University of Southern California Dissertations and Theses

Cytological and genetical study of certain regions of the chromosomes in Drosophila pseudoobscura

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Cytological and genetical study of certain regions of the chromosomes in <italic>Drosophila pseudoobscura</italic>

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Content CYTOLOGICAL AND GENETICAL STUDY OF CERTAIN REGIONS OF THE CHROMOSOMES IN DROSOPHILA PSEUDOOBSCURA RACE B A Thesis Presented to the Faculty of the Department of Zoology University of Southern California In Partial Fulfillment of the Requirements for the Degree Master of Arts by David Niemetz June 1937 UMI Number: EP67108 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Disasrtaîien AWMisMng UMI EP67108 Published by ProQuest LLO (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLO. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLO. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346 This thesis, w ritten by ............. under the direction of h Faculty Committee, and approved by a ll its members, has been presented to and accepted by the C ouncil on Graduate Study and Research in p a rtia l fu lfill ment of the requirements fo r the degree of MASTER OF ARTS D ean Secretary D ate Juna.,.-L9.o.?... F acu lty C om m ittee C hairm an FOREWORD The necessity for linking genetical and cytologi- cal data was known for several years, but it was not until 1934, when Painter developed his technique of staining the salivary gland chromosomes of Drosophila larvae, that this was possible to a great extent* This paper reports linkage data for the new mutants, white and vermilion, and gives a preliminary cytological study of the salivary gland chromosomes of the Notch mutants. TABLE OF CONTENTS CHAPTER PAGE I. REVIEW OF THE LITERATURE AND STATEMENT OF THE 'PROBLEM............................... 1 Comparison of Race A and B .............. 1 Deficiencies ........................... 3 Structure of the salivary chromosomes . . 7 Cataloguing of the salivary chromosomes . 9 Problem......................... 11 II. MATERIALS AND METHODS ...................... 12 Genetical......... * . 12 Cytological........................... 12 Examination of the salivary gland chromosomes......................... 16 III. LINKAGE RELATIONS OF CERTAIN MUTANTS ON THE X-CHROMOSOME................. . 19 White / singed bubble experiment ..... 19 White / singed bubble vermilion experiment........................... 21 Beaded vermilion / white singed bubble experiment............................ 23 Linkage relation of Notch, white and vermilion............................ 23 Construction of the genetic m a p ......... 25 Comparison of the genetic maps of certain regions of the X-chromosome in Race A and B ................. .. 30 CHAPTER PAGE IV, CYTOLOGICAL STUDY OF CERTAIN REGIONS OF THE CHROMOSOMES OF RACE B ................ 32 Inversions ..... ................ 34 Non-pairing between homologous chromosomes ............. 38 V. SUMMARY.............................. 46 BIBLIOGRAPHY ..................................... 47 LIST OF TABLES TABLE PAGE I. THREE POINT GROSS....................... . 20 II. FOUR POINT CROSS...................... 22 III, FIVE POINT. CROSS .......... 84 IV. CONSTRUCTION OF A GENETIC MAP OF CERTAIN REGIONS OF THE X-CHROMOSOME OF RACE B . . . 26 V. COMPARISON OF PERCENTAGES OF RECOMBINATION BETWEEN SINGED AND BUBBLE............ 27 VI. COMPARISON OF AVERAGE MAP DISTANCES OF RACE A WITH RACE B ........... 29 LIST OF PLATES PLATE I. MALE AND FEMALE LARVAE OF DROSOPHILA PSEUDOOBSCURA........................ II. CHARACTERISTIC PORTIONS OF THE CHROMOSOMES III. CONFIGURATION OF AN INVERSION ........ IV. CONFIGURATION OF AN INVERSION ......... V. PORTION OF RIGHT LIMB OF X-CHROMOSOME . . , VI. PORTION OF RIGHT LIMB OF X-CHROMOSOME , , , VII. MIDDLE PORTION OF III CHROMOSOME .... VIII. PROXIMAL PORTION OF IV CHROMOSOME . . . . IX. DISTAL PORTION OF III CHROMOSOME .... , X. PART OF UNIDENTIFIED CHROMOSOME . . . . PAGE 13a 33 36 37 40 41 42 43 44 45 CHAPTER I REVIEW OF THE LITERATURE AND STATEMENT OF THE PROBLEM COMPARISON OF RACE A MID B Laneefield (1925) differentiated Drosophila pseudoobscura into two races or physiological species that were called races A and B which when crossed produced ster ile hybrid males. They are similar in appearance, but differ visibly in the shape of their Y-chromosomes (Lance- field 1929, Dobzhansky and Boche 1933, Roller 1934) and in their physiological characteristics (Poulson 1934). Of the six types of Y-chromosomes in Drosophila pseudoobscura, three are present in race A, and three in race B. One of these,jcharacteristic for race A, a long J-shaped chromosome, is found in western British Columbia, western Washington, Oregon, and California. The second, a short J-shaped chromosome, is found in race A strains coming from eastern British Columbia, eastern Washington, Idaho, Montana, Colorado, Texas and Utah. The third, a very short V, is found only in one strain from Cedar City, Utah, This is identical with the short V chromosome of race B, which is found on Vancouver Island and in the region around Puget Sound. The second type in race B is a very pronounced unequal armed V, which is found in southern Sierra Nevada and in the Coast Range of Southern California; the third, a long, moderately unequal armed V, is found in all other localities where race B abounds. (Dobzhansky 1935). Tan (1935) discovered from cytological study that the hybrid of races A and B possessed salivary chromosomes v/ith six invert ed sections. Further investigation of Dobzhansky and Tan (1936) revealed that there is one inversion in each limb of the X-chromosome. In the left limb there are two additional sections that frequently fail to pair, although the arrange ment of the discs is identical in both races. There is one inversion in the second chromosome and one in the third but the gene arrangement is identical in the 4th and 5th chromo some of both races. Lancefield (1929) and Roller (l932a) found in fe male hybrids resulting from the crossing of race A and B that a suppression of crossing over occurs at both ends of the X-chromosome while in the middle crossing over is almost normal. This suppression of crossing over is due to invert ed sections of the X-chromosome (Sturtevant 1926). Rearrange ment of the genes within the chromosome takes place during the process that leads to the differentiation of these races. Whether or not the variations in the gene arrangement are causialiy related to the hybrid sterility in Drosophila pseudoobscura, nevertheless, it remains a fact that racial differentiation partook in this case of both sources of evolutionary variability - gene variability and variability in the gross structure of chromosomes (Tan 1935). Tan states further "that the hybrid sterility may be in some 3 cases directly caused by structural differences in the chromosomes of the parental species, especially in the hy brids that produce fertile allotetraploids," Dobzhansky (1933) found that the sterility of these AB hybrids is due to an interaction of complemental factors rather than to differences in the gross structure of the chromosome. DEFICIENCIES Mutants that are due to losses from the gene string are known as deficiencies. The first Notch mutation, a deficiency, was discovered in 1914 by Dexter in Drosophila melanogaster and he showed that the character was sex-linked, dominant in the female, and lethal in the male. Bridges, in 1915, found a second "Notch," and located it at 1.5 units to the right of the white locus (Morgan and Bridges 1916). Several other Notches were found by Morgan, Bridges, Muller and Gowen. A new characteristic was found in Notch-6 which showed a "pseudo-dominance for facet" (Metz and Bridges 1917), When a Notch-6 female was crossed to facet males, all of the Notch-6 daughters were at the same time, facet. This simi larity to the behavior of the forked in f-B deficiency (Bridges 1917) and the vermillion in V-deficiency (Bridges 1919) suggested that Notch was a deficiency that included the locus for the facet character. Notch-8, found by Mohr in 1918, involved a longer section than the previous Notches and gave pseudo-dominance and exaggeration with facet, with 4 white and its eleven allelomorphs, and with Abnormal (Mohr 1919). Mohr states that recessive genes in the region which is homologous to the deficient region manifest them selves in the adult fly. Of twenty-five Notches, four - 18, N9, N18, N21 - have been shown to be extreme enough to cover the locus of white. In Drosophila pseudoobscura. Notch of race A is not a deficiency for the white eosin or yellow locus (Lancefield 1922). In race B neither 11 or 12 is a deficiency for the white eosin locus of race A, the singed of race B (Beers unpub.), or w^hite of race B (String 1936) . The theory that certain mutants are due to losses from the gene string, a deficiency, has been shown on the basis of genetic data. Painter (1954a) developed a new technique of staining salivary gland cliromosomes of the lar vae of Drosophila which confirmed the early theory of defi ciencies. The work that has recently been done on defi ciencies, notably the Notches in Drosophila melanogaster, has been accomplished through salivary analysis, by Painter, Mac- kensen, Muller, Prokobyeva, Demerec, Bridges and many others. All of the dominants, especially those which are lethal when homozygous, require checking for chromosomal rearrange ments, such as deficiencies, duplications, translocations, and inversions. The correlation between genetic maps and parti cular chromosome localities is an important feature of this work (Bridges 1936). 5 One of the latest reports of a mutant due to a defi ciency was confirmed by Li who observed a "Buckle" and loop at about section 45 (Bridges, Li and Skoog 1936), This is in the right limb of the second chromosome. For more exact study, numerous permanent preparations of salivary chromo somes of Notopleural/ore-R females of Drosophila melanogas ter were made. The normal map shows fifty distinguishable transverse elements between the breaks of the Notopleural deficiencies - 44F-45E, "Repeats" offer a generalized, and perhaps the most frequent, mechanism for further steps in rearrangement - either translocations, inversions, or deficinecies - through a preliminary synapsis of homologous or allelic bands or sections, which are carried in separate chromosomes or local ities, with subsequent crossing over to give the new rear rangements. When a normal and deficient X-chromosome unite in somatic synapsis they pair up line for line, except in the deficient regions where the normal chromosome buckles. (Bridges, Li and Skoog 1936). This enables one to deter mine in the most detailed way how much is missing morphologi cally from the deficient element. It is found that genetic deficiencies also amy be accompanied by the loss of definite bands and areas in the X-chromosome. In example, according to Mackensen, is in the stock known as "Notch 8," of Droso phila melanogaster, which shows genetically the absence of 6 white, facet, and abnormal abdominal sclerites. Certain bands of the "facet area" are always characteristically ab sent. This study proves definitely that genetic deficien cies may also be accompanied by cytological deficiencies and it enables one to determine the cytological locus of genes more exactly than the old translocation method (Mackensen 1954). The determination of the extent of a deficiency is a matter of importance. By the extent is meant the num ber of units that are included in the affected section. Genetic tests of breeding show that in the majority of cases only a single known mutant locus is deficient. The defi ciency acts as a sex-linked recessive lethal, and prevents the development of a male zygote which inherits the affect ed chromosome. In the female all such deficiencies when present appear pseudo-dominant (Patterson 1954). Patterson also showed that the loss of an entire chromosome, or half, or a still smaller but definitely measurable section produce the deficiency phenomena. Demerec and Margaret E. Hoover (1936) demonstrated salivary chromosome figures of a two banded deficiency and a deficiency including this one plus the absence of addition al bands. Bridges (1936) has also demonstrated a fifty band deficiency. STRUCTURE OF THE SALIVARY CHROMOSOMES Painter (1934a) realized the value of the enor mously enlarged cells and chromosomes in the salivary glands of Drosophila larvae and he developed the Aceto- carmine technique of staining them. This was a most signi ficant step in the study of