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Ruiz-Herrera A, Waters PD. Fragile, unfaithful and persistent Ys-on how meiosis can shape sex chromosome evolution. Heredity (Edinb) 2022; 129:22-30. [PMID: 35459933 PMCID: PMC9273583 DOI: 10.1038/s41437-022-00532-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 03/27/2022] [Accepted: 03/28/2022] [Indexed: 12/28/2022] Open
Abstract
Sex-linked inheritance is a stark exception to Mendel's Laws of Heredity. Here we discuss how the evolution of heteromorphic sex chromosomes (mainly the Y) has been shaped by the intricacies of the meiotic programme. We propose that persistence of Y chromosomes in distantly related mammalian phylogroups can be explained in the context of pseudoautosomal region (PAR) size, meiotic pairing strategies, and the presence of Y-borne executioner genes that regulate meiotic sex chromosome inactivation. We hypothesise that variation in PAR size can be an important driver for the evolution of recombination frequencies genome wide, imposing constraints on Y fate. If small PAR size compromises XY segregation during male meiosis, the stress of producing aneuploid gametes could drive function away from the Y (i.e., a fragile Y). The Y chromosome can avoid fragility either by acquiring an achiasmatic meiotic XY pairing strategy to reduce aneuploid gamete production, or gain meiotic executioner protection (a persistent Y). Persistent Ys will then be under strong pressure to maintain high recombination rates in the PAR (and subsequently genome wide), as improper segregation has fatal consequences for germ cells. In the event that executioner protection is lost, the Y chromosome can be maintained in the population by either PAR rejuvenation (extension by addition of autosome material) or gaining achiasmatic meiotic pairing, the alternative is Y loss. Under this dynamic cyclic evolutionary scenario, understanding the meiotic programme in vertebrate and invertebrate species will be crucial to further understand the plasticity of the rise and fall of heteromorphic sex chromosomes.
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Affiliation(s)
- Aurora Ruiz-Herrera
- Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina (IBB), Universitat Autònoma de Barcelona (UAB), Cerdanyola del Vallès, 08193, Spain.
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona (UAB), Cerdanyola del Vallès, 08193, Spain.
| | - Paul D Waters
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW Sydney, Sydney, NSW, 2052, Australia.
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2
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The synaptonemal complex imposes crossover interference and heterochiasmy in Arabidopsis. Proc Natl Acad Sci U S A 2021; 118:2023613118. [PMID: 33723072 PMCID: PMC8000504 DOI: 10.1073/pnas.2023613118] [Citation(s) in RCA: 89] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Meiotic recombination promotes genetic diversity by shuffling parental chromosomes. As observed by the very first geneticists, crossovers inhibit the formation of another crossover nearby, an elusive phenomenon called crossover interference. Another intriguing observation is heterochiasmy, the marked difference in male and female crossover rates observed in many species. Here, we show that the synaptonemal complex, a structure that zips homologous chromosomes together during meiosis, is essential for crossover interference in Arabidopsis. This suggests that a signal that inhibits crossover formation nearby a first crossover propagates along this specific structure. Furthermore, in the absence of the synaptonemal complex, crossover frequencies become identical in both sexes, suggesting that heterochiasmy is due to variation of crossover interference imposed by the synaptonemal complex. Meiotic crossovers (COs) have intriguing patterning properties, including CO interference, the tendency of COs to be well-spaced along chromosomes, and heterochiasmy, the marked difference in male and female CO rates. During meiosis, transverse filaments transiently associate the axes of homologous chromosomes, a process called synapsis that is essential for CO formation in many eukaryotes. Here, we describe the spatial organization of the transverse filaments in Arabidopsis (ZYP1) and show it to be evolutionary conserved. We show that in the absence of ZYP1 (zyp1a zyp1b null mutants), chromosomes associate in pairs but do not synapse. Unexpectedly, in absence of ZYP1, CO formation is not prevented but increased. Furthermore, genome-wide analysis of recombination revealed that CO interference is abolished, with the frequent observation of close COs. In addition, heterochiasmy was erased, with identical CO rates in males and females. This shows that the tripartite synaptonemal complex is dispensable for CO formation and has a key role in regulating their number and distribution, imposing CO interference and heterochiasmy.
