in J some !1?;.3 females with tilted wing and minute br:tstles were produced. Duplications and deficiencies in both Y-III-IV A and Y-III-IV B have been proven to be fertile. T IT~III-IV This is a translocation which involves t:b.ree long autosomes. As shovm by the results of the crosses given in tables 121 ancl. 122., these translocations produce viable duplication for _Qr. Table 121 • T II-III-IV- A cJCJ >< or ~~ Cy ~~~~~~~=Ba 9r + 34 Ba-_Q:y_ Ba-or-:-C.Y _L__-5!._____L ____::_"__ 24 Table 122. 60 ---·-·~ _ _CJ_ 10 43 8 T II-IIJ:...IV_A o'cl' x p or tg 0 00 _J?_ or 'T'T tgB"" Cultl.1re No. + p-or-tg3 p-tg3 1 136 109 41 2 32 54 6 They have -115- minute bristles and rough eyes. 1i~nen tested, they were proved sterile. In the salivary gland chromosomes of this heterozygous tr1msloc~'tion, a complicated configuration has been observed. shows all that can be reported for this translocation. Fig. 35 A long piece of the second chromosome from section 51 on is translocated to section 90 ')? the four th chromosome. A long· lJiece of the third chromosome from section 66 on to the free end is tra.YJ.sf erred to section 44, of the second chromosome. The basal portion of the third chromosome, though not clee,r in the figure, probably receives sections 4 7 and 48, which a.re paired with their homologues, from the second chromosome and free end from the fourth chromosome. As shovm by the loop region of the fourth chromosome, a part of it ct:m be homologizecl with sections 92 and 93, indicating an intra-chromosome,l translocation in the fourth chromosorne. Since this tra.nslocation . is too coml)licated and has proven not of much use for construct:Lng cytological maps, it was not attr,;1 1pted 1 to wor·k out details of various brealcs. However, the duplication Ba _Qz and p tg3 flies shown in table 121 and 122 prob::o,bly represent the duplication of the whole rebuilt chromosome, consisting of the third chromosome bs,sal end (including the locui:: or), sections 47 and 48 of the second chromosome, and the free end of the fourth chromosome. T Y-II-UJ.::IV _A As shown in t2.ble 50, strain No. 8 gave almost exclusively wild type males and Ba or Cy fenmles, indicating a translocation involving Y, second, third and fourth chromosomes. Further results of tests (table 123) suggested that du9lications or deficiencies are not viable. -116- 0 130 140 0 Heterozygous translocations seem, howeveJ~, to be completely viable. Salivary chromosomes of thiEl translocation have been studied and found to involve very complica·i;ed rearr1mgements. have not been worked out. in fig. 36. The details An outline sketch of one figure is shown It can be interpreted so that the second chromosome is broken into three pieces, the short free end is transferred to the fourth chromosome, a long middle section is intercalated into the third chromasome, arid the basal portion seems to receive a long inverted segment from the fourth chromosome. The very tip of the fourth chromosome is removed, and probably united to Y. The purpose of presenting this sketch is merely to show that incli vidm1.ls heterozygous for such an enormous amount of chromosome rearrangement can still be completely viable and fertile. In view of the i:r:-regular distribution of different classes of offspring obtained from the strain No. 174 as shmm in table 50, salivary chromosome configurat:ton vms irmnediately examined. Fig. 37 -the is one of"" two urrn.sually clear pictu:ces which vrere found for this hetero-~ zygous translocation& A very long second chromo::iome strand is trans- f erred to about section 67 of the third chromosome. . fro7•tJ)./2 cJw,_ 67Uh~ -&.-cl The section of the J./1 ffiverled..oni.er, tl~:i:ne-=-t:he region from section 68 to 7~ansf erred ~ -117- S::l.! voted oi def• to section 96 of the fourth chromosome. A short fourth chromosome piece is transferred to the fifth chromosome. Since the genet:tc d8.ta (table 124) incJic.~1.te that Y-chromosome is involved in this translocation, it seen1s reason8.ble to assmne that a piece of Y-chromosome J_:3 trm1sferred to the blf"oken basal reg:Lon of the second c:hromosome. 2 65 80 13 l 31 5 21 The results presented in table 124 show a number of different exceptional classes of flies. In the light of the cytological observe.tions, the interpretation of the respective classes of individuals might be as follm'TS: wild type females may rep:cesent non-disjtmct:Lon (XXY), p or tg 3 males m;:;i.y rep1~esent the other non-disjunct:Lone.l class (XO), p Qr males may be XO bearing a duplicRtion for the transferred :part of the fourth chromosome, 111hich suppresses j;.g 0 • tg3 males may re2Jresent deficiencies for the _pE,rt of the fourth. p or females may re:i:,resent XXY vrith a deficiency for the section of the folll'th. interpretation may be entirely vvrong. The ·;:;i.bove Nevertheless, it cannot be r1oubted that the locus of the wild allel of 11;3 is locn.ted in the broken off part of the fourth chromosome l~'hich is transferred t0 the fii'th. In two p1'ev:tous pe.pers (Tan 1935a, b) the author reported that the two races of Drosophila pseudoobscura differ in four long inverted sections, one each in the left limb of X-chromof3ome, right limb -118- of X-chromosome, second chromosome sncl. thiTd chromosome, and in two consta:..rJ.tly unpai.,red regions in the left limb of X-chromosome. Since the publication of the above, the two very short vnpaired regions in the left limb of X-chromosome, ·which v;ere once suspected to be inversions too, have actually been observed paired in the hybrids. of the two races b~r Dobzhansky anc1 Tim (1936). Figures 38 and 39 show interracinl inversions of the second chromosome. The lower limit of the inverted section lies in the intersection between section 51 and section 52 (fig. 38) and the upper limit is within section 56 (fig. 39). That gene Ba can not be trans- ferred