scholarly journals Evidence for Increased Levels of Positive and Negative Selection on the X Chromosome versus Autosomes in Humans

2014 ◽  
Vol 31 (9) ◽  
pp. 2267-2282 ◽  
Author(s):  
Krishna R. Veeramah ◽  
Ryan N. Gutenkunst ◽  
August E. Woerner ◽  
Joseph C. Watkins ◽  
Michael F. Hammer
Keyword(s):  
X Chromosome ◽  
Negative Selection ◽  
Chromosome Versus

scholarly journals Codon Usage Bias and Effective Population Sizes on the X Chromosome versus the Autosomes in Drosophila melanogaster

2012 ◽  
Vol 30 (4) ◽  
pp. 811-823 ◽  
Author(s):  
Jose L. Campos ◽  
Kai Zeng ◽  
Darren J. Parker ◽  
Brian Charlesworth ◽  
Penelope R. Haddrill
Keyword(s):  
Drosophila Melanogaster ◽  
Codon Usage ◽  
X Chromosome ◽  
Codon Usage Bias ◽  
Chromosome Versus ◽  
Effective Population ◽  
Population Sizes

scholarly journals Absence of a faster-X effect in beetles (Tribolium, Coleoptera)

2019 ◽  
Author(s):  
Carrie A. Whittle ◽  
Arpita Kulkarni ◽  
Cassandra G. Extavour
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Protein Sequence ◽  
Rapid Evolution ◽  
Sequence Divergence ◽  
Chromosome Versus ◽  
Phenotypic Effect ◽  
Protein Coding ◽  
Protein Coding Genes ◽  
Somatic Tissues

AbstractBackgroundThe faster-X effect, namely the rapid evolution of protein-coding genes on the X-chromosome, has been reported in numerous metazoans. However, the prevalence of this phenomenon across metazoans and its potential causes remain largely unresolved. Analysis of sex-biased genes may elucidate its possible mechanisms: a more pronounced faster-X effect in male-biased genes than in female-biased or unbiased genes, suggests fixation of recessive beneficial mutations rather than genetic drift. Further, theory predicts that the faster-X effect should be promoted by X-chromosome dosage compensation, but this topic remains rarely empirically examined.ResultsHere, we asked whether we could detect a faster-X effect in genes of the beetle Tribolium castaneum (and T. freemani orthologs), which has X/Y sex-determination and heterogametic males. Our comparison of protein sequence divergence (dN/dS) on the X-chromosome versus autosomes indicated the complete absence of a faster-X effect. Further, analyses of sex-biased gene expression revealed that the X-chromosome was strongly enriched for ovary-biased genes, which evolved under exceptionally high constraint. An evaluation of male X-chromosome dosage compensation in the gonads and in non-gonadal somatic tissues showed an extreme lack of compensation in the testis. This under-expression of the X chromosome in males may limit the phenotypic effect, and therefore likelihood of fixation, of recessive beneficial X-linked mutations in genes transcribed in male gonads.ConclusionsWe show that these beetles display a rare unequivocal example of the absence of a faster-X effect in a metazoan. We propose two potential causes for this, namely high constraint on X-linked ovary-biased genes, and an extreme lack of dosage compensation of genes transcribed in the testis.

X-linked CNV and skewed X-chromosome inactivation

2020 ◽  
pp. 19-21
Author(s):  
Е.А. Фонова ◽  
Е.Н. Толмачева ◽  
А.А. Кашеварова ◽  
М.Е. Лопаткина ◽  
К.А. Павлова ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Intellectual Disability ◽  
X Chromosome ◽  
Copy Number ◽  
Copy Number Variations ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
Chromosome X ◽  
Skewed X Chromosome Inactivation

Смещение инактивации Х-хромосомы может быть следствием и маркером нарушения клеточной пролиферации при вариациях числа копий ДНК на Х-хромосоме. Х-сцепленные CNV выявляются как у женщин с невынашиванием беременности и смещением инактивации Х-хромосомы (с частотой 33,3%), так и у пациентов с умственной отсталостью и смещением инактивацией у их матерей (с частотой 40%). A skewed X-chromosome inactivation can be a consequence and a marker of impaired cell proliferation in the presence of copy number variations (CNV) on the X chromosome. X-linked CNVs are detected in women with miscarriages and a skewed X-chromosome inactivation (with a frequency of 33.3%), as well as in patients with intellectual disability and skewed X-chromosome inactivation in their mothers (with a frequency of 40%).

Sign in / Sign up

Export Citation Format

Share Document