chromosomes. The enlarged chromosomes can be explained according to Bridges (1935) by the fact that they probably have divided within themselves many times so as to become enlarged and at the present date they are thought of as composite structures made up of many genes which are lined up in the chromosome with a definite continuity and pattern. A gene is associated with a chromosome in a causal manner for the production and develop ment of certain characteristics of an organism. Up to the present it is not known exactly what a gene is, but it is generally considered to be the determiner of certain char acteristic. The gene ^ s action is thought to be the result of complex bio-chemical reactions within the organism. The chromosome group of Drosophila pseudoobscura, as seen in spermatogonial, oogonial, or nerve cells, consists of five pairs of chromosomes: a V-shaped sex linked chromo some, known as the X-chromosome, three rod shaped autosomes, and one very small dot-like autosome. In the salivary glands of the adult larvae five long strands, each with the proximal end embedded in the chromocenter, are found. They represent the right limb of the X-chromosome, the left limb 8 of the X-chromosome, the second, third and fourth chromo somes. The chromocenter is a chromatin coagulum. In favorable cases a very short (sixth) element may be seen attached to the chromocenter - this is the 5th pair of chromosomes. - Each strand represents two closely paired homologous chromosomes, the result of somatic syna.psis (Tan 1935). Chromosomes are made up of many fine transverse strands. Some of these strands appear as bands or vesi cles. All of these bands and vesicles cut a horizontal plane across the chromosome. Strands may be missing or un like those of the homologous chromosome and cases such as these are known as chromosomal abberations. The average length of moderately stretched chromo somes in Drosophila melanogaster is shown to compare with Drosophila pseudoobscura. Drosophila melanogaster Drosophila pseudoobscura (Bridges 1936) (Dobzhansky &^Tan 1936; measured from their drawings) X-chromosome. • . 220 XR ............ 270 II chromosome . . 460 XL ....... 185 III chromosome . • 485 2.••••.•• 310 IV chromosome • • 15 3 . . . . . . . 205 Total . . . 1180 micra 4 . . ..... 240 5 .............. ....8 Total . . • 1188 micra The total length of the moderately stretched salivary chromosome is approximately one hundred and fifty times that of the total length of the gonial chromosomes which are only seven and one-half micra. Individual salivary chromosomes with lengths exceeding one hundred and eighty have been measured. These stretched chromosomes or portions show most of the stretching in the hyaline zones between the dark bands. The heavier cross bands or capsules retain their shape as broad firm discs while the material between may stretch into a narrow cord ten times its normal length but still show its compound nature. Each of the fused mat ernal and paternal homologous cliromosomes consists of eight chroffionemata or gene strings which are derived from the cor responding chromosomes by successive divisions without com plete separation of the division products. The cable of eight plus eight strands shows its structure most clearly in the less heavy cross-bands in which sixteen individual dots, vesicles or small capsular units may be seen. (Bridges 1955) Chromosomes appear under the microscope in many kinds of coils, twists, switchbacks, and other complicated groups. Many times it is difficult to study the banding due to these complications and a specific knowledge of the char acteristic endings of the chromosomes is valuable. CATALOGUING OF THE SALIVARY CHROMOSOMES It has been shown that the enormously enlarged 10 chromosomes present in the nuclei of salivary gland cells are to be regarded as normal chromosomes rich in constant structure and it has been demonstrated that the series of structures observable along the length of such chromosomes can be correlated with the series of genic loci on the link age maps. For such analysis two types of chromosome, maps are needed: first, linkage maps which give the sequence and location of genes for all mutant characters which may be in volved, and, second, accurate detailed charts of all the normal salivary chromosomes against which to check the points of breakage or area of disturbance. A necessary detail for a map of chromosome banding is a definite measurable system of referring to a particular band or section of a chromo some. Bridges (1935) devised a system for cataloguing the chromosomes of Drosophila melanogaster and Tan and Dobzhan sky (1936) followed his example and subdivided the chromo somes of pseudoobscura into 100 arbitrary sections, numbering them consecutively from the spindle fiber to the free end in each chromosome. The sections are numbered from 1-17 for the left limb of the X-chromosome, 18-42 for the right limb of the X-chromosome, 43-62 for the second chromosome, 63-81 for the third chromosome, 82-99 for the fourth chromosome, and the fifth was numbered 100. One can readily see that the number of a section is itself a key to the chromosome limb, and also to the relative position along that limb. Since sharpness and definiteness are essentials, each sec 11 tion begins with a conspicuous and easily recognized band. The division point is made just to the left of the chosen main band toward the proximal end. The individual bands are not given definite numbers because the numbers would have to be changed from year to year as knowledge of the banding becomes more detailed and small bands are seen which were previously missed. There are many recognizable landmarks on the chromo somes by which they may be identified. The free end of each chromosome limb presents a characteristically narrowed ter minal region. It is suggested by Bridges (1935) that this narrowed region represents a lag of one division in the gene- strings, somehow due to the terminal position occupied, but not due to special properties of those particular genes. Two thousand six hundred and fifty bands have been recorded in the Drosophila melanogaster salivary gland chromosomes. In Drosophila pseudoobscura 2,350 bands are recorded on the maps by Tan (1933) and Dobzhansky and Tan (1936). These bands were counted from drawings. It