| 1. |
- Mank, Judith E, et al.
(författare)
-
Faster-Z evolution is predominantly due to genetic drift.
- 2010
-
Ingår i: Molecular biology and evolution. - 0737-4038 .- 1537-1719. ; 27:3, s. 661-670
-
Tidskriftsartikel (refereegranskat)abstract
- Genes linked to sex chromosomes may show different levels of functional change than autosomal genes due to different evolutionary pressures. We used whole-genome data from zebra finch-chicken orthologs to test for Faster-Z evolution, finding that Z-linked genes evolve up to 50% more rapidly than autosomal genes. We combined these divergence data with information about sex-specific expression patterns in order to determine whether the Faster-Z Effect that we observe was predominantly the result of positive selection of recessive beneficial mutations in the heterogametic sex or primarily due to genetic drift attributable to the lower effective population size of the Z chromosome compared with an autosome. The Faster-Z Effect was no more prevalent for genes expressed predominantly in females; therefore, our data indicate that the largest source of Faster-Z Evolution is the increased levels of genetic drift on the Z chromosome. This is likely a product of sexual selection acting on males, which reduces the effective population size of the Z relative to that of the autosomes. Additionally, this latter result suggests that the relative evolutionary pressures underlying Faster-Z Evolution are different from those in analogous Faster-X Evolution.
|
|
| 2. |
- Mank, Judith E., et al.
(författare)
-
Ontogenetic Complexity of Sexual Dimorphism and Sex-Specific Selection
- 2010
-
Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 27:7, s. 1570-1578
-
Tidskriftsartikel (refereegranskat)abstract
- Sex-biased gene expression is becoming an increasingly important way to study sexual selection at the molecular genetic level. However, little is known about the timing, persistence, and continuity of gene expression required in the creation of distinct male and female phenotypes, and even less about how sex-specific selection pressures shift over the life cycle. Here, we present a time-series global transcription profile for autosomal genes in male and female chicken, beginning with embryonic development and spanning to reproductive maturity, for the gonad. Overall, the amount and magnitude of sex-biased expression increased as a function of age, though sex-biased gene expression was surprisingly ephemeral, with very few genes exhibiting continuous sex bias in both embryonic and adult tissues. Despite a large predicted role of the sex chromosomes in sexual dimorphism, our study indicates that the autosomes house the majority of genes with sex-biased expression. Most interestingly, sex-specific evolutionary pressures shifted over the course of the life cycle, acting equally strongly on female-biased genes and male-biased genes but at different ages. Female-biased genes exhibited high rates of divergence late in embryonic development, shortly before arrested meiosis halts oogenesis. The level of divergence on female-biased late embryonic genes is similar to that seen in male-biased genes expressed in adult gonads, which correlates with the onset of spermatogenesis. These analyses reveal that sex-specific selection pressure varies over the life cycle as a function of male and female biology.
|
|
