Hair color is about as non-Mendelian as you can get, meaning that it doesn't follow simple dominant/recessive patterns and it's carried on a number of separate genes (polygenic trait). If I understand the nuances of protein synthesis correctly (and I'm pretty sure I do), there is no specific gene for blond hair. There are a number of sites on an individual's DNA, called "loci" (singular "locus"), that code for the production of a given hair pigment. If one of these loci holds the allele (code sequence) for the production of one of these pigments, that locus will produce the pigment. The more alleles one has to produce hair pigments, the darker his or her hair will be. There are at least two types of pigments, one for brown color and one for red (I forget the name for the red pigment; I think the brown pigment is melanin, the same as is produced in skin). Blonds don't have a specific blond allele, they just lack several pigment-production ones. In the situation described by perldude, the "recessive" alleles carried by the Norwegian blond would stay in circulation, so to speak, until they disappeared due to an event known as "genetic drift," which I won't bore you by describing. More than likely, the heavy concentration of pigment genes among the Africans would keep the blond's alleles from showing up.
I hope this clears things up. |