is probable that more will be found. PROBLEM This research of Drosophila pseudoobscura was divided into two parts: (l) The genetic study of beaded. Notch, white singed,’and vermilion. (s) The cytology of certain regions of the salivary chromosomes. CHAPTER II MATERIALS AND METHODS GENETICAL The files used in these experiments were taken from the stock cultures maintained at the University of Southern California genetic research laboratory. The standard cornmeal-molasses-agar-yeast medium in half-pint milk bottles was used (DIS No. 4). Virgin females were secured from bottles in which all the flies had emerged within a twenty-four hour period. Each pair mating was started in a vial and three or four days later was tranferred to a bottle. All records of matings and counts are on file in the laboratory at the University of Southern California. CYTOLOGICAL Aceto-carmine stain is the most effective to stain chromosomes for detailed structure. It is very penetrating and permeates deeply into the tissue that is being stained. The aceto-caimine stain which was used in the experi ments was made up as follows: glacial acetic acid diluted to 45 per cent was saturated with carmine number forty. This solution was then boiled under a reflux condenser for two IS hours. The solution was allowed to cool and then filtered. A clear dark red solution was obtained. (Marshak 1936). Large larvae were obtained from single pair mat ings transferred daily from one bottle to another to avoid crowding. The larvae were raised at a temperature of 19^ C. Fresh yeast was added to the food in the bottles on the sixth day when the larvae reached half of their growth. Only large adult larvae were chosen because if larvae are too young the salivary glands will not be sufficiently deve loped and if the larvae are in the first stages of pupation the salivary glands will have started to degenerate. From these large adult larvae only wide, long, bloated glands were used. Male larvae are distinguished from female larvae by their large transparent elliptical testes which are imbed ded in fat bodies that lie in the region of the fourth trach eal branch counting from the posterior end. The ovary is in the same region but is very much smaller and is round in shape. The males can easily be distinguished from the fe males when crawling in Ringer^s solution against a black background, because the large testes can be seen through the transparent body wall. In the female the ovaries usually cannot be seen due to their small size. (Plate I) Notch females were crossed to white males and the FI generation consisted of three types : (l) Notch females, (2) wild type females, and (3) wild type males. The Notch Tlate I ^ v \ V e v i o » ' a f v i r V c r i o v ’ moviVK hooK^ rf\a\pigh,\an tvôç,Vve a\ t ukes__ s ovavy_ i p o s ^ - e v i o ' f ^os-Ve.r»OY Ç ? * atv<i ^ \akvvae o9 O vosopK \\a ps^.odoohse.uv'a 14 females heterozygous for the white recessive were mated to white eyed males. The results of this cross were larvae of Notch females, white eyed females, and white eyed males. The larvae of Notch females were distinguished from the white eyed females by the malpighian tubules which are pale yellow in color. The white eyed females have a white color ation of the malpighian tubules. Only glands from Notch females were chosen for staining. The larvae were removed from the food with a nee dle and placed in a Syracuse dish with seventy-three hun dredths per cent sodium chloride which had been chilled to almost freezing, as recommended by Bridges. (Ringer’s solu tion was used also.) The dissection was made on a black background with transmitted light under a dissecting binocular (g.5x). A needle bent at the end was placed just behind the black mouth hooks which a,re easily seen at the anterior portion of the larva. The head is cut off by exerting pressure on the needle, and the viscera are disgorged from the body. The salivary glands are connected to two distinct fat bodies. The glands appear transparent.and bluish in color and resem ble two bunches of grapes connected to each other by a com mon duct which leads into the pharynx. The glands were separated by means of needles from the fat bodies and trans ferred by needle or pipette to near freezing aceto-carmine stain in a Syracuse dish. They were left in the stain for 15 10 to 20 minutes. Too short a staining period will lead to fragmentation and poor staining. The glands were now placed on an albuminized slide.^ The albumin coating pre vents the chromosomes from becoming crushed too severely and also makes them adhere to the slide more firmly. A cover slip was placed over the glands, the slide was put under a corner of a blotting towel and the excess stain blotted off. At the same time the cover slip was pressed down and the glands were slightly crushed. This partially freed the nuclei from the cells. Next the cover slip was held firmly in place and a blunt needle was drawn across the top of the cover slip which spread the chromosomes more fully. (Shultz 1936). Permanent slides were made from exceptionally fine slides by the following methods. Marshak’s method (1936) is to make a saturated solution of carmine and glycerine which is filtered and placed about the cover slip with a piece of absorbent paper placed against one edge of the cover slip. The glycero-carmine will replace the aceto-carmine under the cover slip over night. The excess glycerine may be removed Twenty-five grams of Merk’s powdered egg albumin, 100 cc. of water, and 0.5 grams of thymol were mixed thor oughly and allowed to stand for several days. The top por tion was decanted. A drop of the albumin is placed on a clean slide and another slide is used to spread it over the surface. The albuminized slide is allowed to dry. 16 with alcohol and the slider sealed with balsam or any suit able seal. Bridges method produced better results. In this case the slide is allowed to stand over night in a ninety-five per cent alcohol vapor jarThe filter paper around the slide will give off alcohol vapors which replace the aceto-carmine stain. The cover slip usually comes off, if not, the slide may be immersed in alcohol and the cover slip will detach itself. The slide is briefly drained (not dried). A drop of Euparal is placed upon the glands and a clean cover slip is immediately placed