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Bellott DW, Page DC. Dosage-sensitive functions in embryonic development drove the survival of genes on sex-specific chromosomes in snakes, birds, and mammals. Genome Res 2021; 31:198-210. [PMID: 33479023 PMCID: PMC7849413 DOI: 10.1101/gr.268516.120] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 12/04/2020] [Indexed: 12/18/2022]
Abstract
Different ancestral autosomes independently evolved into sex chromosomes in snakes, birds, and mammals. In snakes and birds, females are ZW and males are ZZ; in mammals, females are XX and males are XY. Although X and Z Chromosomes retain nearly all ancestral genes, sex-specific W and Y Chromosomes suffered extensive genetic decay. In both birds and mammals, the genes that survived on sex-specific chromosomes are enriched for broadly expressed, dosage-sensitive regulators of gene expression, subject to strong purifying selection. To gain deeper insight into the processes that govern survival on sex-specific chromosomes, we carried out a meta-analysis of survival across 41 species-three snakes, 24 birds, and 14 mammals-doubling the number of ancestral genes under investigation and increasing our power to detect enrichments among survivors relative to nonsurvivors. Of 2564 ancestral genes, representing an eighth of the ancestral amniote genome, only 324 survive on present-day sex-specific chromosomes. Survivors are enriched for dosage-sensitive developmental processes, particularly development of neural crest-derived structures, such as the face. However, there was no enrichment for expression in sex-specific tissues, involvement in sex determination or gonadogenesis pathways, or conserved sex-biased expression. Broad expression and dosage sensitivity contributed independently to gene survival, suggesting that pleiotropy imposes additional constraints on the evolution of dosage compensation. We propose that maintaining the viability of the heterogametic sex drove gene survival on amniote sex-specific chromosomes, and that subtle modulation of the expression of survivor genes and their autosomal orthologs has disproportionately large effects on development and disease.
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Affiliation(s)
| | - David C Page
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Laopichienpong N, Kraichak E, Singchat W, Sillapaprayoon S, Muangmai N, Suntrarachun S, Baicharoen S, Peyachoknagul S, Chanhome L, Ezaz T, Srikulnath K. Genome-wide SNP analysis of Siamese cobra (Naja kaouthia) reveals the molecular basis of transitions between Z and W sex chromosomes and supports the presence of an ancestral super-sex chromosome in amniotes. Genomics 2020; 113:624-636. [PMID: 33002626 DOI: 10.1016/j.ygeno.2020.09.058] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/10/2020] [Accepted: 09/28/2020] [Indexed: 10/23/2022]
Abstract
Elucidation of the process of sex chromosome differentiation is necessary to understand the dynamics of evolutionary mechanisms in organisms. The W sex chromosome of the Siamese cobra (Naja kaouthia) contains a large number of repeats and shares amniote sex chromosomal linkages. Diversity Arrays Technology provides an effective approach to identify sex-specific loci that are epoch-making, to understand the dynamics of molecular transitions between the Z and W sex chromosomes in a snake lineage. From a total of 543 sex-specific loci, 90 showed partial homology with sex chromosomes of several amniotes and 89 loci were homologous to transposable elements. Two loci were confirmed as W-specific nucleotides after PCR amplification. These loci might result from a sex chromosome differentiation process and involve putative sex-determination regions in the Siamese cobra. Sex-specific loci shared linkage homologies among amniote sex chromosomes, supporting an ancestral super-sex chromosome.
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Affiliation(s)
- Nararat Laopichienpong
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
| | - Ekaphan Kraichak
- Department of Botany, Kasetsart University, Bangkok 10900, Thailand.
| | - Worapong Singchat
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
| | - Siwapech Sillapaprayoon
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
| | - Narongrit Muangmai
- Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand
| | - Sunutcha Suntrarachun
- Snake Farm, Queen Saovabha Memorial Institute, the Thai Red Cross Society, Bangkok 10330, Thailand
| | - Sudarath Baicharoen
- Bureau of Conservation and Research, Zoological Park Organization under the Royal Patronage of His Majesty the King, Bangkok 10300, Thailand
| | - Surin Peyachoknagul
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand.