from race A to race B (unpublished data of SturtevD.nt and Dobzhansky) can be acc01mted for by the fact that the locus Ba lies within the inverted section, as has been indirectly demonstrated in II-III A translocation. Fig1.1res 40 and 41 illustrate the interracial inversion in the third chromosome. The upper limit is shovm (fig. 40) to lie within section 78 <md the lower limit near the intersection between s0ctfon 70 and section 71 (fig. 41). The study of Y-III A and Y-III B trRnnlocations has demonstrated th0.t the loci Sc and pr lie in a region from section 73 to 78, ·l"!hich is almost entirely included in the in"ceTracie.l inversion. This may explain very vrell the fact that genes Sc and pr can not be easily trimsfe:rrec1 frorn race A to race B. On the other hm1d, gene or, which has been located in section 65, ca11 be tr1msferrec1 from one race to the other very easily. -119-. The previous section has present8d the evidences upon which various genes are located in the salivary chromosomes. Fig. 42 shovrs the composite _pictures of the second, third and fourth chromosomes of Drosophila pseudoobscura, and the various breaks observed in the translocations studied are indicated by the lines above. Belovr each chromo- some are shovm the corresponding genetic maps which represent the spatial relations of the genes in terms of the crossover units. very kffl-e... In the second chromosome Sm, giving al.moot no crossing over viith the break of T II-III B, probably lies ve:Ey close to the spindle attachment. Judged from the fact that the break of T II-III A does not reduce the frequency of crossing·over in the region between pink and bithorax on one hand and pauciseta on the other, the gene loci for both bi and Jl may be localized to the right of the break of T II-III A. Gene £!., being suppressed by the duplicating fragment of T II-III (V) B and not by that of Y-II C, must be located somevrhere between sections 57 and 60. The gene ps, being covered by no other du- plicating fragment tha11 Y-II C, lies, consequently, closest to the free end of the second chromosome. In the third chromosome the gene or has been localized within a narrovr region of section 65, which is in common for duplications II-III A, II-III B and III-IV A. Genes Bl and ab, being suppressed by III-IV A duplication but not by that of either II-III A or II-III B, are located somevrhere between sections 66 and 70. Since Ja is not covered by either Y-III B or III-IV A duplicating fragments, it must lie in sections 71 or 72. Sc a.nd pr, which are included in the duplicating -120-. frag111ent of Y-III B, but not that of Y-III A, me.y be located somewhere from sections 7'3 to 78. The knovm locus nearest to the free end of the third chromosome is srr, which is included in Y-III A duplicating fragment. Compa.ratively few genes are knovm in the fourth chromosome. Near the spindle attachment is the gene in. The gene, ,j, being covered by Y-IV D duplication, is located in sections 86 to 88. Since the locus ~5 is covered by the duplicating fragments of Y-III-IV .A and Y-II-III- IV-V A, it must lie to the right of section 96. The loci for genes..Qx and Ro, knovm to lie .to the right of tg3, may be located very near to the free end of the fourth chromosome. A comparison of genetic and cytological maps of the autosomes of Droso1)hila pseudoobscura, shovm in fig. 42, reveals several interesting fe.cts which seem ·to agree fairly •Nell -~1 rith the generalization,s resulting from study of the meta.Phase chroma.some maps of Drosophila melanogaster by Painter and Muller (Painter and Muller 1929, 1 Painter 1931, Mul lAr and Painter 1932) and by Dobzhansky (1929a, b, 19302., b, 195la, 1952b,c,d), and of the salivary chromosome maps of the X and third chromosome of the same s1)ecles recently est~1blished by Painter (1954a, 1935). In both melanogaster and pseudoobscura, the linear seri- ation of genes has been fovnd identical in the genetic and the cytological m2.ps. This corrobo-i:·ates the hypothesis of the linear arrangement of genes V'ithin the chromosomes which was advocated by Morgan Dnd by StuYcevant, 'Omd vrhich has been one of the main vrorking hypotheses in genetics. -121 It has been fovnd in Drosophila melanogaster, in both metaphase and salive,ry chromosome maps, that the relative distance between genes in the genetic and cytological maps appeecr to be widely different. T!1.e genes lying near the spindle attachment are relatively much farther apart on the cytological then on the genetic map. Fo:c genes lying in the middle of chTomosome the reverse is observed. Such discrepancy is due to the variable frequency of crossing over per unit length in the different parts of the chromosomes. As shovm in fig. 42, the positions of the loci in the three autosomes of Drosophila ])Seudoobscura seem, in general, to correspond to crossover values of the genetic maps. It should be taken into account, however, that in most instances we have been able to lJlace genes only within general limits of several sections, and that we knovr nothing, at present, regarding the distribution within these limits. Of the three chromosomes, the map of the third presents some evidence that crossing over occurs less frequently in the spindle fiber r~gion than near the free end. In the salivary gland chromosome, the locus Scute is a)Jout equ:Ldistant between the loci of orange and crossveinless. On the genetic map, hovrever, Scute is 28 .8 m1i ts apart from orange but 39 .6 "Lmits from crossveinless. This is appa.rently due to the higher frequency of crossing over in the region between Sc and QY than between .Q_c and Q1".... In regard to the second and fourth chromosomes, the evi- dence is less conclusive, partly due to the presence of long gaps between the loci of Smoky and bithorax in the second chromosome, and between the loci incomplete and jaunty