on top. The excess Euparal is removed by putting the slide under a blot ting towel and pressing gently. The slide is allowed to dry and is then ready for permanent use. (Bridges 1936). EXAMINATION OF THE SALIVARY GLAND CHROMOSOMES The arrangement of apparatus for the examination of the salivary chromosomes is as follows : a lOx ocular, nine millimeter 1.25 N.A. oil immersion objective, a Bausch- Loffib research lamp, wratten green filter number 61, and a camera lueida. The substage condenser was a 1.25 N.A. ^An alcohol vapor jar is made by placing strips of filter paper in the bottom and around the sides of a coplin staining jar. The jar is filled one inch deep with 95 per cent alcohol and the cover of the jar is sealed with vase line. 17 Oculars higher than lOx seem to yield inferior results. A binocular microscope was used for both examinations and drawings. All drawings were made from permanent prepara tions and enlarged to about 5,000 magnification. These were reduced by photographic means. Actual magnification of the chromosomes was ,970 times. The intensity of the light is regulated by a var iable resistance, of 175 ohms and 1.5 amperes capacity, in the primary 110 volt circuit to the transformer. This in creases the life of the lamp. The light from the ribbon filament is brought to a sharp focus in air as near as practical to the front of the condensing lens. This is accomplished by turning the loop of the filament toward the back in the housing and racking the condenser to its limit forward. The filament is carefully aligned with the center of the condenser. An iris diaphragm is mounted in the plane of the image of the filament. The iris diaphragm instead of being behind the water jacket is placed in front. To find the exact setting for the iris, place on the stage - condenser oiled - a slide and focus upon it with the oil im mersion objective. Next place the lamp with the field iris about 15 cm. from the mirror face and center the beam on the mirror. With open field iris focus the edges of the ribbon filament sharply in the field by racking the condenser screw. Now close down the iris to about 2 mm, and slide it along its trough until its edge is perfectly sharp in focus. In 18 critical use this field iris is closed to give a lighted area about half the diameter of the field of the objective and its edge should be clearly in focus in the plane of the prepara tion. The iris beneath the condenser should then be closed down until the light haze in the marginal field narrowsuntil it disappears by coinciding with the edge of the field iris image. This increases definition by contrast. The carmine stain absorbs a maximum of the green at about 530. Hence to get greatest contrast a green filter was used whose transmission was entirely within the absorption band of carmine. For general use Wratten number 61 is the best, since it allows discrimination of the relative intensi ties of the lines by having a broader transmission band than the absorptive band of carmine. Stretched places in the chromosomes yield best re sults in checking details of banding. The stretch comes al most exclusively between bands, and the bands are thus moved apart sufficiently to be distinctly resdvable into separate structures (Bridges 1936b). CHAPTER III LINKAGE RELATIONS OF CERTAIN MUTANTS ON THE X-CHROMOSOME Approximately four thousand male flies from thirty-six pair matings were counted to determine the recombination per centages of the two new mutants white and vermilion with bead ed, singed, and bubble. These mutants show the following characteristics : (l) The white and vermilion mutants are referable to the color of the eye and also the testis sheath. (S) Beaded appears as small scallops at the end and more often on the inside edge of the wing. (3) Singed is the condition of singed bristles on the head and thorax. (4) Bubble is the appearance of one or more bubbles in either one or both wings. These bubbles are filled with a colorless, odorless fluid. WHITE / SINGED BUBBLE EXPERIMENT On December 2, 1936, five virgin white-eyed females were mated to singed bubble males in single pair matings. The FI females were mated to their brothers which were all white males. Seven crosses did not survive due to mold. The offspring from thirteen single pair crosses were counted for twelve days. The result of these crosses is shown on Table I. TABLE I THREE POINT CROSS Male Count White / singed bubble Heterozygous'^ W+ + + sn bu Test cross cf S Non-crossovers w sn bu Single crossovers w sn bu w bu s Double crossovers wsn bu Total males 1,418 565 606 Recombination between w-sn 5 16 5 16 56 167 2 1 1418 Recombination Percentages 17.7 24 1. 1418 sn-bu 56 167 2 1 226 1418 w bu 56 167 5 16 244 1418 16. 17. w" "sn" bu 1.7 16 21 The Drosophila Information Service recommends that linkage data be summarized in the following form: ..... mutants involved; constitution of heterozygous female; date at which test-cross flies began to emerge; both complementary classes, conventionalized by putting first the class starting with the left most mutant; total (N); primary recombination per centage (El, R2, etc.); R1 percentage of recombina tion of characters of left-most and next to right of loci involved. Using the above form the results are: White x singed bubble; w + + / + sn bu; S7b9; 0=563 + 608, 1 = 5 t - 16, 2 = 56 + 167, 1,2 = 2 + 1; H =1418; R1 =1.7, R2 = 15.9. WHITE SINGED BUBBLE / VERMILION EXPERIMENT On February 20, 1937, a mass mating of ten vermilion females and three white singed bubble males was made. The FI females, on March 16, 1937, were mated to their vermilion brothers in fifteen single pair matings. Three more of these single pair matings were made on'March 21, 1937, and eight more on March 28. This totals twenty-six pairs. Eleven bottles were discarded due to non-mating, bacteria, or mold. The offspring from five pair matings were counted by Beers and ten were counted by the author (Table II). According to the Drosophila Information Service for mula, the results are: White singed bubble x vermilion;w sn + bu/ + + v +; 37cl6; 0= 505 + 897, 1 ^14 + - 13, 2=7 - v 7, 3 = 306 - v 38, 1,2 = 0 + 0, 1,3=0 + 5, 2,3 = 0 + 1, 1,2,3 = 0 + 0; N =1794; Rl= 1.8, R2 =0.9, R3 = 19.2. TABLE II FOUR POINT CROSS Male Count White singed bubble / vermilion Heterozygous ^ Wsn + bu + + V + Test cross S cT Non-crossovers w sn bu Single crossovers wv sn bu w sn V bu w sn V bu w bu sn Double crossovers w V bu sn w sg V bu Triple crossovers 563 606 14 13 7 7 306 38 0 0 0 5 1 1 0 1794 Total males 1,794 Recombination between: w-sn 14 13 __5 32 1794 sn-v 14 1. 