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Koul KK, Nagpal R, Nain K. Male and female meiosis evince differential patterns in chiasma formation: a case study of ornamental plant, Delphinium ajacis L. J Genet 2020. [DOI: 10.1007/s12041-020-1179-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Palmer N, Talib SZA, Singh P, Goh CMF, Liu K, Schimenti JC, Kaldis P. A novel function for CDK2 activity at meiotic crossover sites. PLoS Biol 2020; 18:e3000903. [PMID: 33075054 PMCID: PMC7595640 DOI: 10.1371/journal.pbio.3000903] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 10/29/2020] [Accepted: 09/14/2020] [Indexed: 12/23/2022] Open
Abstract
Genetic diversity in offspring is induced by meiotic recombination, which is initiated between homologs at >200 sites originating from meiotic double-strand breaks (DSBs). Of this initial pool, only 1-2 DSBs per homolog pair will be designated to form meiotic crossovers (COs), where reciprocal genetic exchange occurs between parental chromosomes. Cyclin-dependent kinase 2 (CDK2) is known to localize to so-called "late recombination nodules" (LRNs) marking incipient CO sites. However, the role of CDK2 kinase activity in the process of CO formation remains uncertain. Here, we describe the phenotype of 2 Cdk2 point mutants with elevated or decreased activity, respectively. Elevated CDK2 activity was associated with increased numbers of LRN-associated proteins, including CDK2 itself and the MutL homolog 1 (MLH1) component of the MutLγ complex, but did not lead to increased numbers of COs. In contrast, reduced CDK2 activity leads to the complete absence of CO formation during meiotic prophase I. Our data suggest an important role for CDK2 in regulating MLH1 focus numbers and that the activity of this kinase is a key regulatory factor in the formation of meiotic COs.
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Affiliation(s)
- Nathan Palmer
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology, and Research), Singapore, Republic of Singapore
- Department of Biochemistry, National University of Singapore (NUS), Singapore, Republic of Singapore
| | - S. Zakiah A. Talib
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology, and Research), Singapore, Republic of Singapore
| | - Priti Singh
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Christine M. F. Goh
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology, and Research), Singapore, Republic of Singapore
| | - Kui Liu
- Department of Obstetrics and Gynecology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Shenzhen Key Laboratory of Fertility Regulation, Center of Assisted Reproduction and Embryology, The University of Hong Kong—Shenzhen Hospital, Shenzhen, China
| | - John C. Schimenti
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Philipp Kaldis
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology, and Research), Singapore, Republic of Singapore
- Department of Biochemistry, National University of Singapore (NUS), Singapore, Republic of Singapore
- Department of Clinical Sciences, Clinical Research Centre, Lund University, Malmö, Sweden
- * E-mail:
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Giraut L, Falque M, Drouaud J, Pereira L, Martin OC, Mézard C. Genome-wide crossover distribution in Arabidopsis thaliana meiosis reveals sex-specific patterns along chromosomes. PLoS Genet 2011; 7:e1002354. [PMID: 22072983 PMCID: PMC3207851 DOI: 10.1371/journal.pgen.1002354] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Accepted: 09/08/2011] [Indexed: 11/19/2022] Open
Abstract
In most species, crossovers (COs) are essential for the accurate segregation of homologous chromosomes at the first meiotic division. Their number and location are tightly regulated. Here, we report a detailed, genome-wide characterization of the rate and localization of COs in Arabidopsis thaliana, in male and female meiosis. We observed dramatic differences between male and female meiosis which included: (i) genetic map length; 575 cM versus 332 cM respectively; (ii) CO distribution patterns: male CO rates were very high at both ends of each chromosome, whereas female CO rates were very low; (iii) correlations between CO rates and various chromosome features: female CO rates correlated strongly and negatively with GC content and gene density but positively with transposable elements (TEs) density, whereas male CO rates correlated positively with the CpG ratio. However, except for CpG, the correlations could be explained by the unequal repartition of these sequences along the Arabidopsis chromosome. For both male and female meiosis, the number of COs per chromosome correlates with chromosome size expressed either in base pairs or as synaptonemal complex length. Finally, we show that interference modulates the CO distribution both in male and female meiosis.
