Do you think dragon riding genetic, like X-chromosome linked or Autosomal recessive? Do you think Septon Barth a reference to Mendel and Barth syndrome, an x chromosome disorder?

It’s definitely genetic – hence the dragonseeds, the Valyrian emphasis on incest to maintain the gift, etc. etc. I don’t think it’s X-chromosome linked, because you’d see fewer women than men being dragonriders and that doesn’t seem to be the case.