DOCSLIB.ORG

Early-Stage Evolution of the Neo-Y Chromosome in Drosophila

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Early-Stage Evolution of the Neo-Y Chromosome in Drosophila Zoological Studies 50(3): 338-349 (2011) Early-Stage Evolution of the Neo-Y Chromosome in Drosophila albomicans Chia-Hao Cheng1, Ching-Ho Chang2, and Hwei-yu Chang1,3,* 1Department of Entomology, National Taiwan Univ., Taipei 106, Taiwan 2Institute of Ecology and Evolutionary Biology, National Taiwan Univ., Taipei 106, Taiwan 3Biodiversity Research Center, Academia Sinica, Nankang, Taipei 115, Taiwan (Accepted December 27, 2010) Chia-Hao Cheng, Ching-Ho Chang, and Hwei-yu Chang (2011) Early-stage evolution of the neo-Y chromosome in Drosophila albomicans. Zoological Studies 50(3): 338-349. Numerous theories have specified that an originally autosomal neo-Y chromosome arm is expected to undergo degenerative evolution. Neo- sex chromosomes of Drosophila albomicans originated from 2 Robertsonian translocation events, one for X and the other for Y, between ancestral Drosophila sex chromosomes and a pair of autosomes homologous to the 3rd chromosomes of its sibling species D. nasuta. Since the neo-sex chromosome in D. albomicans is still evolutionarily young, we used genetic approaches to reveal changes in the entire neo-Y chromosome. Non-disjunction is an indicator used to investigate differences between homologous chromosomes. In this study, we first confirmed that no male recombination had occurred in hybrid males of these 2 sibling species. With the aid of molecular marker genotyping and direct karyotyping of aneuploid offspring produced through specially designed crosses and backcrosses of fertile hybrids, we found that the non-disjunction rate was significantly higher in hybrid males with the neo-Y chromosome than in hybrids without it. The high non- disjunction rate made it possible to generate 3,X,X/neo-Y F2 females and X,neo-Y/neo-Y F3 male offspring which can reveal recessive effects of the homozygous 3rd chromosome arm. Results of this aneuploid study revealed severe recessive inviability of the neo-Y chromosome. Our results further suggested that increased non-disjunction in hybrid males with the neo-Y chromosome is likely due to changes that occurred on the Y arm, whereas recessive deleterious alleles might be located on the 3rd arm of the neo-Y chromosome. Taken together, the elevated non-disjunction rate and severe recessive inviability revealed significant changes in the neo-Y chromosome at this early stage of chromosome evolution in D. albomicans. http://zoolstud.sinica.edu.tw/Journals/50.3/338.pdf Key words: Meiosis, Neo-sex chromosome, Non-disjunction, Recessive deleterious allele. Neo-sex chromosomes which formed by (Charlesworth and Charlesworth 2000). For fusion events between sex chromosomes and example, the neo-Y chromosome of D. miranda, autosomes have independently evolved in many the neo-sex chromosomes of which diverged more Drosophila lineages. Due to achiasmatic meiosis than 106 yr ago (Ma), has accumulated many found in male Drosophila (Morgan 1912), the deleterious mutations and transposable elements neo-Y chromosome which only exists in males (Bachtrog and Charlesworth 2002, Bachtrog might lack recombination after fused chromosomes 2005). In another case, the neo-Y chromosome being fixed in the population. A non-recombining of D. psudoobscura has lost most of its genes neo-Y chromosome was predicted to degenerate and heterochromatinized since it diverged from due to Muller’s ratchet, background selection, the neo-X about 18 Ma (Carvalho and Clark the Hill-Robertson effect, and selective sweep 2005). Although those studies showed obvious * To whom correspondence and reprint requests should be addressed. Chia-Hao Cheng and Ching-Ho Chang contribute equally to this work. E-mail:[email protected] 338 Cheng et al. – Neo-Y of Drosophila albomicans 339 degeneration due to the lack of recombination a YY individual cannot survive in an XY sex- in neo-Y chromosomes, early changes after the determination system. Instead, non-disjunction, fixation of neo-sex chromosomes are still unclear. an abnormal whole-chromosome behavior, may Examining a Drosophila species with a younger serve as an indicator to reveal the divergence neo-sex chromosome system would be helpful in among sex-related chromosomes. Aneuploids answering this question. with an abnormal number of ancestral-type sex Drosophila albomicans has a pair of neo- chromosomes (i.e., X or Y chromosome of D. sex chromosomes and can be crossed with its nasuta) caused by non-disjunction are frequently allopatrically distributed sibling species, D. nasuta found in hybrid populations derived from these (Kitagawa et al. 1982). The neo-sex system 2 sibling species (Yu et al. 1999). This non- appears in every D. albomicans lineage but is disjunction may indicate mispairing between these totally absent from other species of the D. nasuta inter-specific chromosomes. Although the pairing subgroup (Meera Rao and Ranganath 1991, of homologous chromosomes, which is essential Chang