in the fourth chromosome. Still, genes ..:.122-· pink :md bi thorax in the second chromosome appear to lie relatively farther to the right in the salive.ry chromosome than in the crossover ma.p, indicating that the frequency of crossing over, in terms of the cytological map, is higher in the region betvrnen bithorax and the free end than between b:Lthorax and the spindle att~3-chment. The same explrn12- tion may &lso be applicable to the fact thgt the cytological location 'Z of the gene !:..g0 in the fourth chromosome is relatively farther to the right from its )OSition in the corresponding genetic map. A survey of breakage points in those translocations in the tli..ree autosomes presents an interesting picture. The frequency of breaks is not necessarily proportional to the length of' a chromosome. According to Muller and Altenburg (1930) and Patterson, Stone, Bedichek and Suche (1934), the frequency of breakages due to the X-ray treatment is roughly proportional to the length of a chromosome. This is true with the V-ohaped Y-chromosome of Drosophila pseudoobscura, ·which takes part in the transloca:tions more frequently than any autosomes. But runong the three autosomes, the third chromosome is shortest and yet more breaks were observed in this than in other two autosomes. probably, a different factor is involved. Here, According to the unpL1blished data of Sturtevant and Dobzhanslc-y, inversions are found most frequently in the third chromosome in the different strains of Drosophila pseudoobscura and Drosophil::, miranda, Dobzhansky and Ta.11 (~ 1936) have fovnd that the thi:td chromosome underwent m:?ximrnn changes between the two species. All ,sources of data seem to indicate that the third chro- mosome is more susceptible to breakages than the other two autosomes. Assuming that the origin of the different kinds of chromosome rearrangements, such as inversions, intra-chromosomal trm1slocations, inter- -123- chromosomal translocations, deletions, etc., involve a si.111ilar mechanism, we may be led to believe that there is a definite inherent property in the third chromosome that rendered it more easily breakable. In an attempt to explain the distribution of a majority o.f brenks in the spindle attachment region of these chromosomes in induced II-III and III-IV translocations in Drosophila melanogaster, Patterson, et al (1934) and Painter (1935) suggested that yhe :;_:Jhysical be.sis for the exchanges of chromosomes is the close contact or proximity of the part,s of chromosomes involved during or immediB.tely after radiation. Since the spindle fiber regions of chromosomes are sup9osed to be closest ·bo. each other in mature spermatozoa, which are the main so1n·ce of translocations obte.ined by X-ray, the chances of exche.nges taking plctce in these Tegions sho1.1ld be bette:r. than in the regions away from them. This is true in third chromosome of Drosophila pseudoobscurc;, as shown in fig. 42, in v1hich more breaks are located near the chromocenter than in the free end region and the middle region combined. In the second and fourth chromosomes, however, such relation does not seem to exist. As e, matter of fact, three of the :four Y-II translocations involve breakages within sections 48 and 49, close to the middle of the second chromosome, :;i.nd four out of five Y-IV translocB.tions hB.ve breakages yrithin the sect:tons 91 to 94 in the fourth chromosome, far away from the spindle attacbment. These observations suggest on one hand that it is not always that majority of breaks fall j_n the chromocenter regj_on, a.nd on the other hand tJwt there may exist a definite relation between parts of particular chromosomes at the time when chromosome ret?,rrangements are induced. -124- Probably, at the time when sperms are irradiated, the chromosomes may form a more or ,less regular pattern, so that exchanges would occur mostly in the regions where chromosomes come in contact.. Such contacts may be in the s1Jindle fiber regions, middle regions or free end regions, depending on the arrangement of the chromosomes in the pattern. On the suppo.sition that the loci of exchanges in chromosomes are due to proxirn.ity of contacts in the mature spermatozoa, a longer chromosome should be subject to eJ_ terations mor\3 frec~uently than shorter chromosomes. It is possible and probable that the high freq11ency of breaks in the third chromosome is due to the for·mation of loops, fo1~ indeed the wide occurrence of inversions in nature and presence of an inversion and three excisions rnnong the 22 translocations obtained by irradiation furnish some evidence that loop formation is highly char- -the act8ristic of;\third chromosome. Translocations and inversions modify the order of the genes in the chromosome, produce nevv linkage relations, end alter the mode of inheritance of the genet:tc factors located in the chromosomes involved. They need. not, however, affect either the munber or the kind of the genetic factors, and therefore individual heterozygous or homozygous for these chromosome ree.r:r2ngemei1ts should be normal in appearance a.nd in viability. These theoretj_cal expect~1.tions are, hovreveT', l1ot alYrn:ys realiz,sd in both D:cosopbila rnel2nov.ster and Droso)hils Psm1doobscura. The first translocation discovered in Drosophila mele.no- gaster (Bridges 1923, Bridges and Morgan 1923) :·i;-poduces in heterozygous condition a domin:mt effect on the eye color 8.nd is lethal when -125.:.. homozygous. Muller (1928a) found that a majo:city of induced transloca- tions are invif3-ble in homozygous comUtion. Muller 1 s findings were corroborated by observations of Muller ond Altenburg (1950), Dobzhansky (1929b, 1930a, 193la, 1932a), Dobzhe.nsky and iSturteveJ:it (1931), Oliver (1932) and many others. .Al though some tr;:mslocations are viable 8.nd normal in 2.ppearm1ce in homo·zygous concli tion (Dobzlw.nsky l929a, 193la), this is an exception rather than the rule. Not inf1·ec:;_uently translocn.