That's neat about the migration patterns. I hadn't heard that.
Another thing I think is cool is trying to figure out how/why certain recessive genes survive in the population, when they're obviously deleterious in some way. They would tend to trend to zero, unless they're conferring an advantage that is not immediately obvious, when you only have one copy instead of two. The main example I'm aware of is sickle cell anemia in African blacks: having two recessive genes gives you sickle cell anemia and it's bad, but having only one is protective against malaria. Or at least, that's the theory - I'm not sure how far it's been proven. Similar theories have been advanced for the high incidence of Tay-Sachs disease among Ashkenazi Jews - lethal in its double form, but thought to protect against TB in single copy, so when they were forced into ghettos or camps, with poor living conditions, it would get reinforced. And I just heard recently that someone's proposed that the high incidence of cystic fibrosis genes in those of white European descent (something like 1 in 25 carry it! which is amazing for a gene that until recently killed off those affected before the age of reproduction) may be because having one copy gave you resistance to the Black Death - carriers were more likely to survive. So historical events can shape genetic drift in surprising ways.
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Date: 2007-03-16 07:31 am (UTC)That's neat about the migration patterns. I hadn't heard that.
Another thing I think is cool is trying to figure out how/why certain recessive genes survive in the population, when they're obviously deleterious in some way. They would tend to trend to zero, unless they're conferring an advantage that is not immediately obvious, when you only have one copy instead of two. The main example I'm aware of is sickle cell anemia in African blacks: having two recessive genes gives you sickle cell anemia and it's bad, but having only one is protective against malaria. Or at least, that's the theory - I'm not sure how far it's been proven. Similar theories have been advanced for the high incidence of Tay-Sachs disease among Ashkenazi Jews - lethal in its double form, but thought to protect against TB in single copy, so when they were forced into ghettos or camps, with poor living conditions, it would get reinforced. And I just heard recently that someone's proposed that the high incidence of cystic fibrosis genes in those of white European descent (something like 1 in 25 carry it! which is amazing for a gene that until recently killed off those affected before the age of reproduction) may be because having one copy gave you resistance to the Black Death - carriers were more likely to survive. So historical events can shape genetic drift in surprising ways.