| | - Lawan Chanhome
- Snake Farm, Queen Saovabha Memorial Institute, the Thai Red Cross Society, Bangkok 10330, Thailand
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, 2617, Australia.
| | - Kornsorn Srikulnath
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, 50 Ngamwongwan, Chatuchak, Bangkok 10900, Thailand; Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University, Kasetsart University, Bangkok 10900, Thailand, (CASTNAR, NRU-KU, Thailand); Center of Excellence on Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok 10900, Thailand; Omics Center for Agriculture, Bioresources, Food and Health, Kasetsart University (OmiKU), Bangkok 10900, Thailand; Amphibian Research Center, Hiroshima University, 1-3-1, Kagamiyama, Higashihiroshima 739-8526, Japan.
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Yazdi HP, Ellegren H. A Genetic Map of Ostrich Z Chromosome and the Role of Inversions in Avian Sex Chromosome Evolution. Genome Biol Evol 2018; 10:2049-2060. [PMID: 30099482 PMCID: PMC6105114 DOI: 10.1093/gbe/evy163] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2018] [Indexed: 12/11/2022] Open
Abstract
Recombination arrest is a necessary step for the evolution of distinct sex chromosomes. Structural changes, such as inversions, may represent the mechanistic basis for recombination suppression and comparisons of the structural organization of chromosomes as given by chromosome-level assemblies offer the possibility to infer inversions across species at some detail. In birds, deduction of the process of sex chromosome evolution has been hampered by the lack of a validated chromosome-level assembly from a representative of one of the two basal clades of modern birds, Paleognathae. We therefore developed a high-density genetic linkage map of the ostrich Z chromosome and used this to correct an existing assembly, including correction of a large chimeric superscaffold and the order and orientation of other superscaffolds. We identified the pseudoautosomal region as a 52 Mb segment (≈60% of the Z chromosome) where recombination occurred in both sexes. By comparing the order and location of genes on the ostrich Z chromosome with that of six bird species from the other major clade of birds (Neognathae), and of reptilian outgroup species, 25 Z-linked inversions were inferred in the avian lineages. We defined Z chromosome organization in an early avian ancestor and identified inversions spanning the candidate sex-determining DMRT1 gene in this ancestor, which could potentially have triggered the onset of avian sex chromosome evolution. We conclude that avian sex chromosome evolution has been characterized by a complex process of probably both Z-linked and W-linked inversions (and/or other processes). This study illustrates the need for validated chromosome-level assemblies for inference of genome evolution.
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Affiliation(s)
- Homa Papoli Yazdi
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala, Sweden
| | - Hans Ellegren
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala, Sweden
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Matsubara K, Nishida C, Matsuda Y, Kumazawa Y. Sex chromosome evolution in snakes inferred from divergence patterns of two gametologous genes and chromosome distribution of sex chromosome-linked repetitive sequences. ZOOLOGICAL LETTERS 2016; 2:19. [PMID: 27570632 PMCID: PMC5002183 DOI: 10.1186/s40851-016-0056-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 08/18/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND The discovery of differentially organized sex chromosome systems suggests that heteromorphic sex chromosomes evolved from a pair of homologous chromosomes. Whereas karyotypes are highly conserved in alethinophidian snakes, the degeneration status of the W chromosomes varies among species. The Z and W chromosomes are morphologically homomorphic in henophidian species, whereas in snakes belonging to caenophidian families the W chromosomes are highly degenerated. Snakes therefore are excellent animal models in which to study sex chromosome evolution. Herein, we investigated the differentiation processes for snake sex chromosomes using both coding and repetitive sequences. We analyzed phylogenetic relationships of CTNNB1 and WAC genes, localized to the centromeric and telomeric regions, respectively, of the long arms on snake sex chromosomes, and chromosome distribution of sex chromosome-linked repetitive sequences in several henophidian and caenophidian species. RESULTS Partial or full-length coding sequences of CTNNB1 and WAC were identified for Z homologs of henophidian species from Tropidophiidae, Boidae, Cylindrophiidae, Xenopeltidae, and Pythonidae, and for Z and W homologs of caenophidian species from Acrochordidae, Viperidae, Elapidae, and Colubridae. Female-specific sequences for the two genes were not found in the henophidian (boid and pythonid) species examined. Phylogenetic trees constructed using each gene showed that the Z and W homologs of the caenophidian species cluster separately. The repetitive sequence isolated from the W chromosome heterochromatin of the colubrid Elaphe quadrivirgata and a microsatellite motif (AGAT)8 were strongly hybridized with W chromosomes of the viperid and colubrid species examined. CONCLUSION Our phylogenetic analyses suggest that the cessation of recombination between the Z and W homologs of CTNNB1 and WAC predated the diversification of the caenophidian families. As the repetitive sequences on the W chromosomes were shared among viperid and colubrid species, heterochromatinization of the proto-W chromosome appears to have occurred before the splitting of these two groups. These results collectively suggest that differentiation of the proto-Z and proto-W chromosomes extended to wide regions on the sex chromosomes in the common ancestor of caenophidian families during a relatively short period.
