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EMBARGO: September 22nd, 2016 11 AM Pacific / 2 PM Eastern Time
Genome-wide study quantifies genetic “war between the sexes”
Humans and flies are still undergoing natural selection based on sex
Genes with moderately different expression levels in males and
females are subject to ongoing, sex-related natural selection,
reports a new study by Changde Cheng and Mark Kirkpatrick at the
University of Texas, Austin, published September 22nd, 2016 in
PLOS Genetics.
Differences between males and females—whether humans or
flies—come from differences in gene expression in the sexes, but
exactly how evolution has shaped those differences is still a
mystery. Scientists quantified the relationship between sex-biased
expression, which are variations in gene expression between the
sexes, and sex-specific selection, which is when natural selection favors different traits in different sexes, on a
genome-wide scale in humans and flies. They observe a “Twin Peaks” pattern in both species where genes with
intermediate differences in expression between the sexes are undergoing the greatest level of sex-specific
selection, while genes that are either completely or not at all expressed differently undergo little selection. The
pattern suggests that the “war between the sexes” is more than a metaphor: it contributes to measurable
patterns in genes that affect mortality in humans.
The study’s results suggest that ongoing sex-specific selection commonly occurs in the genomes of humans and
flies. These findings help inform our understanding of how differences between the sexes evolve, and factors
affecting the evolution of entire genomes.
Kirkpatrick says "In the last few years, human genetics has been revolutionized by the discovery of evidence for
widespread and recent adaptive evolution across the human genome. This study brings that picture into real
time: we now see evidence for selection on many genes working within the lifetimes of living individuals. Further,
the type of selection involves gene variants (alleles) that improve survival in one sex while decreasing it in the
other. What is good genetically for females is bad for males, and vice versa.”
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In your coverage please use this URL to provide access to the freely available article in PLOS Genetics:
http://dx.doi.org/10.1371/journal.pgen.1006170
Press-only preview: http://plos.io/2cCiKka
Contact: Mark Kirkpatrick ([email protected])
Image Caption: The strength of sex-specific selection is strongest on human autosomal genes with intermediate
sex-biased expression.
The white curve is the best-fit 4th degree polynomial and the intensity of red indicates the likelihood that the
regression passes through a given value. The average FST for the SNPs in a gene is small at Δ = 0 (unbiased
expression), increases to a peak as sex-bias grows, then decreases as Δ approaches –1 and 1. The numbers of
genes with a given bias are visualized in the density plot in the lower part of the figure; dark gray denotes
intermediate sex-biased expression.
Image Credit: Cheng et al, 2016
Citation: Cheng C, Kirkpatrick M (2016) Sex-Specific Selection and Sex-Biased Gene Expression in Humans and
Flies. PLoS Genet 12(9): e1006170. doi:10.1371/journal.pgen.1006170
Funding: This work was supported by the Swiss National Science Foundation
(http://www.snf.ch/en/funding/programmes/sinergia/Pages/default.aspx) (Grant CRSII3-147625 to MK). The
funders had no role in study design, data collection and analysis, decision to publish, or preparation of the
manuscript.
Competing Interests: The authors have declared that no competing interests exist.
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