XX XY happen as usual mostly in science books.
My mind tends to veer of slightly off topic nearly all the time. You will have to forgive me again.
Lorenzo L Pesce

XX and XY was what kids in middle school learned a generation ago before we entered the era of bioinformatics. Genome, human and otherwise, are complex beyond belief. I reference a post I made about this elsewhere, http://virginiahall.net/post/149225182377/is-god-a-wad-of-dna

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