16 1794 0.9^ v-bu 306 38 I # Recombination Percentages "sST b\i 1.8 0.9 19.1 23 B Ü B A D Ï G D TflORjWLrijlOlf // W r B O C T C E 8:[NG:ED BUlBBIjE j S a C I f E I l O I M O E J f n ? From the mass mating of.the white singed bubble / vermilion experiment eight of the FI wild females were also found to have the mutant character of beaded in a heterozygous condition as well as white, singed, vermilion, and bubble. Therefore when eight single pair matings of these flies were made (wild females and their vermilion brothers) there appear ed in the-F2-generation the character of beaded as well as the other mutants. The offspring from these eight single pair mat ings were counted for fifteen days (Table III). The results are summarized by the Drosophila Informa tion Service formula as follows: Beaded vermilion x white singed bubble; bd + + v + / + w sn + bu; 37c 16; 0-227 - + 150, 1 = 25 + 134, 2 -4+7, 3 =0+0, 4-6 + 94, 1,2 -0 + 0, 1,3 =0 + 0, 1,4 -47 + 4, 2,3 -0 f 0, 2,4-0 + 0, 3,4=1 + 1, 1,2,3=0 + 0, 1,2,4 — 0 + 0, 1,3,4=0 + 0, 2,3,4= 0 + 0, 1,2,3,4 =1 + 0; N 701; R1 30.2, R2 1.7, R3 0.4, R4 21.8. LINKAGE RELATION OF NOTCH, WHITE, AND VERMILION NOTCH / WHITE EXPERIMENT As the result of mating six pairs of white-eyed males with Notch females heterozygous for vfhite, no crossing over between Notch and white was obtained. A total of five hundred TABLE III FIVE POINT CROSS Male Count Beaded vermilion / white singed bubble Heterozygous ^ + wsn + bu bd + + V + Test cross cT cT Non-crossovers Total males 701 Recombination between: bdv w sn bu Single crossovers bd w sn bu V bd sn bu wv bd V bu w sn Double crossovers bd w sn V bu bd w sn V bu 4 crossovers bd w sn V bu 150 25 134 4 7 6 94 47 4 1 1 1 0 Recombination Percentages 54.19 bd-w 25 134 47 4 1 __1 212 701 w-sn 4 7 12 701 sn-v 1 1 1 __3 701 v-bu 6 94 47 44 1 1 __1 154 701 30.2# 1. 0.4# 21. 30.24 "w" 1.7 0.4 21.82 bu" eighty-eight females were counted and two hundred eighty-three males. In the parent cross of Notch females with white males, no Notch white females appeared in the FI generation indicat ing that the Notch deficiency is not extensive enough to cover the locus of white. NOTCH / VERMILION EXPERIMENT Ten pairs of Notch females and vermilion males were mated. The Notch females of the FI generation did not show the vermilion character. This proves that the Notch defi ciency does not cover the vermilion locus. CONSTRUCTION OF THE GENETIC MAP A genetic map (Table IV) was constructed by using the average percentage of recombination as tabulated in Tables I, II, and III. In these Tables the recombination percentages between white and singed were 1.7, 1.8, and 1.8. This yields an average of 1.7 for the percentage of recombination between white and singed. In the same manner an average of 18.7 per cent was obtained between singed and bubble. Recombination percentages between singed and bubble have been recorded pre viously. Table V was prepared to show the old records in comparison to the ones obtained as set forth in this paper. Although the average of 19.4 recorded from the three experi ments reported in this paper is high in comparison with the TABLE IV CONSTRUCTION OF A GENETIC MAP OF CERTAIN REGIONS OF THE X-CHROMOSOME OF RACE B TABLE I II III Average Genetic Recombination Percentages w 1.7 sn bu 16 w 1.8 sn V 0.9 19.8 bu b'd î 30.8 1 w 1.8 V 1 sn V 0.4 81.8 bu’ b*d 30.8 t w 1.8 sn V 0.7 18.7 bt -- 30.2 1 38 38.7 . 1 ' T - ... .....51,4 bd w sn V bu TABLE V COMPARISON OF PERCENTAGES OF RECOMBINATION BETWEEN SINGED AND BUBBLE Reporter LancefieId Beers Smith Finley- Average Recombination Percentage 17.0 18.6 16.19 go. 3 17.g 16.46 Sex Total no. 677 1871 F Cross bd sc se s / sn bu sc sn bu / se bd / sn bu Niemetz Average 16.0 20.1 22.2 19.4 1418 w / sn bu 1794 w sn bu / V 701 bd V / w sn bu 88 16.4 average of other workers, individual experiments check favorably except in the last. The first experiment resulted in a recombination per cent of 16. This coincides with the result of Smith who obtained 16.8. 80.1 recorded for the second experiment approaches the recombination per cent of 80.3 reported by Finley. In the last experiment only a few flies were raised which may account for the high percentage of 88.8. Recombination percentages between singed and bubble vary from 16 to 22.8. The second experiment is concerned also with vermilion and the third experiment includes both ver milion and beaded in addition to other mutants. The average recombination percentage between singed and vermilion was 0.7. Beaded, used in only one experiment, revealed a recombination percentage of 30.8 with white. Using these figure as a starting point, it was pos sible to formulate a genetic map placing the various mutant as follows: Beaded 0, white at 30.8, singed at 32, vermilion at 32.7, and bubble at 51.4. This is the first time in the history of race B that recombination percentages betv/een beaded — white, white — sing ed — vermilion, and vermilion — bubble have been obtained and these results recorded on a genetic map. Undoubtedly more new mutants will be discovered and with these discoveries a more complete and accurate map will be constructed. 