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Affiliation(s)
- Kazumi Matsubara
- Department of Information and Basic Science and Research Center for Biological Diversity, Graduate School of Natural Sciences, Nagoya City University, 1 Yamanohata, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8501 Japan
- Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 Japan
- Current affiliation: Research Center for Bioinformatics and Biosciences, National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa 236-8648 Japan
| | - Chizuko Nishida
- Department of Biological Science, Faculty of Science, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido 060-0810 Japan
| | - Yoichi Matsuda
- Laboratory of Animal Genetics, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 Japan
- Avian Bioscience Research Center, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 Japan
| | - Yoshinori Kumazawa
- Department of Information and Basic Science and Research Center for Biological Diversity, Graduate School of Natural Sciences, Nagoya City University, 1 Yamanohata, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-8501 Japan
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Pinthong K, Tanomtong A, Getlekha N, Sangpadee W, Sangpakdee K, Sanoamuang LO. First Cytogenetic Study of Puff-Faced Water Snake, Homalopsis buccata (Squamata, Colubridae) by Conventional Staining, Ag-NOR Banding and GTG-Banding Techniques. CYTOLOGIA 2013. [DOI: 10.1508/cytologia.78.141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Krit Pinthong
- Biology Program, Faculty of Science and Technology, Surindra Rajabhat University
| | - Alongklod Tanomtong
- Applied Taxonomic Research Center (ATRC), Department of Biology, Faculty of Science, Khon Kaen University
| | - Nuntaporn Getlekha
- Applied Taxonomic Research Center (ATRC), Department of Biology, Faculty of Science, Khon Kaen University
| | - Wiwat Sangpadee
- Biology Program, Faculty of Science, Udon-Thani Rajabhat University
| | | | - La-orsri Sanoamuang
- Applied Taxonomic Research Center (ATRC), Department of Biology, Faculty of Science, Khon Kaen University
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Trajtengertz I, Beçak ML, Ruiz IR. Ribosomal cistrons in Bothrops neuwiedi (Serpentes) subspecies from Brazil. Genome 2012; 38:601-6. [PMID: 18470192 DOI: 10.1139/g95-076] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ribosomal cistrons of six subspecies of Bothrops neuwiedi (Serpentes) were studied at both the cytogenetic and molecular levels. These subspecies populations occur in several Brazilian regions. The analysis of the nucleolar organizing region banding patterns showed variability in the chromosomal localization of rDNA cistrons. The rDNA clusters were found in two microchromosomes, in chromosome pair Number 6, or even in the one homologue of chromosome 6, and one microchromosome, according to the specimen examined but independent of the population from which it was selected. The organization of the rDNA repeat was studied by Southern blot hybridization using Xenopus laevis ribosomal DNA probes. The size of the repeat is 10.4 kilobases (kb), and the intergenic spacer (IGS), 2.6 kb long, is relatively small compared with the size of other vertebrate IGSs. Restriction mapping using the restriction enzymes EcoRI, BamHI, HindIII, and PvuII showed a highly conserved organization of the ribosomal repeats in the total genomic DNA of the subspecies studied.