et al. 2008). This fact implies that the for segregating them into 2 separate gametes, is age of the neo-sex system of D. albomicans is a nearly universal feature of sexual reproduction, even younger than species divergence, which is non-disjunction was discovered in D. melanogaster estimated to have occurred < 0.5 Ma (Chang et al. nearly 100 yr ago (Bridge 1913 1916). This non- 1989, Bachtrog 2006). According to homology, we disjunction can be used as a special tool for call these 2 fused parts the Y (or X) arm and the different genetic analyses; for instance, it may 3rd arm of the neo-sex chromosome in this study. generate X,neo-Y/neo-Y individuals which could Since the divergence period is not sufficiently long, provide a new chance to investigate recessive neither the differential substitution rate between inferiority of the neo-Y of D. albomicans. the neo-X and neo-Y nor obvious degeneration Genetic markers can serve as fundamental of the neo-Y chromosome was observed on the tools to reveal the non-disjunction rate of hybrids 3rd chromosome arms by a sequence analysis and the accumulation of recessive deleterious (Chang 2008). However, those results could not alleles. We previously established several rule out other changes such as meiotic behavior molecular markers (Chang et al. 2008) which and an accumulation of deleterious alleles on can be used for easy and rapid detection of the entire neo-sex chromosome. In our previous hybrid non-disjunction under the prerequisite study, a free 3rd autosome (i.e., not fused to a of“no male recombination”. No crossing- sex chromosome) acquired from D. nasuta was over during meiosis in male D. melanogaster fixed in certain hybrid strains and behaved like a of the subgenus Sophophora was first reported Y chromosome without recombination (Chang and by Morgan (1912), and achiasmatic meiosis is Kung 2008). Homozygotes of this chromosome, characteristic of nearly all higher dipteran males, which was designated a Y-like chromosome, can like Drosophila (Gethmann 1988). However, even be obtained by backcrossing males from this in the Sophophora subgenus, an appreciable strain to D. nasuta. Our study revealed that the level of spontaneous male recombination was fitness of individuals carrying homozygous Y-like discovered in D. ananassae (Kikkawa 1938). chromosomes began to decline within a few Since D. albomicans is classified into the subgenus hundred generations (Chang and Kung 2008). Drosophila which diverged from Sophophora more Therefore, the 3rd chromosome arm of the neo-Y than 60 Ma (Beverley and Wilson 1984, Tamura et in D. albomicans is expected to degenerate due to al. 2004), whether it also lacks male recombination the accumulation of recessive deleterious alleles requires experimental support. after millions of generations without recombination. In this study, genetic experiments were Accordingly, we suspect that examining conducted to understand this early stage changes at the chromosome level may be more of evolution of the neo-sex chromosome by accessible than averaging substitution rates or investigating hybrid offspring of these 2 sibling finding non-functional evidence from randomly species. Reciprocal crosses between D. chosen genes on the chromosome at this early albomicans and D. nasuta can produce 3 kinds of stage of evolution of the neo-Y chromosome. (2 male and 1 female) hybrids with different sex- In principle, the accumulation of recessive related chromosome configurations (3,X/neo-Y; deleterious alleles on the neo-Y chromosome 3,Y/neo-X; and 3,X/neo-X in Fig. 1). The non- could be examined by the survival rate of disjunction rate of these hybrids can be estimated individuals homozygous for the neo-Y. However, by aneuploid offspring produced through specially 340 Zoological Studies 50(3): 338-349 (2011) designed crossing schemes with proper genotyping Chang and Tai 2007). All crosses were made or karyotyping. In addition, the backcross of a 3,X/ using 4-d-old virgin flies, and the flies were sexed neo-Y male to a D. nasuta female can produce 3,X/ within 8 h after emergence. X,neo-Y female offspring due to non-disjunction. In this study, crossing schemes 1 to 6 were Afterwards, backcrossing these aneuploid females designed to determine the recombination rates of to D. albomicans males may produce X,neo-Y/ sex chromosomes in D. albomicans (1 and 2) and neo-Y males homozygous for the 3rd chromosome non-disjunction rates in hybrid offspring (3, 4, and arm. Through these genetic approaches, we 5), and to detect recessive deleterious alleles on were able to reveal the existence of recessive the neo-Y chromosome (6). Two separate pairs deleterious alleles on the neo-Y chromosome if of each crossing scheme were established in those XYY males were absent or rare. the beginning as 2 repeats instead of generating repeats in subsequent generations. In general, 20 offspring were genotyped as 1 sample. MATERIALS AND METHODS Molecular markers Drosophila strains and crossing schemes Four loci with inter-specific differences Inbred strains D. albomicans #163.5- between D.