- tions produce visible external effects (Muller 1930, Burlun·t 1931). I\s i)o:Lnted out in previoLH3 sections, indi vidiJ.als hetero~~y- gous :for trc:.nslocations are mostly fully viable and fertile in Drosophila pseudoobscura, regm:·c:Uess of the number of chromosomes involved. This is partly because the techniclue used for obtaining trcms1ocations would tend to eliminate the inviable or poorl;}r viable heterozygous translocations. Bi:lt in only one case, namely T III-IV B, homozygous translocations are viable and no1·ms.l in e.ppeo.rence. The viability and fert:Ll:i ty of heterozygous duplications and deficiencies dei~Jends primarily on the length of the piece involved. Duplications for more tha:11. half of the length of a chromosome, such as Y-II A, Y-II B and Y-II D, ore non-viable. Deficiencies 2re, in general, inviB.ble, except for a very smB.11 section. Thef3e observations seem to agTee with thosl~ on Droso~1hila mel::nwgaster. The behavior of heteroploids may olso vcn·y y,:Lth diflei:-- cnt TegioriD of a chromosome. In the third cbromosome of Drosophila :pseucfoob::-:curr:., T II-III A :'md T II-IIJ B clupliccd.ini::; pieceo, eovering the sr:;ctj ors lyinc; close tc tho s;::_-:iYJr!le c:ttt1cl1ri1ent in the no~Tli'.1 cf!To- mosome, ere vj cb1e encl fert:i.1e in both heteros~7 gouE: 1:md homozygous -U'.6- conc~ition, tbe correspondirg defj_c:i encie::· Dre 1-:o-v,-ever viEble nncl fertile of T Y-III A, v·l1ic:h il'.lcJ.11oen tbe frPe end of tL'.e third chro1r.osome, <:ire viable only in hetero~;yg01.is condii-,ion, 2nd mo:reove:r they c'l'e sterj_lp. 'I'be deficiencio:c~ cir-c non-vic;ble. Sinee -t.be lengths of these c111;::lic2.ting fr;·.grnents a:i.:-e e.:;_::proxim1; tely the sume, there moy be a difference betr een tr·e :JE:.rt of cl':ron1osorne neer si1incUe stt<:ich:ment c:rncl the.t near the free encl with respect to the vic:,.bility ~1.nd fertility in duc1licatioll and def:i.ciency. It is, however, j ntere:::-l:.:l.:ng to note th2t hetm-·oz.ygous defid.c:·ncies for eve:n so short e piece of tbe tbird chromosome HS Y-III A are leth~:l j_n pseur3.oobscurc-1, end yet in Droso~Jhila miretnde. rn21les ri thst<::r1d a deficiency for the· whole of x2 not only v:ithout c'IJP<·Tent harm, b1Jt even without IPUCh mocUfj.cEJtion of the morphologicc1.l Emd physiologSince the x2 E1nd III icn.l chELr~wte:i.:-istics (Dol;zl::ansky cmd Tan 1936). ure rwrtly homologous c:ncl both include the region of Y-III p_ tnmf3location, the possible e:iq.)1£. natioE wrn:i.lc seem to be, <S pointed 01.Jt by Do1nhcnsl:.y 1 nnci Tmi (1936), t.hot, Clespite tlieir npperent clo.se sirnilDrity, mir2.nc1a. Vie:,'e described in Droso:i.Jhila melr·nogaster, encl 2 mr. joTity of these YeJ:'e interpreted to be s:LmplE1 ones (Huller 1930, DobzJ·1.:::n,sky 19olb). But e:1fter the intr·oc1uction of tbe study of sali var-y gland chromosomes, this interpretation 1N2s proved to be erroneous, since most of the presumed sirnrJle -127- trcnslocat5 ons 1nere found to involve .s.n ex:ch::1nge of very short sections of one chromosome for relE1t:Lvely long sections of other cbromosorne. Indeed, if a very short eection containine; no 1oci of known genes is tron;::,:fer:red from one chrorn_of:orne to another, tbe translocatioYJ in which such a transfer hes ts ken place n1e.y t:1i:;i:iee.r to be a simple one, both 1rhen sti1c1ied gen0tically m1d rhen studied cytolo[:;iCl'l.lly in met8.~ hc-:se ple.te 1 chromosomes. Thi::: fa.ct has led some rnJ.thors to asst1JD.e that ell trBns- locEtions are r-eciprocal, and no simple tr<cu1slocci:t.j_ons occur. The three cc:i.ses of non-reciprocal tr<:Hlf31ocE!tions described in tl'e iJrevious sect:.on, eS}'eciell~T T II-III P_, vrhich has been very corefully ~-;tudied c:ytologica.1ly, show this e:x:tr·eme 011inion to be erroneous likevdse, though these Ci'Wes ore like the usual reciproccl tr~mslocutions, in that they do not involve m1ionf~ m~cept a.t breakage points. How such a transloccition 1nhich involves two brenkage points in one chromosome and only one in the other CD.rt occv.r is not known, though Kossikov and r!bller (1D?i5) gave a hy~:iothet:J_ca1 scbeme for it. Comparison of genetic m2ps of the chrorno::wmes of different species hc•S been possible in ver·y few cases only due to tbe extreme lt:1b0Tiousness of this method. The best exumples are Drosovhile rnelano- go.ster 0.nd Droso_phile sirnulmrn -dd.ch vrere fomid to diffcT in a long inversion in the third chromosome (Sturtevant c-ind Plunkett 1926, Stlir-cevv.nt UJ29) • Recently these species were reinvestigated with the aid of the salivary glan.d chromosome rnetl:wd, vdth the result ·Qhat some minor alterations of the gene 8.lignment vrere detected besides the third chromosome inversion (Pate.u 1935, Kerkis 1936) • The genetic rnsps of -128- tb8 tv 0 species DTe in perfEc)Ct 1,·greernent vdth their cytological abnor1 n1ulities. ) ! ;•. ·~~-},;./v,·- Me tz (1916) 2.nd Lancefield (1922) have QXl suggested that l one arm of V-sbuped X-chromosome of Drosophila pseudoobscura corresponds to part of the rod shaped X-chromosome of r:mch s:;Jecies as Drosophila me18nogc.ster. Koller (1952b) further :=mggested that tbe other ~1rm of the V-sha1Jed X corref1ponds to a portion of one of U1e e1Jtosor:1es in those Dpecies (such as melenoe;aster 'f witb a rod-sh;::ped X-clD~omosorne. More recently Grev' ancl Lrnny ( 1935) attempted to homologize part or t::1e whole of the second cbromosome (third chromosome of Crew and Lmny) of Drosorihila pseudoobscErH to the left 1:1rm of the V-:Jh1:<11ed tbird cbromosome of rnelanogaster, ;::no fourtb chromosome of pseudoobscura to the right arm of Vshi:iped second of me1811ogaster. In view of the facts thnt relat1vely fevs genes are now knovm in Drosophile. pseudoobscur2. ond that the two spco.cies ;::re not cross;::ble to effect direct test, it seems to the author tb2t Dttempts to establish the homology of genetic nwps of the tvJO species ;::ire ratber hazc:rdous. Nevertheless, it is possible tbat a pa.rt of the third chromosome of Drosophila mel;:,nog2.ster is homologous to a pert of the second cbromosome of Droe:ophil!::1 pseudoobscura. Thi:; guess is based upon the evidence that most of tbe lmovm genes found in the lB.tter, such as .:e_, g]. ;:i,nd Q.i., proc1uce similar exterm1l effects as genes reported in the former. 