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Matsubara K, Tarui H, Toriba M, Yamada K, Nishida-Umehara C, Agata K, Matsuda Y. Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes. Proc Natl Acad Sci U S A 2006; 103:18190-5. [PMID: 17110446 PMCID: PMC1838728 DOI: 10.1073/pnas.0605274103] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/23/2006] [Indexed: 11/18/2022] Open
Abstract
All snake species exhibit genetic sex determination with the ZZ/ZW type of sex chromosomes. To investigate the origin and evolution of snake sex chromosomes, we constructed, by FISH, a cytogenetic map of the Japanese four-striped rat snake (Elaphe quadrivirgata) with 109 cDNA clones. Eleven of the 109 clones were localized to the Z chromosome. All human and chicken homologues of the snake Z-linked genes were located on autosomes, suggesting that the sex chromosomes of snakes, mammals, and birds were all derived from different autosomal pairs of the common ancestor. We mapped the 11 Z-linked genes of E. quadrivirgata to chromosomes of two other species, the Burmese python (Python molurus bivittatus) and the habu (Trimeresurus flavoviridis), to investigate the process of W chromosome differentiation. All and 3 of the 11 clones were localized to both the Z and W chromosomes in P. molurus and E. quadrivirgata, respectively, whereas no cDNA clones were mapped to the W chromosome in T. flavoviridis. Comparative mapping revealed that the sex chromosomes are only slightly differentiated in P. molurus, whereas they are fully differentiated in T. flavoviridis, and E. quadrivirgata is at a transitional stage of sex-chromosome differentiation. The differentiation of sex chromosomes was probably initiated from the distal region on the short arm of the protosex chromosome of the common ancestor, and then deletion and heterochromatization progressed on the sex-specific chromosome from the phylogenetically primitive boids to the more advanced viperids.
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Affiliation(s)
- Kazumi Matsubara
- *Laboratory of Animal Cytogenetics, Department of Genome Dynamics, Creative Research Initiative “Sousei” and
| | - Hiroshi Tarui
- Genome Resource and Analysis Subunit, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Michihisa Toriba
- Japan Snake Institute, 3318 Yabuzuka-cho, Ota 379-2301, Japan; and
| | - Kazuhiko Yamada
- *Laboratory of Animal Cytogenetics, Department of Genome Dynamics, Creative Research Initiative “Sousei” and
| | - Chizuko Nishida-Umehara
- *Laboratory of Animal Cytogenetics, Department of Genome Dynamics, Creative Research Initiative “Sousei” and
- Laboratory of Animal Cytogenetics, Division of Life Science, Graduate School of Life Science, Hokkaido University, North 10 West 8, Kita-ku, Sapporo 060-0810, Japan
| | - Kiyokazu Agata
- Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto 606-8502, Japan
| | - Yoichi Matsuda
- *Laboratory of Animal Cytogenetics, Department of Genome Dynamics, Creative Research Initiative “Sousei” and
- Laboratory of Animal Cytogenetics, Division of Life Science, Graduate School of Life Science, Hokkaido University, North 10 West 8, Kita-ku, Sapporo 060-0810, Japan
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Beçak ML, Beçak W, Pereira A. Somatic pairing, endomitosis and chromosome aberrations in snakes (Viperidae and Colubridae). AN ACAD BRAS CIENC 2003; 75:285-300. [PMID: 12947479 DOI: 10.1590/s0001-37652003000300004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The positioning of macrochromosomes of Bothrops jararaca and Bothrops insularis (Viperidae) was studied in undistorted radial metaphases of uncultured cells (spermatogonia and oogonia) not subjected to spindle inhibitors. Colchicinized metaphases from uncultured (spleen and intestine) and cultured tissues (blood) were also analyzed. We report two antagonic non-random chromosome arrangements in untreated premeiotic cells: the parallel configuration with homologue chromosomes associated side by side in the metaphase plate and the antiparallel configuration having homologue chromosomes with antipolar distribution in the metaphase ring. The antiparallel aspect also appeared in colchicinized cells. The spatial chromosome arrangement in both configurations is groupal size-dependent and maintained through meiosis. We also describe, in untreated gonia cells, endomitosis followed by reductional mitosis which restores the diploid number. In B. jararaca males we observed that some gonad regions present changes in the meiotic mechanism. In this case, endoreduplicated cells segregate the diplochromosomes to opposite poles forming directly endoreduplicated second metaphases of meiosis with the suppression of first meiosis. By a successive division, these cells form nuclei with one set of chromosomes. Chromosome doubling in oogonia is known in hybrid species and in parthenogenetic salamanders and lizards. This species also presented chromosome rearrangements leading to aneuploidies in mitosis and meiosis. It is suggested that somatic pairing, endomitosis, meiotic alterations, and chromosomal aberrations can be correlated processes. Similar aspects of nuclei configurations, endomitosis and reductional mitosis were found in other Viperidae and Colubridae species.
