Sex ratio distortion in bovine sperm correlates to 
recombination in the pseudoautosomal region

A total of 2122 single sperm from 35 bulls belonging to six different paternal half-sib groups were analysed with respect to two markers in the bovine pseudoautosomal region (PAR) and sex- specific loci on the X and Y chromosomes, respectively. A segregation ratio significantly different from 1[ratio ]1 was observed in a test over all families, with a higher proportion of X-bearing gametes (53·5%). The analysis of recombination conducted separately for X- and Y-bearing sperm showed that X-bearing sperm cells possess highly significant individual and between-family variability in recombination rate, whereas Y-bearing sperm show linkage homogeneity. To test whether the two phenomena are related, different logistic regression models were fitted to the data. The results show that sex ratio significantly correlates with changes in recombination rate among X-bearing but not among Y-bearing sperm. Different hypotheses to explain these observations are discussed.

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Battle of the Sex Chromosomes: Competition between X and Y Chromosome-Encoded Proteins for Partner Interaction and Chromatin Occupancy Drives Multicopy Gene Expression and Evolution in Muroid Rodents

Molecular Biology and Evolution ◽

10.1093/molbev/msaa175 ◽

2020 ◽

Vol 37 (12) ◽

pp. 3453-3468 ◽

Cited By ~ 1

Author(s):

Charlotte Moretti ◽

Mélina Blanco ◽

Côme Ialy-Radio ◽

Maria-Elisabetta Serrentino ◽

Clara Gobé ◽

...

Keyword(s):

Gene Expression ◽

Sex Ratio ◽

Sex Chromosomes ◽

Target Genes ◽

Hybrid Sterility ◽

Intragenomic Conflict ◽

Y Chromosomes ◽

Ratio Distortion ◽

Transcriptional Complex ◽

Sex Ratio Distortion

Abstract Transmission distorters (TDs) are genetic elements that favor their own transmission to the detriments of others. Slx/Slxl1 (Sycp3-like-X-linked and Slx-like1) and Sly (Sycp3-like-Y-linked) are TDs, which have been coamplified on the X and Y chromosomes of Mus species. They are involved in an intragenomic conflict in which each favors its own transmission, resulting in sex ratio distortion of the progeny when Slx/Slxl1 versus Sly copy number is unbalanced. They are specifically expressed in male postmeiotic gametes (spermatids) and have opposite effects on gene expression: Sly knockdown leads to the upregulation of hundreds of spermatid-expressed genes, whereas Slx/Slxl1-deficiency downregulates them. When both Slx/Slxl1 and Sly are knocked down, sex ratio distortion and gene deregulation are corrected. Slx/Slxl1 and Sly are, therefore, in competition but the molecular mechanism remains unknown. By comparing their chromatin-binding profiles and protein partners, we show that SLX/SLXL1 and SLY proteins compete for interaction with H3K4me3-reader SSTY1 (Spermiogenesis-specific-transcript-on-the-Y1) at the promoter of thousands of genes to drive their expression, and that the opposite effect they have on gene expression is mediated by different abilities to recruit SMRT/N-Cor transcriptional complex. Their target genes are predominantly spermatid-specific multicopy genes encoded by the sex chromosomes and the autosomal Speer/Takusan. Many of them have coamplified with not only Slx/Slxl1/Sly but also Ssty during muroid rodent evolution. Overall, we identify Ssty as a key element of the X versus Y intragenomic conflict, which may have influenced gene content and hybrid sterility beyond Mus lineage since Ssty amplification on the Y predated that of Slx/Slxl1/Sly.

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Sex Ratios in a Warming World: Thermal Effects on Sex-Biased Survival, Sex Determination, and Sex Reversal

Journal of Heredity ◽

10.1093/jhered/esab006 ◽

2021 ◽

Vol 112 (2) ◽

pp. 155-164

Author(s):

Suzanne Edmands

Keyword(s):