'I'he gene Smoky of pseudoobscm7ci. and tbe gene del tci of melanoge.ster resemble each other phenot;y:pically, and 2Te porheps homologous. Bare of pseudoobscura and Stubble of melanogaster, both being domine.nt and affecting the sbortenlng of mfi croclrnete, may likewise be -129- the some. However, t.be sequence of these genes is not the same in the two species. Like the chromosome differences betvreen Droso::,~bila pseudo- obscura and Drosophila. minmcfa. the change in seciuence o:f genes nw.y be due to a number of rlterations vd.thin the chromosome, such as inversions or intrc:1.-chromof.wm2.l trnnslocations. In dj_scuE.;sing the distribution of sterility factors in terms of cytologice.l maps, j t iR interee:t.:i.ng to note tho.t tbe parts of chromosome carrying inte1·rt3CiEl inversions are Jikely to contnin numerous or porverful sterility genes. Using testis size as an index of tbe degree of' tte der1c::.rture from tlie normal structure of tbe testis lead5nt, to sterility, Dobzhansky (1956) has shovm that there exist in each of the X-chromosome, the second chromosome end the third chromosorne of Drosophila pseudoobscura more than one genetic factor causing the sterility of the interrtCJdBl hybrids. Moreover, he found that the pe.rt of second cli..romosome carrying the gene Bare and tbe pe.r-t. of the third cbromosome currying the gene purple are more effective in producing sterility as compared with the part of the second carrying the gene Smoky and the pa.r-t. of the third carrying tbe gene orange. Since it is now lmovm in the cytological maps that genes Bo.re ~:nd purple definitely lie within the interr~;cic:l inversion,s o:f the second and third chromosomes respectively, arn'l that the genes Smoky and onmge, lyins close to the spindle o.ttochrnent in their respective chromor.~omes, 2re located quite fe.r oway from the inverted regions, the re1a.tion bet1r:een interTRCia.l inversions cir10 in ere< sing effectiveness of sterility factors becomes e.pp0.re11t. -130- In 00 far DS the clirect cnusation of hybrid sterility by interrecie.l inversions is concernec'l, it has bee11 directly Bnd jndirectly clisc:1pproved. Directly, it hclS been shovm by Dobzhr:!nsky (1956) thot the fourth chromosome plc:cys a part in C£ntsinc the sterility of the hybr:Lds, deGpite the fact that this chromosome is simil2.r in nrrenge- ment in both race A anr! nace B ('I'm1 1955b). IncJ:ixectly, Bgain it has been shmm by Dobzhansky (1955a, 1934a) tha.t tbe doublinc, of the cllrornosome complement in tbe fr_,_terr:,.cial hybrids in Drosophile, pseudoobscura does not lead to an incre;:rne in the frec~uency of cbromosome pai:rJn~~ at meio:1is, nor to rc[;torB_tion of fert.il- i ty, indicating thnt sterility here is not duo to difference in c;ro:ss chromosome structure. To accormt for tlrn re1etion of parts of chromo:::10n1NJ ossociDted vii th inte1-r:cJd.e.l inversions and the incre[· sing offectiveness of proclucins sterility, tvro explc:nDt:i ons seem to be possible. First, since most crossing over in the hybrid occ1Jr in tbe region betv•een spindle s_ttac:b1nent end the lower limit of inversion, the resul tine; pnrt of cbromosome including inverted region is in most cases considernbly longer than that ·without it. As a consec~uerice, the i.ncree:o;ine; effectiveness of producing ste1·ility in the hybrids on the po.rt of Bci region Fnc1 £!'. region is due to the length of chromosome section j_nvolved rc>.t.her than t11E presence of in•1ersion. Second, the possibility that sterility is sorrtebm•: indirectly connected ·\id.th these interred 2.l inversions is also not excluded. The gene mut1::i.tions t}•at CG.use ster".li ty mic;ht have been in some manner connected in their oriGim-; 1pJth the origin of the inversions, -151- . just a.s some mutations, or position effects, are connPcted with translocations and inve;rsions. .SUivIBilJ\RY 1. The genetic maps of the three P.utosomr~B of Drosophila pseu6o- ohscnra are e:hor,Jn in figure 42. A. nle seconc~ chron1of~ome is 92. 8 units long, and the sequence of genes is Smoky, bj_thorcix, pink, Bare, gl2.ss e,i1d p8.uciseta. B. The third chromosome is 68 .4 units long, a.nd the sec:uence of genes is or1mge, Blade, abrupt, Je,gged, Scute, purple and crossveinle::.1s. C. The fourth chrornosorne is 69.2 m1its long, and the sequence of genes is incomplete, jaunty, te.ngled, Curly and Rough. 2. Twenty-tvro tr1:mslocDtions have been obt10dned with the aid of X-rs.y. They involve O.iff ererit combinat:i.ons of chrornosomes, exclusive of the X-chr01nor.;ome, as follows: 4 Y-II transloc101tions 2, Y-III II 5 Y-IV 11 3 II-III " 3 III-IV " 2 Y-III-IV 11 -132- 3. l II-III-IV transloc2.tion 1 Y-II-III-IV II 1 Y-II-III-·IV-V 11 Most of the t:cnnsloce,t:i.on,s that involve tbe Y-chromosome give viable incliv:i.duals hetero2-:;ygous for duplications. They were tested f'oT the surrpression of genes; tM.s method ie very efficient for the ...... .J localizstion of genes on the cytologicc:1.l maps. 4. 'l'wo of the II-III transloct:itions ;:md one of the III-IV tr~ms- locations are non-reciproc2.l. They involve excisinns of lJieces of tbe third cb.romor:;or0e :near the spindle attach111ent, includin:.:; the gene orange. The exci:oJed piece :Ls inte1·cciJ.a.ted into the second chromosome in the case of the II-III trm1slocr.tions, and into the fourth ch.romosome in 1 tbe case of tbe III-IV trar).slocci.tion. Since the duplication flies in all the e.bove three cases suppress tbe gene orenge, the locus for it has been determined to lie 11ithin the limits of a few bands in section 65 of the third cbrornosome. 