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Affiliation(s)
- Laurène Giraut
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Versailles, France
| | - Matthieu Falque
- UMR de Génétique Végétale du Moulon, INRA/CNRS/Univ Paris-Sud/AgroParisTech, Gif sur Yvette, France
| | - Jan Drouaud
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Versailles, France
| | - Lucie Pereira
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Versailles, France
| | - Olivier C. Martin
- UMR de Génétique Végétale du Moulon, INRA/CNRS/Univ Paris-Sud/AgroParisTech, Gif sur Yvette, France
| | - Christine Mézard
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Versailles, France
- * E-mail:
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Drouaud J, Mercier R, Chelysheva L, Bérard A, Falque M, Martin O, Zanni V, Brunel D, Mézard C. Sex-specific crossover distributions and variations in interference level along Arabidopsis thaliana chromosome 4. PLoS Genet 2007; 3:e106. [PMID: 17604455 PMCID: PMC1904369 DOI: 10.1371/journal.pgen.0030106] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 05/14/2007] [Indexed: 11/25/2022] Open
Abstract
In many species, sex-related differences in crossover (CO) rates have been described at chromosomal and regional levels. In this study, we determined the CO distribution along the entire Arabidopsis thaliana Chromosome 4 (18 Mb) in male and female meiosis, using high density genetic maps built on large backcross populations (44 markers, >1,300 plants). We observed dramatic differences between male and female map lengths that were calculated as 88 cM and 52 cM, respectively. This difference is remarkably parallel to that between the total synaptonemal complex lengths measured in male and female meiocytes by immunolabeling of ZYP1 (a component of the synaptonemal complex). Moreover, CO landscapes were clearly different: in particular, at both ends of the map, male CO rates were higher (up to 4-fold the mean value), whereas female CO rates were equal or even below the chromosomal average. This unique material gave us the opportunity to perform a detailed analysis of CO interference on Chromosome 4 in male and female meiosis. The number of COs per chromosome and the distances between them clearly departs from randomness. Strikingly, the interference level (measured by coincidence) varied significantly along the chromosome in male meiosis and was correlated to the physical distance between COs. The significance of this finding on the relevance of current CO interference models is discussed. Meiotic crossovers between homologous chromosomes ensure their proper segregation to generate ultimately gametes. They also create new allelic combinations which contribute to the diversity of traits among individuals. In all eukaryotes, the number and the localization of crossovers along chromosomes are not random. In addition, crossovers are not independent of each other: the occurrence of a crossover lowers the probability that another crossover arises in its vicinity. The mechanism of this phenomenon, called “crossover interference,” is one of the most challenging puzzles that geneticists have been faced with in the last century. In this paper, we precisely described the distribution of crossovers along Chromosome 4 of the model plant species Arabidopsis thaliana, separately in male and female meiosis. Interestingly, we observed that crossovers are 1.7 more numerous in male than in female meiosis, and this increase is especially marked at the ends of the chromosome. Moreover, our results provide the first evidence that the level of interference along a chromosome is not a constant and is correlated with the physical distance between crossovers. These results shed new light on the determinism of crossover localization and could have important outcomes on the relevance of current models of crossover interference.
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Affiliation(s)
- Jan Drouaud
- Station de Génétique et d'Amélioration des Plantes, Institut Jean Pierre Bourgin, INRA, Versailles, France
| | - Raphaël Mercier
- Station de Génétique et d'Amélioration des Plantes, Institut Jean Pierre Bourgin, INRA, Versailles, France
| | - Liudmila Chelysheva
- Station de Génétique et d'Amélioration des Plantes, Institut Jean Pierre Bourgin, INRA, Versailles, France
| | - Aurélie Bérard
- UR Etude du Polymorphisme des Génomes Végétaux, Centre National de Génotypage, Evry, France
| | - Matthieu Falque
- UMR de Génétique Végétale, INRA, Université Paris-Sud, CNRS, Institut National Agronomique Paris-Grignon, Gif-sur-Yvette, France
| | - Olivier Martin
- UMR de Génétique Végétale, INRA, Université Paris-Sud, CNRS, Institut National Agronomique Paris-Grignon, Gif-sur-Yvette, France
- Laboratoire de Physique Théorique et Modèles Statistiques, Université Paris-Sud, Orsay, France
| | - Vanessa Zanni
- Station de Génétique et d'Amélioration des Plantes, Institut Jean Pierre Bourgin, INRA, Versailles, France
| | - Dominique Brunel
- UR Etude du Polymorphisme des Génomes Végétaux, Centre National de Génotypage, Evry, France
| | - Christine Mézard
- Station de Génétique et d'Amélioration des Plantes, Institut Jean Pierre Bourgin, INRA, Versailles, France
- * To whom correspondence should be addressed. E-mail:
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Zhang L, Murray BG, Pickering RA. Variable patterns of chromosome synapsis at pachytene in Hordeum vulgare x H. bulbosum hybrids and their parents. Hereditas 2003; 137:90-5. [PMID: 12627832 DOI: 10.1034/j.1601-5223.2002.01549.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Synaptonemal complexes (SC) have been analysed in barley (Hordeum vulgare), H. bulbosum and two F, hybrids between them. These hybrids show different recombination frequencies and at pachytene show significant differences in the total length of SC formed and in the extent of synapsis. Higher recombination frequency in the hybrids was correlated with a greater total SC length. Differences in SC length were also observed between the parental species with H. bulbosum having a greater SC length than H. vulgare. However, species and hybrid can have similar SC lengths but clearly different recombination frequencies and, therefore, the relationship between SC length and recombination is not clear-cut.
