Life

Desidancer and Diana both pointed me to this story about a mixed race couple who gave birth to daughters of very different phenotypes. The explanation in the story is about right, the loci which give you a gestalt impression of racial identity are a tiny sample of your overall genome. In the story it is reported that 7 genes control skin color and F1 (first generation) hybrids should carry half of the variants of each race (since their parents contribute exactly 50% of the genes to each). But the F2 generation can come out as a range of combinations, so it stands to reason that mixed-race couples will have children who vary a great deal in phenotype as the alleles resegregate themselves into alternative combinations. I lay out the details in By the Punnett Square. South Asians, who often exhibit a wide range of color variation from near white to near black, should not be surprised at this sort of dynamic, as the variance within a family can be rather large in complexion.

gnxp.com/blog/2006/02/black-and-white-twins.php