Load more

Recommended publications
  • University of Mysore
    Biodata of Dr. N. B. RAMACHANDRA Ph.D, FASc PROFESSOR, AND PRINCIPAL INVESTIGATOR Chairman - Department of Studies in Genetics and Genomics Chairman- Board of Studies in Genetics and Genomics Deputy Coordinator for UGC-SAP (CAS-1), DOS in Zoology Director- University of Mysore Genome Centre (Local Secretary - 103rd Indian Science Congress 2016 Former Chairman-Board of Studies in Zoology (UG&PG) & BOS in Clinical Research & Clinical Data Management) University of Mysore, Manasagangotri, Mysuru – 570 006, INDIA [email protected] / [email protected] http://scholar.google.co.in/citations?user=CBqZv1oAAAAJ http://www.ramachandralab.com/ Phone: 0821-2419781/888 (O) ; Mobile: 09880033687 1. Date of Birth: 31.05.1958 2. Educational Qualification: 1982-88: Ph.D. in Zoology, Department of Zoology, University of Mysore, INDIA. Thesis title: "Contributions to population cytogenetics of Drosophila: Studies on interracial hybridization and B-chromosomes". 1980-82: M.Sc. in Zoology, 1st Class with 2nd Rank, University of Mysore, Mysore. 1977-80: B.Sc. (Chemistry, Botany, and Zoology), 1st class, Cauvery College, Gonicoppal, University of Mysore, INDIA. 3. Area of Specialization: 1) Drosophila Genetics and Evolution 2) Human Genetic Diseases and Genomics 4. Awards/ Recognitions: Sl.No. Year Recognition Institution “Best boy of the college” Cauvary College, Gonicoppal, Univ. 1 1980 award of Mysore. 2 1982 II Rank in M.Sc DOS in Zoology, Univ. of Mysore. Government of India Nehru Department of Biological sciences, 3 1990 Centenary British Fellowship Warwick University, Coventry, United (common wealth) Award Kingdom (not availed). 1990 - McMaster University, Department of 4. 1992 Post Doctoral Fellow Award Biochemistry, Canada University of California, Department of 1999- Senior Research Associate 5 Cell Molecular and Developmental 2000 II award Biology, Los Angeles, USA VISITING PROFESSOR- to Dept.
