Jul 26, 2015

Beyond 2/3 and 1/3: The Complex Signatures of Sex-Biased Admixture on the X Chromosome

Genetics
Amy Goldberg, Noah A Rosenberg

Abstract

Sex-biased demography, in which parameters governing migration and population size differ between females and males, has been studied through comparisons of X chromosomes, which are inherited sex-specifically, and autosomes, which are not. A common form of sex bias in humans is sex-biased admixture, in which at least one of the source populations differs in its proportions of females and males contributing to an admixed population. Studies of sex-biased admixture often examine the mean ancestry for markers on the X chromosome in relation to the autosomes. A simple framework noting that in a population with equally many females and males, two-thirds of X chromosomes appear in females, suggests that the mean X-chromosomal admixture fraction is a linear combination of female and male admixture parameters, with coefficients 2/3 and 1/3, respectively. Extending a mechanistic admixture model to accommodate the X chromosome, we demonstrate that this prediction is not generally true in admixture models, although it holds in the limit for an admixture process occurring as a single event. For a model with constant ongoing admixture, we determine the mean X-chromosomal admixture, comparing admixture on female and male X chromosomes to cor...Continue Reading

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Mentioned in this Paper

Biological Markers
Study
Chromosomes, Human, X
Human Migration
X Chromosome
Factor X
Underpopulation
African American
Radiotherapy Fractionation
Chromosomes

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