In article <5o2k5s$id2 at nntp3.u.washington.edu>, joe at evolution.genetics.washington.edu (Joe Felsenstein) writes:
>In article <5o1kl5$b4k at dfw-ixnews12.ix.netcom.com>,
>Steven B. Harris <sbharris at ix.netcom.com> wrote:
>>In <33A367BC.4B7E at sprynet.com.ns> Elliot Williams
>><kakapo at sprynet.com.ns> writes:
>>>>>>What is the most common genetic abnormally?
>....
>> About 1 in 20 carries the gene for cystic fibrosis, with the
>>homozygous frequency being about 1 in 4*(20)^2 = 1600.
>>How about lactose intolerance, which is highly frequent in non-European
>populations, and I think about 15% of Europeans are homozygotes for it?
>Me, I'm a heterozygote ...
"Lactose intolerance" is the eurocentric view - it would be more accurate to
describe "lactose tolerance in adults" as the mutant condition, with
(nearly?) all of the carriers being of European descent. It is a bit of a
stretch to describe this as an "abnormality" in any case. Lactose
tolerance is an adaptive trait common in a particular human subpopulation,
as is, oh, darkly pigmented skin. If you are missing this enzyme it isn't
deleterious to your health - unless your only food supply for the winter is
powdered milk!
Regards,
David Mathog
mathog at seqaxp.bio.caltech.edu
Manager, sequence analysis facility, biology division, Caltech