    [Show full text]
  • Analysis of Drosophila Buzzatii Transposable Elements Doctoral
    Analysis of Drosophila buzzatii transposable elements Doctoral Thesis Nuria Rius Camps Departament de Genetica` i de Microbiolog`ıa, Universitat Autonoma de Barcelona, Bellaterra (Barcelona), Spain Memoria` presentada per la Llicenciada en Biologia Nuria Rius Camps per a optar al grau de Doctora en Genetica.` Nuria Rius Camps Bellaterra, a 23 de novembre de 2015 El Doctor Alfredo Ruiz Panadero, Catedratic` del Departament de Genetica` i Microbiologia de la Fac- ultat de Biociencies` de la Universitat Autonoma` de Barcelona, CERTIFICA que Nuria Rius Camps ha dut a terme sota la seva direccio´ el treball de recerca realitzat al Departament de Genetica` i Microbiologia de la Facultat de Biociencies` de la Universitat Autonoma` de Barcelona que ha portat a l’elaboracio´ d’aquesta Tesi Doctoral titulada “Analysis of Drosophila buz- zatii transposable elements”. I perque` consti als efectes oportuns, signa el present certificat a Bellaterra, a 23 de novembre de 2015 Alfredo Ruiz Panadero I tell you all this because it’s worth recognizing that there is no such thing as an overnight success. You will do well to cultivate the resources in yourself that bring you happiness outside of success or failure. The truth is, most of us discover where we are headed when we arrive. At that time, we turn around and say, yes, this is obviously where I was going all along. It’s a good idea to try to enjoy the scenery on the detours, because you’ll probably take a few. (Bill Watterson) CONTENTS Abstract iii Resumen v 1. Introduction 1 1.1. Transposable elements .......................... 1 1.1.1.
    [Show full text]
  • Downloaded Transcribed from an RNA Template Directly Onto a Consensus Sequences of Jockey Families Deposited in the Tambones Et Al
    Tambones et al. Mobile DNA (2019) 10:43 https://doi.org/10.1186/s13100-019-0184-1 RESEARCH Open Access High frequency of horizontal transfer in Jockey families (LINE order) of drosophilids Izabella L. Tambones1, Annabelle Haudry2, Maryanna C. Simão1 and Claudia M. A. Carareto1* Abstract Background: The use of large-scale genomic analyses has resulted in an improvement of transposable element sampling and a significant increase in the number of reported HTT (horizontal transfer of transposable elements) events by expanding the sampling of transposable element sequences in general and of specific families of these elements in particular, which were previously poorly sampled. In this study, we investigated the occurrence of HTT events in a group of elements that, until recently, were uncommon among the HTT records in Drosophila – the Jockey elements, members of the LINE (long interspersed nuclear element) order of non-LTR (long terminal repeat) retrotransposons. The sequences of 111 Jockey families deposited in Repbase that met the criteria of the analysis were used to identify Jockey sequences in 48 genomes of Drosophilidae (genus Drosophila, subgenus Sophophora: melanogaster, obscura and willistoni groups; subgenus Drosophila: immigrans, melanica, repleta, robusta, virilis and grimshawi groups; subgenus Dorsilopha: busckii group; genus/subgenus Zaprionus and genus Scaptodrosophila). Results: Phylogenetic analyses revealed 72 Jockey families in 41 genomes. Combined analyses revealed 15 potential HTT events between species belonging to different
    [Show full text]
  • Genome Size Evolution Differs Between Drosophila Subgenera with Striking Differences in Male and Female Genome Size in Sophophora
    INVESTIGATION Genome Size Evolution Differs Between Drosophila Subgenera with Striking Differences in Male and Female Genome Size in Sophophora Carl E. Hjelmen,*,†,1 Heath Blackmon,† V. Renee Holmes,* Crystal G. Burrus,† and J. Spencer Johnston* *Department of Biology and †Department of Entomology, Texas A&M University, College Station, TX 77843 ORCID IDs: 0000-0003-3061-6458 (C.E.H.); 0000-0002-5433-4036 (H.B.); 0000-0002-1034-3707 (V.R.H.); 0000-0003-4792-2945 (J.S.J.) ABSTRACT Genome size varies across the tree of life, with no clear correlation to organismal complexity or KEYWORDS coding sequence, but with differences in non-coding regions. Phylogenetic methods have recently been Genome size incorporated to further disentangle this enigma, yet most of these studies have focused on widely diverged sex chromosome species. Few have compared patterns of genome size change in closely related species with known Drosophila structural differences in the genome. As a consequence, the relationship between genome size and phylogenetic differences in chromosome number or inter-sexual differences attributed to XY systems are largely comparative unstudied. We hypothesize that structural differences associated with chromosome number and X-Y methods chromosome differentiation, should result in differing rates and patterns of genome size change. In this study, we utilize the subgenera within the Drosophila to ask if patterns and rates of genome size change differ between closely related species with differences in chromosome numbers and states of the XY system. Genome sizes for males and females of 152 species are used to answer these questions (with 92 newly added or updated estimates).