5. In reciprocal trr:nslocGtions, the hetero~1loid flie~3 carrying d11plic2tion for a sectj on of one cbromosorne nece::::sarily carry also a deficiency for a section of another chromosome. pletely inviable in e.11 cases studied. Such flies ~n·p corn- The genetic tests for breeks her·e, tbPrefore, are limited only to crossing over PxperimPnts. 6. In only one car~e, namely T III-IV B, individuals homozygous for the trenslocation are vi<:tble, fertile, and normal in <:1.ppe1::.rm1ce. 7. The salivary chron1oio;ome config1J.retions of all heterm-;ygous trm1slocations v;ere studied for the determination of the exact nature of tbe t:r:.:rn.slocetions end of the points of breri.lrn,ge. 8. By combining the genetic do ta. and cytolozical dote for 22 trcms- loc21tions, the salive.ry chromosome maps of the three <:mtosomes a.re established, EiS shown in fie,lJ.re 4t;?., ith the various breaks of tr~msloc21tion 1· 1 indicated by the lines above. 9~ t~1e Due to 'the irregula.r distribution of breE:ks nnd genes Elong genetic nmps, most genes are located in the sali W:J,ry chromosomes only within general limits of sever2-l sections. 10. Comparisons of genr':tic end cytologiceJ_ maps of Droso::)hila pse1.:t- doobscl1ra h<:ive established the following fE .cts: 1 A. That the genes are ci.rranged in a lineB.r sequence. B. Th8.t the morphologice.l positions of tbe loci in the three rn.Jtosomes roughly correspond to crossover vci.lues on the genetic maps. C. 'I'hat the lengths of the salivciry chromosomes are fairly proportional to the lengths of the genetic maps. D. · 'I'hat the genes lying nesr the spindle attachment rre relBtively ~ farther apart in terms of the CJ·tological than in terms of the genetic map. F. 'I'hat parts of the second ancl the third chromosome vrhich are more effective in producing sterility in A/B hybrids are loce,ted in the regions i.nvol vi.ng interracial inversions. -134- Bateson, W. end ,R.. C. Punnet, (1905) Reportf.i to the Evolution Cornmi tte of the Royal Society London II. Bates6n, W. and E. C. Pmmet, (1911) On gametic series involving redup.:: lication of certe :i.l! te:cms • ,Jour • Genet. l: 2KS-302. Bridges, C. B., (1923) The translocat:Lon 0£' a. section of chromosome II upon chromosor11e III in Drosophile.. J\nut. Bee. 24: 4 2.6-427 • • • • • • • • • • • • • • • (U332) Appan~tus end methods for Droso1Jhile culture. The. Amer. Nat. 66: 250-273. (1935) Salivar~r chromosome ma.ps. Jour. Heredity 26: 60-6't. &nd T. H. T:Torgrn, (19?3) The thiTd chromor:::orne me~) of Publ. 327: 1-251. Burkcirt, .f.i., (1931) Investigac:i.ons genetic.us sobre una nuev<:1. rnntacion de Drosophil<: melr:,.nogastei.' deteruimmte de exce11c:i.ones herec1j_-t-,1:ir:hcs. 1• Crevr, F. Ji. E. and R. Lamy, (F''.32.) J\ cuse of conditioned ClorHirn:mce in Drosophils obscura. cTolir. Genet. 26: 251-258. Crew, F. A. F. :::nd n. Lamy, (1934) The second linka.c.;e grou.p :i.n Drosopbil<>c ~)seudoobscure.• Jour. Genet. 29: 267-276. Grev, F. A. F. and R. Lamy, (1935) Lirilrnge groups in Drosovhile GJS8uclo.= obscura, vrith notes on homology c:.nd the rn1turr0 of genie <::ction. Jour. Genet. 30: 15-29. Dobz.l:'w.nsky, Th., (1929a) GeneticDl 2.nd cytological proof of tnmslocations involving the third mid fourth chrornosomN:: of DroGopliila rnel2i:1 0-· g;:rnter. Biol. ZentrF.bl. 49: 408-419. -135- Dob:-'.hcnsky, Th., (1929b) A homozygous tr;Jnslocation in Drosophil~'. rnel<.mo- gaster. Proc. Nat. Acad, Sci. 15: 633-638. (Hl30a) Translocat:Lons involving the third nnd fmn·th chromosomes of D. rr.elenoga.ster. Genetic;.~ 15: 34 7-399. (19501:i) Cytological m::•.p of the second cb.rornosome of D. iri.eleo.nogaster. Biol. ZentreTb. 50: 671-685. (193lc;) Trnnslocations involving the second and the fourth chromosqnies of D. melc:.nogaste:c. Genetics 16: 6?.9-658. (H~Blb) The decreFse of crosE:ing-ovcr observecl. in trnns- locations Hnd its probable exple.nation'! The timer. Na.t. G5: ?14-2:30. (1932a) The bio1.roid mutation fr, Drosophil1?. mel;:mogoster. Genet~ cs •. 17: 069-392. (J93~?b) C;.rtological mc:.p of the X-chromosorne of Droso1 1bil2. (1932c) .StncUes on ch:comoEJome conjug.s.tion. I. Trc::nslocations ::i.nvolvi11t; the Sr" cond 1mcl the Y-·chromosorne of Drof>o:;:-Jhila me1211og2.ster. Z. I. A. V. 60: 255-286. (19320.) Del8tion of e section of the X-chrorr.or-clome of DrorJOfJhile me12.noggster. Bull. Labor. Geneticn, Lenin,srod 9: 193-216. (1955c:·) On the ::;teriJ:i.ty of the hrte1-rncfrl ]Jy1::iricl~~ in Drosophilc:, )Seucoob2curn. Proc. Nat. I!c1x1. Sci. 19: 397.J405. (193Zib) Role o:f:' the autoGrnPefi in the Drosophile i)seudoobsc1JT8. hybrids. Proc. Nat. /\c2d. ,Sci. 19: 950-953. -~ ... ( -1 9'.Z:l'L) 0 t1·1,:i l0 8'' ~J ,.. l.L · ,_) OI1 lo,,·ln'·i ---u __ .:.... c1,_ 0 s·J.l; rc>r-il ,_ - - - l t,v tJ e 1. r I. Spermatogenesis -156- Dobzho:nsky,Th., (HlE\5a) The Y chromosome of Drosophih:. pseudoobscurr::t. Genetics 20: 566-376. (1955b) Drosophih mirc1nda, a. nev• sr)ecies. Genetics ?O: 377-?J91. races of Dro:::10pbilr. pseudoobscura. ,Tour. Ex:~). Zool. 71: 4L19-L1J34. sterility factors :Ln Drosophile :pseudoolx'.CllTn. hybrid2,, Genetics 21: 110-135. Dor>zhr·nsky, Th., Eind H. D. Boche, (1933) Inter-sterile races of DrosophilE. pseudoobscurn Fro:: • Biol. Zentuilbl. 