🚀 go-pugleaf

In article <10276@ut-emx.UUCP> ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:
>Not being a geneticist, I have frequently wondered, but never looked into,
>the question of why an infrequent mutation like Tay-Sachs, which has such
>a devastating effect on those unfortunates who are homozygous for it, has
>such a relatively *high* incidence among Ashkenzaic Jewry (I believe that
>1/30 individuals is heterozygous).  The obvious
>answer would be that being heterozygous for it is good in some way. 
>Has anyone ever found anything it might be good for?  I suppose a
>tolerance for kosher wine would fit with the data (from extensive
>personal experience I know that I lack that trait), but are there any
>serious answers?

I have heard of two possible explanations for the high frequency of T-S in
Ashkenazy Jews.  The first is random drift.  Because of the relatively high
inbreeding among this group (as least when they were developing as a group)
it is possible that the high frequency arose through random sampling.  The
second has been proposed by Jared Diamond.  In this explanation, the
heterozygote is supposed to confer resistance to TB.  This particular group
was one of the few successful groups of people to populate cities of Europe
in the Middle Ages (where selection was quite severe).  TB was particularly
common in cities at the time.  I do not know of direct evidence for his
theory, and when he gave a talk here a couple of years ago he did not have
any solid "proof".


-- 
Ted H. Emigh, Dept. Genetics and Statistics, NCSU, Raleigh, NC
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