30 COMPARISON OF THE GENETIC MAPS OF CERTAIN REGIONS OF THE X-CHROMOSOME IN RACE A AND B In race A the genetic map of the X-chromosome begins at 0 with the mutant. Pointed. Pointed has not appeared in race B as yet, so beaded, being the left most mutant, is given the value of 0. The other mutants are located according to their recombination percentages in a sequence to the right of beaded that is identical with the same mutants in race A. The distance between beaded and white in race B of 30.2 compares favorably to the 43.4 in race A, because more mutants are knovm to lie between beaded and white in Race A than in race B. These make it possible to detect more dou ble-crossing over in race A which increases the distance bet ween the two. The distances between white and singed in races A and B are nearly the same as is shown by the figures 1.2 and 1.8. The singed and vermilion recombination percent age in race B is 0.7 which is much lower than 2.6 in race A, Singed to bubble in race A is about 18.6 in comparison with 19.4 in race B. The distance between vermilion and bubble is 16 in race A and 18.7 in race B. The sequence of beaded — white — singed — vermilion — bubble is identical with the same region in race A. Beaded, white, singed, and vermilion are all alleles of race A (Beers unpublished, and Strinz 1936). The correct location of bubble is undetermined in race A. It may lie to the right or left of the spindle fiber which is about 16- units to the right of vermilion. If it were placed TABLE VI COMPARISON OF AVERAGE MAP DISTANCES OP RACE A WITH RACE B RACE A (Sturtevant DIS 1937, No. 7) 66.5 0____________Sjyug_______________________ 65.51 69.1 85 p bd wT V X 7 sn Spindle fiber region RACE B 52 n 50.2 |52.7___51.4 b d w s n j b u V S I to the left of the spindle fiber it would lie on the left limb of the X-chromosome• If placed to the right of the spindle fiber it would lie on the right limb of the X-chromosome (Dobzhansky unpublished). CHAPTER IV CYTOLOGICAL STUDY OF CERTAIN REGIONS OF THE CHROl&OSCMKES ()F ItACIG B Individual chromosomes may he distinguished in any nucleus, if one is acquainted with their distinctive character istics, especially in the region of their free ends. (Plate I) Dobzhansky and Tan (1936) divide the chromosomes of pseudoobscura race A into 100 arbitrary units, numbered conse cutively from the spindle fiber to the free end in each chromo some. Since sharpness and definiteness are essentials, each section begins with a conspicuous and easily recognized band. The division point is made just to the left of the chosen main band. The X-chromosome is divided into two equal parts which are known as the right and left limbs. The left limb (Plate II, Fig. l) is divided into sections 1-17. It is the shortest chromosome with the exception of the fifth. It ter minates in an oblong, square-headed bulb, showing a number of distinctive bands and vesiculated areas of which one band, lying at about the middle of section 16, is particularly heavy. Proximally the bulb is separated from the body of the chromo some by a neck-like constriction; the distal end is also marked by two heavy bands. The free end of the right limb (Plate II, Fig. 2) is inflated to form a disc-like structure that contains about four heavy bands. Proximal to the disc there is a light Tlate H IT 61 Tig 1 Fig. 1 Tlg.3 'A k*» s { : « Î 3 1 1 99 JX TT Tlg.^ Ti^.6 Characteristic. Tortious oi Chromosomes F ig.3" 9. T erm ina! p o r tio n s o l tV\e c h r o m o s o m e s i("L, 15/' Fl^. 6 3L- Chromosome 34 area, followed by two heavy and light bands lying rather close together. The right limb of the Z-chromosome is divided into sections 18-42. The second chromosome, which is the longest, is divided into sections 43-62. It has a terminal bulb show ing four heavy bands followed by two vesiculated discs. (Plate II, Fig, 3). The free end of the third chromosome possesses a prominent inflated region (Plate II, Fig. 4). Distal to this inflated area, which is devoid of prominent bands, is located a knob-like end portion with heavy discs. The fourth chromosome is divided into sections 82-t99. It has a conspi cuous terminal inflation which includes three heavy ba.nds (Plate II, Fig. 5). This region resembles the terminal por tion of the left limb of the X-chromosome. The fifth chromo some is so small that only under favorable conditions can it be seen (Plate II, Fig, 6). It is elliptical in shape, and shows several light bands designating section 100. INVERSIONS Race B varies from race A by having one inversion in each of the following chromosomes: the left and right limb of the X-chromosome, the second, and third. In the left limb of the X-chromosome sections 7-12 are inverted in race B, in the right limb of the X-chromosome sections 30-38 are inverted, in the second sections 52-56 are inverted, and in the third, sections 71-76 are inverted. These sections are numbered by Dobzhansky and Tan (1936) for race A and therefore the sequence 55 is not consecutive in race B due to interracial inversions (Plates V, VI, and VII). In addition to the interracial inversions, intra- racial ones also occur. One such inversion of race B is shown on Plate III. A diagrammatic explanation is shown in Figure la. a. figure V c>-^ Tlatcs HL a»vd 3Ï. Tlate m «-10H “ ■0 Confi^vA ration ofc an Inversion flate n rlO - 0 Coiv^i^uvat\ov\ ot aw Vtvviers'on, 38 At A the two homologous haploid strands, 1 and 2, are paired as normal in the diploid condition. Strands 1 and 2 separate into haploids and pair again through BCDE, forming a diploid chromosome. Then they become haploid once more before they pair again at F. By looking at the above Figure la it will be noticed that an inversion has taken place in either strand 1 or 2. Instead of having the sequence, ABCDEF, of the normal strand, one of the strands has the abnormal sequence, AEDCBF,BCDE having been inverted. In order that strand 1 and 2 may pair, a configuration as diagrammed above must take place. Plate IV shows a similar inversion and is diagrammed above in Fig. lb. NON-PAIRING BETWEEN HOMOLOGOUS CHROMOSOMES From the study of permanent slides of the salivary glands of the larvae, representative drawings of abnormal structures were made (Plates V-X). The individual repro duction of these chromosomes makes it difficult to recognize identical localities drawn by other workers. Moreover, varia tion in the amount of pressure in crushing the glands for the spreading of the chromosomes may have resulted in unequal stretching, crushing, etc. Plate V shows the result of non-pairing between homo logous chromosomes. This is the right limb of the X-chromo- some and shows a lack of pairing in sections 28, 29, and 38, 39 although identical bands appear on each strand, Plate VI also shows lack of pairing in the right limb of the X-chromosome. This lack of pairing involves sections 28, 29, and 38 which were shown on Plate V. It also extends as far as section 26. Identical bands are also present in both unpaired haploids. Plate VII shows a lack of pairing in the third chromosome involving sections 72, 73, 74, 75, 76, 70, and 69. Identical bands occur throughout. Plate VIII shows a lack of pairing from section 83- 86. The right strand in section 85 is stretched