5~1: 314-330. Dobzhcinsky, Th. and C. C. Tc:m, (193621) .A compr:rntive stlidy of the chromosome structure in two reJE. tecJ species, Drosophila. pseudoohscl1r;,J end Drosophil&. mir~indc;_. The Amer. NB.t. 70: 47-48. Dobzlwrn:3lry, Th. oncl C. C. TBn, (1936b) StudieG on hybrid sterility III. l\ compfir:Lson of the gene re8rrc:1ngernent in tv.o s~iecies, Drosophilo ~;f:leudoobscurn and Drosophilc. miranda. In press, Z. I. -~. V. Emerson, li. J;., G. ':'. Beadle, ancJ A. C. Fraser, (1955) A srnnrnary of linkage studies in mD.ize. Cornell Univ • .Agricult. :Cxr'. Stat. 1nemoir 180. FroloFa, S. L. Bnd B. L. flstc:111row, (192D) Die Chromosomengm:nitur als systema.ti~::ches Merkmal. Zeit. f. ZellfoT.sch. rnikrosk. I1md:,. 10: 201-2.13. Heitz, E. and R. Bauer, (1933) Bevreise fur die Chromor~omennntnr cler Kernschleifen in den Kmmelker;1.en von Bibio hortulr:mus. 7ceit. f. ~ellforsch . . ikrosk. Annt. 17: 67-82. Kerkis, J1, (1956) Chromosome con,juga.tion lL h:rbrjos be~.~'.;'een Drosophil2. mel1.:.nogo.ster end Droso:ch:Lle sirrru.lc.ns. The Jilner. Nat. 70: 81-86. -157- Koller, P. C., (1932a) The rel2.tion of fertiJity factors to crossing over ir1 tb.e Drosophilo. o1)SClLr0. h:Y-bri.d. Z. I. A. V. 60: 137-151. ,(1932b) "Pointed-" mK1 the co11stitution of X-chromor.-wrne in DrosophilB. obscura. Jour. Genet. 26: 2:}.5-229. Ill • • • • • • · • • • "' e e (F136) Structure hybr:LcHty in Drosopbilc. :pseudoobscv.re.• J our. Genet. 3;~: 79-102. Kossikov ,R. V. and H. J. Huller, (1935) InvEJ.lide.tion of the genetic evidence for branched chromonemci.s. ,Tour. Heredity 26: 305-317. Lancefield, D. E., (l~llS:1) Two sex-linked let}~1als of simultaneous c:1v_,Jec-nmee in. DroE\ophile oliscura. Soc. E:xri. Bio. l'ffecl. 17: 56-77. •<ll•••••••e•dl111••e• (192?) Linkage relet.ions of the sex-linked chenwter in Drosophile. obscura. Genetics 7: 335-384. (192.9) A genetic study of crosses of hro ri::.ces or physiological species of Drosophila obscura. z. I. A. V. 52: 287-317. Mc:ckensen, O., (1935) LocotJ.Eg genes on S8.live:1ry chromOE\omes. Jour. Heredity. 26: 16~-174. l\lf'etz, C. 1!''., (1916) Mutations hi three species of Drosophil8. Genetics l: 5£-Jl-607. Morgon, T. H., (19lla) Im ci.ttempt to BJ'.lJ,.lyze the constitution of the chromosomes . on: the basis pf sex..,Jiioi ted inheri to.nee in Droso~Jhile. Jour. EY:p. Zool. 11: 365-413. (l~Jllb) Randon segregation vs. -coupling in Mendelian inheri tt:ince. Science 54: 384. of Morgen, T. H. and C. B. Bridges, (HH9) The constructi(in chror:1or~ome mar. Proc. Y,f,:j,J//i/..¢.J/:j,y{f-J Soc. Exp. Biol. Med. 26: 96-97. -138- Morgan, T. H., C. B. Bridges, and A.H. Sturtevant, (1925) The genetics of Drofiophila. Bibliogr. Genetica 2: 1-262. Muller, H.J., '(l~ll6) The mechcinism of crossing over. The .Amer. Nat. 50: 193-221. (1928a) The problem of genie modifictition. z. I. A. V. ,Suppl. 1: 234-260. (E:28b) The production of mubtions by X-rnys. Proc. Nat. Sci. 1rrash. 14: 714,--726 •. (H-150) Types of visible vu.rietions induced by X-rays in Drosophila. Jour. Genet. 22: 299-334. Muller, H. J. end E. Ji.ltenburg, (1928) Chromosome transloc::i.tions nroduced by X-r2ys in Dror-ioiJhila. l\nAt. Rec. 61: 100. Muller, H.J. and E. Altenburg, (1950) The frecyency of translocci.tions prochJceo by X-rays in Drosophila~ Genetics 15: 285-511. Muller, H. cT. and T. S. Painter, (Hl29) The cytological 8XIll'ession of changes JL gene aligme:nt produced by X-n::ys in Droso:pbila. The l\ni er. Nat. 63: 1~13-200. I!luller, H. <T. and T. S. Painter, (1932) The dif'fereatiation of the S8X chromosornes of Drosophila. into genetically active and ir ert 1 regions. Z. I. A. V. 62: 316-365. l'JfcClintock, Bl, (1930) A cytological demonstrEition of the loco.tion of an interchange between tvro non-homologous chrornoso.:.es o:f 7.ea me.ye.• Proc. (1901) C;ytologic[:l obriervetio:ns of deficiencies involvi11g knoPn genes' trnnslocE1.tior1s .s.nd .sn inversion in Zea me.ys. l\gric. Exp. Stc::t. Hes. Bull. 165: 1-30. r~issou:ci -139- Nobours, R. K. 8nd r'. 11. B. T\oberti:wn, (1933) f\n X-rEJ.y :tnoucec1. chromosomal tr;~nslo9e:1.tion in Apotettix eurycepbalus Hai1cl.J.ck. Proc.. lfat. f\c8.cl. Sci. Fash. l\'.': 254-239. Oliver, C. P., (H131) Chromosome aberraticms r:nd X6rc:1.y do::w.ge. J\nPt. Rec. 51: 100. (1932) An c-mnlysis of the effect of veryhig the o.uration of X-rEJ.y trentment ur1on the frec~uene~r of m1_-l~cd~ions. Z. I. f,. V. Gl: 4.-:l7-488. P8inter, 11 • S., (1931) A cytologiclil map of the X-chrornosome in Drosor)hil:3. melanogB.ster. _Arn:it. Rec. 51: 111. (19;53) A new· method for the study of chromosome ret?.rrangPrnent B.nd the plotting of chromosome maps. Science 78: 585-586. (1934a) _A mei:1 mil:lthod for the studv of chrornosome Ecberu .... rB.tions and the lotting of chromosome maps in Drosophila melano- Genetics 19: 175-188. (1954b) The morphology of the X-chromosome in sa1iv2.ry of Drosor)hilG. mel1:~.nog2.ster m2.p for this element. Genetics 19: 811(1 a nev tyi~e of chromosome 1 448~469. (1935) The morphology of the thircl chromosome in the salivary gla1d of Drosophili::_ melanogB.ster Bnd 8 new cytological rna.p lbf this element. Geneticr:i 20: 301-326. Painter, T. S., and H. J. IV!uller, (HJ29) Parallel cyt,ology and genetics of induced tro.nslocBtions 2.nd deletions in Drosophil8.• Jour. Heredity 20: 287-298. Pat::m, K., (1935) Cb.romosomenmorphologie bei Drosophil2. melBnog~i_ster und Drosophil8. simul2.ns unc1 ihre genetiscbe Bedeutung. Naturvriss. :?3: 557-543. -140- Patterson, J. T., V'. Stone, S. Bedichek, and M. Suche, (1934) The production of trcinslocat:l.ons in Drosophila.. The .M11er. Nat. 68: 359-569. Plough, n. H., (1917) The effects of temperr::.t.vre on cross.ing over. Jour. F.xp. Zool. 31: 445-~73. Poulson, D. F., ( 1954,) Tir: e of develor:ment of the two racei:: of Drosophile 1 pseudoobscura. Jorn~. Ex1). 7iool. 68: 237-245. Shopiro, H., (1932) The rate of ovi;:)Ofd_tion in the fruit fly, Drosophile. Biol. Bull. 63: 456-471. .Stern, C., (19~~6) E:tne neue chromot::omen Abe1--ration von Drosophi10 melanogaster lmd ihre Bedeutlmg fur die Theorie der line.s.ren Anordneu11g der Gene. Biol. Zentrci.bl. 46: 505-508 (192~l) Untm:suchlmgen uber Aberrationen des Y-dtr-nmosome von DrosophilD. mel[·,nogusteT. Z. I. A. V. 51: 2.53-35?