It was theorised in 1984 that sexually antagonistic genetic (SA) variation should more easily evolve on the X-chromosome. This is partly because female beneficial/male deleterious mutations face less powerful selection against them; the X is in females twice as often as in males so mutations will persist up to the point where male cost is <2x the females gain. Furthermore, male beneficial/female deleterious recessive mutations (p) will always be expressed in males and, when rare, only very occasionally in females; if the frequency of p 0.1 then 1 in 10 males will express that trait and only 1 in 100 of the females.

It is therefore expected that the X-chromosome should become a hotspot for SA variation in comparison to the autosomes. A result would be increased persistence of genetic variation on the X- within sexually antagonistic loci. However, how would a sexually concordant (male & female beneficial, or male & female deleterious) fare in the X- compared to the autosomes? Just eyeballing it, it feels like the X- should be better able to select on recessive mutations because they are always expressed in males; removing deleterious and spreading beneficial mutations more rapidly. Should there then be less genetic variation on the X- than autosomes?

  • $\begingroup$ I dont really understand what Sexual Antagonism means. However this article may be relevant to your question. Just happened to see it some days back. $\endgroup$ – WYSIWYG Aug 30 '14 at 9:25
  • $\begingroup$ @WYSIWYG - I briefly touch on sexual antagonism in my answer to this question. See the last part where I talk about conflict. $\endgroup$ – Michael S Taylor Aug 31 '14 at 13:31

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