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Affiliation(s)
- Maria Luiza Beçak
- Laboratório de Genética, Instituto Butantan, São Paulo, SP, 05503-900, Brasil.
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BECAK W, BECAK ML, NAZARETH HR, OHNO S. CLOSE KARYOLOGICAL KINSHIP BETWEEN THE REPTILIAN SUBORDER SERPENTES AND THE CLASS AVES. Chromosoma 1996; 15:606-17. [PMID: 14333153 DOI: 10.1007/bf00319994] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Iturra P, Veloso A. Further evidence for early sex chromosome differentiation of anuran species. Genetica 1986; 78:25-31. [PMID: 3248710 DOI: 10.1007/bf00058671] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Chromosome banding and meiotic evidence show that XX/XY systems found in two Eupsophus species (Amphibia-Leptodactylidae) represent early stages of sex chromosome differentiation. Pair 14 is heteromorphic in E. migueli males and represents the heterochromosomes. In E. roseus this pair is metacentric and does not show heteromorphism. Paracentromeric constitutive heterochromatin is present in all chromosomes except in the E. migueli and E. roseus metacentric Y chromosomes. Constitutive heterochromatin loss is the structural modification responsible for Y chromosome differentiation. Pericentric inversions may have modified the morphology of the X chromosome of Eupsophus species.
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Affiliation(s)
- P Iturra
- Departamento de Biología Celular y Genética, Facultad de Medicina, Universidad de Chile
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Bianchi NO, Beçak W, De Bianchi MS, Beçak ML, Rabello MN. Chromosome replication in four species of snakes. Chromosoma 1969; 26:188-200. [PMID: 5800664 DOI: 10.1007/bf00326454] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Chapter 4 Cultivation of Tissues and Leukocytes from Amphibians. Methods Cell Biol 1969. [DOI: 10.1016/s0091-679x(08)62115-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Cohen MM, Huang CC, Clark HF. The somatic chromosomes of 3 lizard species: Gekko gecko, Iguana iguana, and Crotaphytus collaris. EXPERIENTIA 1967; 23:769-71. [PMID: 6062904 DOI: 10.1007/bf02154168] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Probable male heterogamety in the deep-sea fish Bathylagus wesethi (Teleostei: Bathylagidae). Chromosoma 1966. [DOI: 10.1007/bf00326446] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
Mitotic figures from the bone marrow of three parthenogenetic species of Cnemidophorus (whiptail lizards) exhibit chromosome numbers in the triploid range. The species are C. velox with 68 chromosomes, C. tesselatus with 69, and C. exsanguis with 70. A fourth parthenogenetic species, C. perplexus, has 46 chromosomes, the same number as the bisexual subspecies C. tigris septentrionalis.
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OHNO S, BECAK W, BECAK ML. X-AUTOSOME RATIO AND THE BEHAVIOR PATTERN OF INDIVIDUAL X-CHROMOSOMES IN PLACENTAL MAMMALS. Chromosoma 1964; 15:14-30. [PMID: 14171167 DOI: 10.1007/bf00326912] [Citation(s) in RCA: 102] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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