Data from: The evolutionary dynamics of sexually antagonistic mutations in pseudoautosomal regions of sex chromosomes

Sex chromosomes can evolve gene contents that differ from the rest of the genome, as well as larger sex differences in gene expression compared with autosomes. This probably occurs because fully sex-linked beneficial mutations substitute at different rates from autosomal ones, especially when fitness effects are sexually antagonistic (SA). The evolutionary properties of genes located in the recombining pseudo-autosomal region (PAR) of a sex chromosome have not previously been modelled in detail. Such PAR genes differ from classical sex-linked genes by having two alleles at a locus in both sexes; in contrast to autosomal genes, however, variants can become associated with gender. The evolutionary fates of PAR genes may therefore differ from those of either autosomal or fully sex-linked genes. Here, we model their evolutionary dynamics by deriving expressions for the selective advantages of PAR gene mutations under different conditions. We show that, unless selection is very strong, the probability of invasion of a population by an SA mutation is usually similar to that of an autosomal mutation, unless there is close linkage to the sex-determining region. Most PAR genes should thus evolve similarly to autosomal rather than sex-linked genes, unless recombination is very rare in the PAR.

性染色体可演化出与基因组其余部分存在差异的基因含量，且相较于常染色体，其基因表达的性别差异更为显著。这一现象的潜在成因在于，完全性连锁的有益突变的替代速率与常染色体突变不同，尤其当适合度效应存在性拮抗（sexually antagonistic, SA）时。此前尚无研究对位于性染色体重组型伪常染色体区域（pseudo-autosomal region, PAR）的基因的演化特性开展详细建模。此类伪常染色体区域基因与经典性连锁基因的差异在于，两性的某一基因座上均存在两个等位基因；但与常染色体基因不同的是，其变异可与性别产生关联。因此，伪常染色体区域基因的演化命运可能既不同于常染色体基因，也不同于完全性连锁基因。本文通过推导不同条件下伪常染色体区域基因突变的选择优势表达式，对其演化动力学展开建模。研究表明，除非选择作用极强，否则性拮抗突变入侵种群的概率通常与常染色体突变相近，除非该突变与性别决定区域存在紧密连锁。因此，大多数伪常染色体区域基因的演化模式应更接近常染色体基因，而非性连锁基因，除非伪常染色体区域内的重组事件极为罕见。