    [Show full text]
  • Evidence for No Sexual Isolation Between Drosophila Albomicans and D.Nasuta
    Evidence for no sexual isolation between Drosophila albomicans and D. nasuta Yong-Kyu Kim1,3, Dennis R. Phillips2 & Yun Tao1 1Department of Biology, Emory University, Atlanta, Georgia 30322 2Department of Chemistry, University of Georgia, Athens, Georgia 30602 3Present address: Howard Hughes Medical Institute, Janelia Farm Research Campus, 19700 Helix Drive, Ashburn, Virginia 20147 Keywords Abstract Courtship, cuticular hydrocarbons, D. albomicans, D. nasuta, mating behavior, Sexual isolation, the reduced tendency to mate, is one of the reproductive barri- speciation. ers that prevent gene flow between different species. Various species-specific sig- nals during courtship contribute to sexual isolation between species. Drosophila Correspondence albomicans and D. nasuta are closely related species of the nasuta subgroup Yong-Kyu Kim, Howard Hughes Medical within the Drosophila immigrans group and are distributed in allopatry. We Institute, Janelia Farm Research Campus, analyzed mating behavior and courtship as well as cuticular hydrocarbon 19700 Helix Drive, Ashburn, VA 20147. profiles within and between species. Here, we report that these two species Tel: (571) 209-4180; Fax: (571) 209-4941; E-mail: [email protected] randomly mated with each other. We did not observe any sexual isolation between species or between strains within species by multiple-choice tests. Significant Funding Information difference in the courtship index was detected between these two species, but This study was supported by National males and females of both species showed no discrimination against heterospec- Institutes of Health R01 HD060679. ific partners. Significant quantitative variations in cuticular hydrocarbons between these two species were also found, but the cuticular hydrocarbons Received: 18 February 2013; Revised: 22 April 2013; Accepted: 1 May 2013 appear to play a negligible role in both courtship and sexual isolation between these two species.
    [Show full text]
  • Genetics on the Fly: a Primer on the Drosophila Model System
    GENETICS | PRIMER Genetics on the Fly: A Primer on the Drosophila Model System Karen G. Hales,*,1 Christopher A. Korey,† Amanda M. Larracuente,‡ and David M. Roberts§ *Department of Biology, Davidson College, Davidson North Carolina 28035, †Biology Department, College of Charleston, Charleston, South Carolina 29424, ‡Department of Biology, University of Rochester, Rochester, New York 14627, and §Biology Department, Franklin and Marshall College, Lancaster, Pennsylvania 17604 ABSTRACT Fruit flies of the genus Drosophila have been an attractive and effective genetic model organism since Thomas Hunt Morgan and colleagues made seminal discoveries with them a century ago. Work with Drosophila has enabled dramatic advances in cell and developmental biology, neurobiology and behavior, molecular biology, evolutionary and population genetics, and other fields. With more tissue types and observable behaviors than in other short-generation model organisms, and with vast genome data available for many species within the genus, the fly’s tractable complexity will continue to enable exciting opportunities to explore mechanisms of complex developmental programs, behaviors, and broader evolutionary questions. This primer describes the organism’s natural history, the features of sequenced genomes within the genus, the wide range of available genetic tools and online resources, the types of biological questions Drosophila can help address, and historical milestones. KEYWORDS Drosophila; development; comparative genomics; model organism; TABLE OF CONTENTS
    [Show full text]
  • Drosophila Information Service
    Drosophila Information Service Number 103 December 2020 Prepared at the Department of Biology University of Oklahoma Norman, OK 73019 U.S.A. ii Dros. Inf. Serv. 103 (2020) Preface Drosophila Information Service (often called “DIS” by those in the field) was first printed in March, 1934. For those first issues, material contributed by Drosophila workers was arranged by C.B. Bridges and M. Demerec. As noted in its preface, which is reprinted in Dros. Inf. Serv. 75 (1994), Drosophila Information Service was undertaken because, “An appreciable share of credit for the fine accomplishments in Drosophila genetics is due to the broadmindedness of the original Drosophila workers who established the policy of a free exchange of material and information among all actively interested in Drosophila research. This policy has proved to be a great stimulus for the use of Drosophila material in genetic research and is directly responsible for many important contributions.” Since that first issue, DIS has continued to promote open communication. The production of this volume of DIS could not have been completed without the generous efforts of many people. Except for the special issues that contained mutant and stock information now provided in detail by FlyBase and similar material in the annual volumes, all issues are now freely-accessible from our web site: www.ou.edu/journals/dis. For early issues that only exist as aging typed or mimeographed copies, some notes and announcements have not yet been fully brought on line, but key information in those issues is available from FlyBase. We intend to fill in those gaps for historical purposes in the future.