High Temperature ◽

Sex Ratio ◽

Sex Determination ◽

Heat Tolerance ◽

Sex Ratios ◽

Sex Reversal ◽

Survival Sex ◽

Ratio Distortion ◽

Warming World ◽

Sex Ratio Distortion

Abstract Rising global temperatures threaten to disrupt population sex ratios, which can in turn cause mate shortages, reduce population growth and adaptive potential, and increase extinction risk, particularly when ratios are male biased. Sex ratio distortion can then have cascading effects across other species and even ecosystems. Our understanding of the problem is limited by how often studies measure temperature effects in both sexes. To address this, the current review surveyed 194 published studies of heat tolerance, finding that the majority did not even mention the sex of the individuals used, with <10% reporting results for males and females separately. Although the data are incomplete, this review assessed phylogenetic patterns of thermally induced sex ratio bias for 3 different mechanisms: sex-biased heat tolerance, temperature-dependent sex determination (TSD), and temperature-induced sex reversal. For sex-biased heat tolerance, documented examples span a large taxonomic range including arthropods, chordates, protists, and plants. Here, superior heat tolerance is more common in females than males, but the direction of tolerance appears to be phylogenetically fluid, perhaps due to the large number of contributing factors. For TSD, well-documented examples are limited to reptiles, where high temperature usually favors females, and fishes, where high temperature consistently favors males. For temperature-induced sex reversal, unambiguous cases are again limited to vertebrates, and high temperature usually favors males in fishes and amphibians, with mixed effects in reptiles. There is urgent need for further work on the full taxonomic extent of temperature-induced sex ratio distortion, including joint effects of the multiple contributing mechanisms.

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Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽

10.1093/genetics/147.3.1169 ◽

1997 ◽

Vol 147 (3) ◽

pp. 1169-1180 ◽

Cited By ~ 6

Author(s):

Daven C Presgraves ◽

Emily Severance ◽

Gerald S Willrinson

Keyword(s):

Sex Ratio ◽

Sex Chromosome ◽

Sex Ratios ◽

Natural Populations ◽

Meiotic Drive ◽

Operational Sex Ratio ◽

Genetic Modifiers ◽

Ratio Distortion ◽

The Impact ◽

Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

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Color polymorphism and sex ratio distortion in a cichlid fish as an incipient stage in sympatric speciation by sexual selection

Ecology Letters ◽

10.1046/j.1461-0248.1999.00098.x ◽

1999 ◽

Vol 2 (6) ◽

pp. 367-378 ◽

Cited By ~ 117

Author(s):

Seehausen ◽

van Alphen ◽

Lande

Keyword(s):

Sexual Selection ◽

Sex Ratio ◽

Cichlid Fish ◽

Sympatric Speciation ◽

Color Polymorphism ◽

Incipient Stage ◽

Ratio Distortion ◽

Sex Ratio Distortion

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Genetics and Genomics of an Unusual Selfish Sex Ratio Distortion in an Insect

Current Biology ◽

10.1016/j.cub.2018.10.035 ◽

2018 ◽

Vol 28 (23) ◽

pp. 3864-3870.e4 ◽

Cited By ~ 5

Author(s):

Phineas T. Hamilton ◽

Christina N. Hodson ◽

Caitlin I. Curtis ◽

Steve J. Perlman

Keyword(s):

Sex Ratio ◽

Ratio Distortion ◽

Genetics And Genomics ◽

Sex Ratio Distortion

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Molecular Analysis of Insect Meiosis and Sex Ratio Distortion

Springer Series in Experimental Entomology - Molecular Approaches to Fundamental and Applied Entomology ◽

10.1007/978-1-4613-9217-0_10 ◽

1993 ◽

pp. 357-406 ◽

Cited By ~ 3

Author(s):

Terrence W. Lyttle ◽

Chung-I Wu ◽

R. Scott Hawley

Keyword(s):

Sex Ratio ◽

Molecular Analysis ◽

Ratio Distortion ◽

Sex Ratio Distortion

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Photographic polytene chromosome maps for Glossina morsitans submorsitans (Diptera: Glossinidae): cytogenetic analysis of a colony with sex-ratio distortion

Genome ◽

10.1139/g02-057 ◽

2002 ◽

Vol 45 (5) ◽

pp. 871-880 ◽

Cited By ~ 8

Author(s):

A Gariou-Papalexiou ◽

G Yannopoulos ◽

A Zacharopoulou ◽

R H Gooding

Keyword(s):

Sex Ratio ◽

Polytene Chromosome ◽

X Chromosome ◽

Polytene Chromosomes ◽

Glossina Morsitans ◽

Glossina Morsitans Submorsitans ◽

Ratio Distortion ◽

Chromosome Maps ◽

Sex Ratio Distortion ◽

Pharate Adult

Photographic polytene chromosome maps from trichogen cells of pharate adult Glossina morsitans submorsitans were constructed. Using the standard system employed to map polytene chromosomes of Drosophila, the characteristic landmarks were described for the X chromosome and the two autosomes (L1 and L2). Sex-ratio distortion, which is expressed in male G. m. submorsitans, was found to be associated with an X chromosome (XB) that contains three inversions in each arm. Preliminary data indicate no differences in the fecundity of XAXA and XAXB females, but there are indications that G. m. submorsitans in colonies originating from Burkina Faso and Nigeria have genes on the autosomes and (or) the Y chromosome that suppress expression of sex-ratio distortion.Key words: tsetse, Glossina morsitans submorsitans, polytene chromosome maps, inversions, sex-ratio distortion.

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