further than the left strand, so that identical bands do not lie opposite one another. Plate IX shows the unpaired terminal ends of the third chromosome, involving sections 80-81. Identical bands are present throughout. Plate X is a small region that does not pair, although the bands are identical. The ends of this chromosome could not be seen clearly and the region was so small that it could not be identified. Dr. Dobzhansky of the California Institute of Tech nology very kindly identified Plates V, VI, VII, and VIII from their respective slides. r i a t e ¥ - &? N,- - % T ottiow of R iglif LimVi oi X~ CViromosome Tlate H n r i o . ^ L L O V V PovVion Limb oi X“ CVvrom o-som e T l a U m 70 761 o 79J N, - April, 19 Z Twiddle Toirtion oi III- CKromosotwe riate Hiï 89 69 84/ 0 N. - 30 P r o x t m a l P o r t i o n o ( 13. C K ro ic n o s o m e TIate n ei 60, 0 80, M 0 T )is ^ a \ P o rtio n of m - C K ro m o s o m c T\ate ï M,- 30 S . F a rt of a n id e n litie à cVirom osoitie CHAPTER V SUMmRY (1) Recombination percentages were obtained for the sex-linked mutants beaded, white, singed, vermillion, and bubble. (2) The sequence of these loci is identical with the same region in race A. (3) Notch is not a deficiency for the white or vermilion loci. (4) The end regions of X-chromosome, second, third, fourth, and fifth chromosomes were identified and drawn. (5) Two inversions were recorded. (6) Abnormal chromosomes showed lack of pairing although identical bands were present. BIBLIOGRAPHY Baker, H.S., 1934, A Study of Certain X-ray Induced Mutations Drosophila nseudoobscura. Unpublished Master»s Thesis, University of Southern California, Los Angeles. 92 pp. Bauer, H., April, 1936,"Notes on permanent preparations of salivary gland chromosomes." D-i-S.., 6:35-36. Bridges, C.B., 1915, J. Ex p . Zool.. 19:1-21. . ., 1917, "Deficiency." Genetics. 2:445-465. . ., 1919, "Vermilion deficiency." J. Gen. Physiol.. 1: 645-656. . ., 1935, "Salivary chromosome maps." J. Heredity. Feb ruary 26:60. . ,, April, 1936a, "Current method for permanent aceto- carmine smears," D.£.S., 6:31-34, , ., April, 1936b, "The examination of salivary chromo somes." D.I.S., 6:37-40. . ., "Vapor method of changing reagents and of dehydra tion." Stain Technol.. 12:51-53, Bridges, C,B,, and T,H. Morgan, 1916, "Sex linked inheritance in Drosophila." Pub. Carnegie Inst. Washington. No. 237. Bridges, C.B., and Charles Metz, 1917, "Incompatibility of mutant races in Drosophila." Proc. Nat. Acad. Sei.. 3:673-678. Bridges, C.B., T.H. Morgan and A.A. Sturtevant, 1925, Genetics of Drosophila, pp. 163-172, Demerec, M., and M.E. Hoover, 1936, "Deficiencies in the fork ed region of the X-chromosome of Drosophila melanogaster." Amer. Nat.. 70:47. Dexter, F.S., 1916, "The analysis of a case of continuous var iation in Drosophila by a 'study of its linkage relations." Amer. Nat.. 48:712-738. Dobzhansky, T., 1933a, "On sterility of the interracial hybrids in Drosophila pseudoobscura." Proc. Nat. Acad. Sci.. 19: 397-403. 47 . • . March 1935, "Racial variability and the distribution of races." , 3:42-43. Dobzhansky, T., and E.O. Boohe, 1933b, "Intersterile races of Drosophila pseudoobscura Frol." Biol. Zbl., 53:314-330. Dobzhansky, T., and G.W. Beadle, 1936, "Studies on hybrid ster- itity IV - Transplanted testes in Drosophila pseudoobscura." Genetics. 21:832-840. Dobzhansky, T., and C.G. Tan, 1936, "Studies in hybrid sterility III." Z.I.A.V., 72, Heft. 1. Donald, A.P., 1936, "On the genetical constitution of Drosophila pseudo-obscufa, Race A." J. of Genetics. 33:104-122. Koller, P.O., 1932a, "The relation of fertility factors to cross ing over in Drosophila obscura hybrids."- Z.I_.A.V., 60:137- 151. . . , 1932b, "Pointed and the constitution of the X-chromo some in Drosophila obscura." J. of Genetics. 26:213-229. . . . ., 1934, "Spermatogenesis in Drosophila pseudoobscura Frolowa II. The cytological basis of sterility of hybrid males of race A and B," Proc. Roval Soc. Edinburgh. 1:67- 87. . . . ., 1936, "Structural hybridity in Drosophila pseudoobscura." J. ^ Genetics. 32:79-102. Lancefield, D.E., 1922, "Linkage relations of the sex-linked characters in Drosophila obscura." Genetics. 7:335-384. . .. ., 1925, "An interracial cross in Drosophila obscura pro ducing partially fertile hybrids." Anat. Record. 31:4, Abstract pp. 346. . . . ., 1929, "A genetic study of crosses of two races or physiol ogical species of Drosophila obscura." ^.i-A.V., 53:287-317. Marshak, A., 1936, "A rapid method for making permanent mounts of a salivary gland chromosome of Drosophila." D.I_.8_., 6: 30-31. Mohr, O.L., 1919, "Character changes caused by mutations of an entire region of chromosomes in Drosophila." Genetics. 4: 273-286. Painter, T.S., 1934a, "A new method for the study of chromosomes abberrations and the plotting of chromosome maps in Droso phila melanogaster." Genetics, 19:175-189. 49 • • • ♦, 1934b, "The morphology of the X-chromosome in salivary glands of Drosophila melanogaster and a new type of chromo some map for this element." Genetics. 19:448-469. . . . ., 1936, "Aceto-carmine technique for salivary chromosomes.” D.I.S., 6:30. Patterson, J.T., 1932, "Lethal mutations and deficiencies produced in the X-chromosomes of Drosophila melanogaster by X-radia- tion.” Amer. Hat.. 66:193-206. Poulson, D.F., 1934, "Times of development of the two races of Drosophila pseudoobscura." J. Exp. Zool.. 68:237-245. Schultz, J., 1936, "Notes on methods for salivary chromosomes." D.I.S., 6:34-35. Smith, R.J., 1934, "Genetic studies on Drosophila pseudoobscura Race B." Unpublished Master’s thesis. University of Southern California, Los Angeles, 134 pp. Strinz, R., 1936, "Genetic studies on mutations of Drosophila pseudoobscura. Race B." Unpublished Master’s thesis. University of Southern California, Los Angeles, 94 pp. Sturtevant, A.H., 1926, "A cross over reducer in Drosophila melanogaster due to inversion of a section of the 3rd chromosome." Biol. Zbl.. 43:697-702. Tan, C.C., 1935, "Salivary gland chromosomes in the two races of Drosophila pseudoobscura." 20:392-402.

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Creator Niemetz, David (author)

Core Title Cytological and genetical study of certain regions of the chromosomes in Drosophila pseudoobscura

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