    [Show full text]
  • Metabolic Rate and Hypoxia Tolerance Are Affected by Group Interactions
    © 2017. Published by The Company of Biologists Ltd | Biology Open (2017) 6, 471-480 doi:10.1242/bio.023994 RESEARCH ARTICLE Metabolic rate and hypoxia tolerance are affected by group interactions and sex in the fruit fly (Drosophila melanogaster): new data and a literature survey Warren Burggren1,*, BriAnna M. Souder1 and Dao H. Ho2 ABSTRACT Melvin et al., 2007; Miquel et al., 1982; Partridge et al., 2005; Population density and associated behavioral adjustments are Promislow and Haselkorn, 2002; Van Voorhies et al., 2003, 2004b). potentially important in regulating physiological performance in Metabolic rate in Drosophila has also been investigated in the many animals. In r-selected species like the fruit fly (Drosophila), context of specific genotypes (Hoekstra and Montooth, 2013; where population density rapidly shifts in unpredictable and unstable Jensen et al., 2014; Jumbo-Lucioni et al., 2010; Montooth et al., environments, density-dependent physiological adjustments may aid 2003; Stone et al., 2013), to reveal how genotype underpins specific survival of individuals living in a social environment. Yet, how metabolic phenotypes. Metabolic rate has also been measured for population density (and associated social behaviors) affects insight into how specific metabolic pathways affect energy physiological functions like metabolism is poorly understood in metabolism (Barros et al., 1991; Isobe et al., 2013). The study of insects. Additionally, insects often show marked sexual dimorphism function and limitations of gas exchange by a tracheal system have (larger females). Thus, in this study on D. melanogaster,we also involved metabolic rate measurements (Klok et al., 2010; characterized the effects of fly density and sex on both mass- Merkey et al., 2011; Mölich et al., 2012).
    [Show full text]
  • Host – Parasitoid Interaction in Drosophila – Leptopilina System
    Host – parasitoid interaction in Drosophila – Leptopilina system Tomohiro Takigahira A dissertation submitted to the Graduate School of Environmental and Life Science, Okayama University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2018 Contents Acknowledgments .......................................................................................................... 1 General Introduction ...................................................................................................... 2 Chapter I. Assessment of fitness costs of resistance against the parasitoid Leptopilina vectoriae in Drosophila bipectinata............................................................. 9 I-1. Introduction ............................................................................................................... 9 I-2. Materials and Methods ............................................................................................. 12 I-2-1. Selection for parasitoid resistance ..................................................................... 12 I-2-2. Measurements of life history and stress tolerance traits .................................... 14 I-2-3. Resistance against other parasitoids .................................................................. 17 I-2-4. Data analysis ......................................................................................................... 18 I-3. Results .....................................................................................................................
    [Show full text]
  • Metaphase Chromosome Configuration of the Immigrans Species Group of Drosophila
    Jpn. J. Genet. (1983) 57, pp. 315-326 Metaphase chromosome configuration of the immigrans species group of Drosophila BY Ken-Ichi WAKAHAMA*,Tamiko SHINOHARA**,Machiko HATsUMI***, Satoko UCHIDA**** and Osamu KITAGAWA*** *Department of Biology , Shimane University, **Department of Human Cytogenetics, Japan Red Cross Medical Center, ***Department of Biology, Tokyo Metropolitan University and ****Ono Pharmaceutical Co. Ltd. (Received February 11, 1983) ABSTRACT Metaphase chromosome configurations of 23 species and subspecies belong- ing to five subgroups of the immigrans species group of Drosophila were examined by the Giemsa staining method, from the point of view of the phylogenetic relationships in this species group. New to science are the descriptions of the karyotypes of five species, Taxon-C, Taxon-F, D, nivei f rons,, D. quadrilineata and D, neohypocausta which are 2n=8, 2R+1V+1D; 2n=8, 2R+1V+1D; 2n=8, 2R+1V+1D; 2n =12, 4R+ 1V+ 1D; and 2n = 6, 2R+ 1V, respectively. The karyotypes of the other species were also examined and compared with earlier descriptions. Some of our observations agreed with earlier ones but the remainder showed some major or minor differences from the previous reports. The basic karyotype of the species belonging to the immigrans species group was 2n=8, 2R+1V+1D (or short rod). The karyotypes of D. annul ipes and D. quadrilineata of the D. quadrilineata subgroup, of D, argentostriata and D, silvistriata of the D, lineosa subgroup and of D, neohypocausta of the D. hypocausta subgroup differed fundamentally from the basic type of the immigrans species group. These five species might be somewhat remote from the other species of the immigrans group.
