shady genetics musings

isn't it cute? vivid example of genetic mosaicism, maybe? Her mom is a horse and her dad is a zebra. My guess is that her patches of zebra coat and patches of pure white coat are due to an early recombination event in the paternal gamete: the autosomal chromosome carrying the gene for stripes traded a chunk of genome with the X chromosome, so the stripey gene ended up on the paternal X. Since females have two X's where males have one X, female mammals compensate by only expressing one of the X chromosomes; thus male and female mammals have the same level of sex chomosome expression. The result is that some cells express only the maternal X chromosome which doesn't have the stripey gene, and some cells express only the paternal X chromosome(which after recombination carries the autosomal stripey gene). That could be why this girl has obviously different patches of coat, instead of a uniform coat that blended the characteristics. Mosaicism can only occur in female mammals, not males: if this individual were a boy, it would probably have a uniform zebra pattern, though maybe lighter than usual. Also, ALL females (including human women) exhibit mosaicism because of sex chromosome dosage compensation! Neat eh?

** Was confused earlier about when the recombination took place, but the simple answer turns out to be that it takes place in the father's gametes, NOT with the mother's X chromosome. Silly me.