Sex-limited genes
From The Art and Popular Culture Encyclopedia
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Sex-limited genes are genes which are present in both sexes of sexually reproducing species but expressed in only one sex. In other words, sex-limited genes cause the two sexes to show different traits or phenotypes. Strictly, this term is restricted to autosomal traits, to distinguish them from sex-linked characteristics. An example of sex-limited genes are genes which instructs male elephant seal to grow big and fight, at the same time instructing female seals to grow small and avoid fights. These genes are responsible for sexual dimorphism.
Epigenetics
Epigenetics is the inheritance of additional marks to the genome without changes in its sequence. These factors epigenetic factors may also be sex-limited. Genomic imprinting for example, silencing of one parental allele by DNA methylation, for which sex-limited imprinting has been proposed to resolve intralocus conflict. Genomic imprinting has been shown to be indistinguishable from non-imprinted systems at the population level in some cases, having equivalent evolutionary models. However, this does not hold for sex-limited models of sex-limited imprinting which behave differently depending on which sex imprinting occurs and the parental sex of imprinted allele. Specifically, this affects whether alleles are imprinted in consecutive generations with different evolutionary trajectories (under the same selection fitnesses) arising purely due to sex-limited epigenetics. Thus sex-limited epigenetic traits may have played a pivotal role in the evolution of mammals and other species, particularly as a mechanism to ameliorate intralocus conflict between the sexes.