    [Show full text]
  • Sex Ratio Distortion in Hybrids of Drosophila Albomicans and D. Nasuta
    Zoological Studies 43(3): 622-628 (2004) Sex Ratio Distortion in Hybrids of Drosophila albomicans and D. nasuta Yung-Yu Yang1, Fei-Jann Lin2 and Hwei-yu Chang1,2,* 1Department of Entomology, National Taiwan University, Taipei, Taiwan 106, R.O.C. 2Institute of Zoology, Academia Sinica, Nankang, Taipei, Taiwan 115, R.O.C. (Accepted June 5, 2004) Yung-Yu Yang, Fei-Jann Lin and Hwei-yu Chang (2004) Sex ratio distortion in hybrids of Drosophila albomi- cans and D. nasuta. Zoological Studies 43(3): 622-628. A sex-ratio distorter in Drosophila albomicans was uncovered by the hybridization between Japanese Okinawa D. albomicans females and Indian D. nasuta males. The F1 male from this cross produces female-biased offspring. The genic nature demonstrated in the present study suggests that meiotic drive instead of non-disjunction of the sex chromosomes during meiosis is the major cause for this. The meiotic driver was found to be located on the neo-X chromosome of D. albomi- cans, whose genome also contains drive suppressors, while that of D. nasuta is suppressor-free. In addition, hybrid F1 and F2 males were found to be semisterile probably due to an interaction between the 3rd and Y chro- mosomes of D. nasuta and the autosomes of D. albomicans. http://www.sinica.edu.tw/zool/zoolstud/43.3/622.pdf Key words: Drosophila albomicans, D. nasuta, Meiotic drive, Sex-ratio distortion. Most bisexual populations with an XY sex may become fixed in a population even if that is determination system have a sex ratio of around disadvantageous. Hence, they suggested that 1:1 (Bull 1983).
    [Show full text]
  • The Evolution of Expression in Drosophila by Lauren B. Gibilisco a Dissertation Submitted in Partial Satisfaction of the Require
    The Evolution of Expression in Drosophila by Lauren B. Gibilisco A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Integrative Biology in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Doris Bachtrog, Chair Professor Rasmus Nielsen Professor Donald Rio Fall 2017 Abstract The Evolution of Expression in Drosophila by Lauren B. Gibilisco Doctor of Philosophy in Integrative Biology University of California, Berkeley Professor Doris Bachtrog, Chair Genomes have evolved multiple ways to regulate gene expression. Alternative splicing of genes is a strategy by which more than one transcript and/or protein can be encoded by a single gene. For cases in which expression is harmful, genomes have evolved strategies to repress expression. Epigenetic modifications, and in particular repressive heterochromatin, can repress expression. RNAi, which uses sequence homology to target transcripts for degradation, is another strategy that has evolved to control expression. I characterized alternative splicing (“AS") within and between Drosophila species, sexes, tissues, and developmental stages. Alternative pre-mRNA splicing (“AS”) greatly expands proteome diversity, but little is known about the evolutionary landscape of AS in Drosophila and how it differs between embryonic and adult stages or males and females. I studied the transcriptomes from several tissues and developmental stages in males and females from four species across the Drosophila genus. I found that 20–37% of multi-exon genes are alternatively spliced. While males generally express a larger number of genes, AS is more prevalent in females, suggesting that the sexes adopt different expression strategies for their specialized function.
    [Show full text]