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Affiliation(s)
- Liangtao Zhang
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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Cuñado N, Terrones J, Sánchez L, Martínez P, Santos JL. Sex-dependent synaptic behaviour in triploid turbot, Scophthalmus maximus (Pisces, Scophthalmidae). Heredity (Edinb) 2002; 89:460-4. [PMID: 12466989 DOI: 10.1038/sj.hdy.6800165] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2001] [Accepted: 07/10/2002] [Indexed: 11/10/2022] Open
Abstract
A surface-spreading synaptonemal complex (SC) technique was used to analyse spermatocytes and oocytes of triploid turbot (Scophthalmus maximus) in order to visualise the process of chromosome synapsis. The most conspicuous characteristic of triploid oocytes is that, in the trivalents, the lateral elements of the SC were frequently associated in threes, either completely along the length of the trivalent, or partially, forming a variety of forked structures. In these nuclei, synapsis usually occurred among homologous chromosomes and the number of bivalents observed was significantly higher than that expected under the assumption of random chromosome association among all partners. However, the frequency of trivalents was very low in triploid spermatocytes, triple synapsis being also scarce. In these nuclei chromosomes that were excluded from homologous synapsis become engaged in random SC formation, and, therefore a considerable number of non-homologous associations are produced. The causes of the synaptic differences observed in triploid males and females of turbot and their possible relation to the sterility displayed by these animals are discussed.
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Affiliation(s)
- N Cuñado
- Departamento de Genética, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain
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Abstract
Meiotic chromosomes have been studied for many years, in part because of the fundamental life processes they represent, but also because meiosis involves the formation of homolog pairs, a feature which greatly facilitates the study of chromosome behavior. The complex events involved in homolog juxtaposition necessitate prolongation of prophase, thus permitting resolution of events that are temporally compressed in the mitotic cycle. Furthermore, once homologs are paired, the chromosomes are connected by a specific structure: the synaptonemal complex. Finally, interaction of homologs includes recombination at the DNA level, which is intimately linked to structural features of the chromosomes. In consequence, recombination-related events report on diverse aspects of chromosome morphogenesis, notably relationships between sisters, development of axial structure, and variations in chromatin status. The current article reviews recent information on these topics in an historical context. This juxtaposition has suggested new relationships between structure and function. Additional issues were addressed in a previous chapter (551).
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Affiliation(s)
- D Zickler
- Institut de Génétique et Microbiologie, Université Paris-Sud, Orsay, France.
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Carrasco LA, Penman DJ, Villalobos SA, Bromage N. The effects of oral administration with 17 alpha-methyltestosterone on chromosomal synapsis in Oreochromis niloticus (Pisces, Cichlidae). Mutat Res 1999; 430:87-98. [PMID: 10592320 DOI: 10.1016/s0027-5107(99)00152-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The pattern of chromosomal synapsis after treatment with 17 alpha-methyltestosterone (MT), a testosterone analogue routinely used for the reversal of phenotypic sex in aquaculture, was investigated using the Nile tilapia (Oreochromis niloticus) as a model teleost species. Progeny-tested, monosex diploid (2n = 44) individuals were orally administered with diets containing 50 mg/kg MT for 30 days after first feeding (XX(MT) neomales and XY(MT) males) and compared to controls (XY males). The formation and structure of the synaptonemal complex (SC) and the nature of chromosomal synapsis were investigated in control and treated groups by computer-assisted image analysis of transmission electron microscope (TEM) microphotographs taken from SC spreads. Nuclei at the pachytene stage were first observed in XX(MT) neomales, indicating an earlier commitment of genetically female spermatocytes to enter the first meiotic prophase. Administration of MT did not result in obvious SC lesions, breakage, asynapsis or formation of multivalents in genotypic females (XX(MT) neomales). Administration of MT resulted in a significant increase in the SC lengths in XY(MT) males, although it did not significantly alter the pattern of synapsis (SC structure and number and morphology of bivalents) in comparison to XY controls. The significance of the effects and the putative mode(s) of action of MT on chromosomal synapsis in teleosts is discussed.