-i. 0 ,1·-•nt ~t11--1rt,.._, c·.--..;' '1- A e 17: I'~lT • ' (lrlJ <.<;) The 1J !'8'='"T "I'ro:on°·e1·.-n--t ._ _,_, -· .•v, c.', 6 !l~--:;.t l 0 J. ___ .L (.I. J o-C• siv· "R" li-1lrp,c" l. 1.J .....l~.--.·--1 .c'- _, t 1• ----io.. f'-:octorc ... w _ c·,.,, in Drosophila, as sbmm by their mode of afJSociation. ,Tour. Exp. Zool. 14: 43-5 9. •••~•••1t•11••ees& (1915) The bok1.vior of the chromosomer3 e.s studiPd throl1gh linka.ge. Z. I. A. V. 13: 234-287. (1919) Inherited linlwge vrrfrtions in the second ehromosorne. Carn. Inst. V'ash. Publ. 278: 305-341. oe••••1J•e•ci••••• (1921) The North i r11eric1m spedes of Drosophi1B. 1 melanoge.st.er. Carn. InEJt. of 1'.'ash. Publ. No. 061. (19:?.9) The genetics of Drosophila sirnulr-ns. Carn. Inst. 1.'1ash. Publ. 399: 1-62. Sturteve.nt, A. H. end T. Dob~\h::msky, (1950) 11.eciprocal tr[u-1sloc;:;1tions in DrosophilB e.nd their bearing on Oelhothera pf~"'}'f-¢.Y... cytology a.nd genetics. Proc. Nat. Acad. Sci. ~ash. 16: 533-536. -141- Sturtevont, .A.H., 2nd C. n. Plunkett, (19~;6) Sec:nence of corre;,:pondi:"g third chromosome genes in Drosophilc:i. P1.el!,:.nog2.::;ter a.ncl Drosophila si.rrmlo11f3. · Biol. Bull. 50: Serebrovsky, P. 8., N. >;) I • 56~60. Dubin:i.n, I. P. ilgol, "'. N. Sliepkoff, and w. E'.. l\ltshuleT, (1928) The origin of mutotions througb the influence of X-ra.ys in D1~osophilc, rnelc-nor;c.::tcr. ,Tour. Exil. Biol • .(Hussiim) 4: 161-180. Tan, C. C., (1935a) Identificcction of the saliv<:>.ry glo.nd chromosomes in Drosophila I'se1Jc1oobscura. l::'roc. Eat. J~cad. Sci. Wash. 21: 200-202. (1935b) ,So.li vary gl8nc1 chromosomes in the two races of Drosophile. ;:Jse.udoobscm:a. Genetics 20: 392-402. Feircstein, }'\., (1928) 'rhe produetiori of r1u-tc.tions :::·nd rP-2:r:c~mgements of geneE: by X-rrws. Science 67: ';.,76-377. Fi.gure 1.-- From a la.rv.:1. het ro'.Cygons for transloca.tion Y-II A 0 w 2 i·.-,"\~4.9 ~ 3 .{;,"! . ., - ~ 4' . ·" Figures 2 and 5 .-- From two cells of a larva heterozygol1S for translocation Y-II B Figures 4 and 5 .-- From two different larva.e heterozygous for trnnslocation Y-II I Figure 6 .-- From a larva heterozygous for translocs.tion Y-II C Figures 7 and 8.-- From a single cell of a larva heterozygous for translocation Y-II C 9 -~ " I II Figure 9.-- From a larva heterozygous for translocation Y-III A Figures 10 and 11.-= From two se;·,arate cells of a larva heterozygous for tran,slocation Y-III B 12 Figure 12 . - From a larva. heterozygous for trensloce.t:i.on Y-IV A Figure 13 .-~ From a larva heterozygous for transloco.tion Y-IV B .. \ ' -~ 15 ~~~ ~-~' ~-~ -~ Figures 14 and 15 .-- From two separate· cells of e. larva heterozygous for translocation Y-IV C = = 17 Figures 16-18.-- FTom larvBe heterozygous for translocation Y-IV E Figures 19 and 20.-- From tv10 sepa.rate larvB.e heterozygous for translocation Y-IV J~ w :"'~: - 60 59 -- ~, 21 Figure 21.-- From a larva heterozygous for translocation II-III C {~. 'C/ 28 Figure 28.-- From a larva hirperploid for II_III B translocation and heterozygous for II::V part. Figure 29.-- From a larva heterozygous for II-III-(V) translocation, showing exchanges between II and V chromosomes. 31 30 Figure 30.-- From a larva heterozygous for translocation III-IV A Figure 31.-- From a larva hyperploid for translocation III-IV A and heterozygous for 1 Arrovrhead 1 inversion. . 1 l 32 Figure 52.-- From a larva heterozygous for translocation Y-III-IV At. Figure 33.-- From a larva heterozygous for translocation Y-III-IV B• .. ··~ 34 Figllre 34.-- From a larva hyperploid for translocation Y-III-IV B, showing a triplicate piece of the fourth chromosome attached to the Y-chromosome at chromocenter. JI' JV' /~Ill Figure 35 .-- From a larva heterozygous for transloca.tion II-III-IV .A. 11' im 111 II",' W' 36 IV" Figure 36 .-- An outline sketch drrnn1 from a larva heterozygous for trB.nslocation Y-II-III-IV A. 37 FiglJ_re '37 ,-- From a larva heterozygous fur translocation Y-II-III-IV-V A.: 39 38 'Figures 38 and 39 .-- From larvae of A/B hybrids, showing interracial inversion in th~ second chromosome. t 40' 1, \ >''. 41 Figures 40 ~md 41.--· P~:·1)1· larvt:1.e 0f A/n .:-,:,:•:.1-ic'.t3 Gii0·{:Li1e; interracial inversion in the third chromosome. r·· . l I,.,,, t·'" I,.... H ...,:.NA 4J • 4J 44 4445 4748 ' 52[53 :Sm bi 43.6 -Jss ~ ~ or cqm:u1rn: &4«> !;,, • I,.,,, 5&59 . ':h,w oos1 51 62 II i;;e ' j i . 74.9 929 ][ J: . ~ r5 r-~ri:~: - - ~-::A 1 :,:: IT ! 1 lll]~RI 0'. m '1 -"yll;fl .. Tf1r · , · tmrrniilt :~:ll LliO[l[ff\]J ;,,Je-i; !. · :,,_.,, l I -~ 1 r r;:l~~O ... . ····1 -. ~· ~'34 . . ·rr-rr·n:1[]], _LI J!Ji14rrfllr7·Ji 73b4 7~75 11; 76~ T,l1s .Jg 19);~- ~ail . \ ir u9 . 1 0 4 68.4 co67 ~ lm1:r _ 53.7 -~- ~)-(('._!~ JuL1 .JrJli~_:r_n:n:..11 ~ 1tL ~ "Jco I _I 1"-"'"" . ~~ 0 ,... :I~'-;.,,_ ~·~"A=~'""'"-~, n [ . I"_,,,. 1rl~:n::ffi/l:!lf'l1'1illlll/\ !!'Ill ~;·p_J :rrnrnJff:llill llrnfii'JUTCJlill'.illIOLl[[}/U_if]~l'lli mJTliff r1r1m:1 ULi!JJ ,Ill .i 4~46 ~47 ~49 4~bo 50;.1~~ ~ $ s~; 55~ ;,Js1 llU ;[l:ll/nlJP/illl: ID 87188 . ~9 8*° gcj91 91, 9 J 9~ 95 95/gs 9$97 ~ ,,, ~' ~ fil • ('.<Ro 6t2092 Figure 42.-II- A cytological map of euch_romati.c area of the second chromcsome showine; the typical morphology as this appears in.salivary glands. III- A cytologica.l map of euch-f'omatic area of the third chromosome showing the t;y-pical morphology as this appears in salivary glands·. rV- A cytologica.l m2,p of euchromatic a.Tea of the fourth chromosome showing the typical morphology as this appears in salivary glands. The crossover saale of genetic map is shown below each ch..romosome and translocation breakage points are marked by the lines above thetbhrornosomes. The dotted lines above the chromosomes represent lirnits of excisions. The solid lines above the chromosomes represent limits of inversions.