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Affiliation(s)
- L A Carrasco
- Genetics and Reproduction Research Group, Institute of Aquaculture, University of Stirling, Scotland FK9 4LA, UK.
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11
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Santos JL. The relationship between synapsis and recombination: two different views. Heredity (Edinb) 1999. [DOI: 10.1038/sj.hdy.6884870] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Quevedo C, Cerro ALD, Santos JL, Jones GH. Correlated variation of chiasma frequency and synaptonemal complex length in Locusta migratoria. Heredity (Edinb) 1997. [DOI: 10.1038/hdy.1997.80] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Abstract
The longest chromosome (number 1) of Trituturus cristatus carries a heteromorphic segment, a heterozygosity perpetuated by a balanced lethal system. The heteromorphic segment is regarded as achiasmate and has been claimed to be asynaptic. Direct observations of chromosome pairing in spermatocytes and oocytes yield some cases where all homologous chromosomes appear to be completely paired, but the individual bivalents could not be identified as pachytene is not particularly clear in this species. The long arms of bivalent 1 usually remain attached by a terminal chiasma in spermatocytes of T. c. cristatus but the corresponding chiasma is only rarely present in T. c. carnifex spermatocytes. Synaptonemal complexes have been measured in both spermatocytes and oocytes of T. c. cristatus. A karyotype constructed from these measurements matches the main features of somatic and lampbrush chromosome karyotypes, indicating that all chromosomes must be completely paired and proportionately represented as synaptonemal complex. The total length of synaptonemal complex is much the same in spermatocytes and oocytes and is similar to the length in spermatocytes of Xenopus laevis. These two amphibian examples supplement a recent survey of other vertebrate classes to reinforce its conclusion that synaptonemal complex length is not related to genome size in vertebrates.Key words: chromosome pairing, synaptonemal complex, genome size, amphibia.
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14
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Jiménez G, Jenkins G. Lateral element lengths and nuclear disposition in Lolium. Heredity (Edinb) 1995. [DOI: 10.1038/hdy.1995.135] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Peterson DG, Stack SM, Healy JL, Donohoe BS, Anderson LK. The relationship between synaptonemal complex length and genome size in four vertebrate classes (Osteicthyes, Reptilia, Aves, Mammalia). Chromosome Res 1994; 2:153-62. [PMID: 8032674 DOI: 10.1007/bf01553494] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We investigated the relationship between synaptonemal complex (SC) length and genome size in 18 species of vertebrates from the classes Osteicthyes (bony fish), Reptilia (reptiles), Aves (birds), and Mammalia (mammals). When total SC length was plotted against genome size for all 18 vertebrate species, there did not appear to be a correlation between the two variables. However, when birds were excluded from the data and a linear regression analysis was performed, variation in genome size accounted for approximately 50% of the variation in total SC length (r2 = 0.47). Dividing the average total SC length for a species by its 4C DNA amount yields the species' SC/DNA ratio. SC/DNA ratios of birds were approximately twice as high as the SC/DNA ratios of reptiles and mammals. Bony fish showed intraclass divergence in SC/DNA ratios. The sunfish (Centrarchidae) had SC/DNA ratios almost as high as those of birds, while the remaining fish in the study had SC/DNA ratios similar to those of reptiles and mammals. These observations indicate that inter and intraclass divergence in the relationship between total SC length and genome size has occurred in the vertebrates. Coupled with evidence from the literature, our results also suggest that SC/DNA ratios are positively correlated with crossover frequency.
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Affiliation(s)
- D G Peterson
- Department of Biology, Colorado State University, Fort Collins 80523
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De Azkue D, Jones GH. Inter- and intra-plant SC length variation in Crepis capillaris. Heredity (Edinb) 1993. [DOI: 10.1038/hdy.1993.150] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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17
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Evidence of a joint control of chiasma formation in spermatocytes and oocytes of a grasshopper. Heredity (Edinb) 1990. [DOI: 10.1038/hdy.1990.112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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