Xref: utzoo sci.research:641 talk.politics.misc:21636 sci.bio:1824
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!husc6!cs.utexas.edu!ut-emx!ethan
From: ethan@ut-emx.UUCP (Ethan Tecumseh Vishniac)
Newsgroups: sci.research,talk.politics.misc,sci.bio
Subject: Re: Gene Pool
Summary: Tay-Sachs and other "bad" genes
Message-ID: <10276@ut-emx.UUCP>
Date: 7 Feb 89 21:08:04 GMT
References: <674@intvax.UUCP> <1252@meccsd.MECC.MN.ORG> <1254@meccsd.MECC.MN.ORG> <5579@ncsugn.ncsu.edu>
Distribution: na
Organization: The University of Texas at Austin, Austin, Texas
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In article <5579@ncsugn.ncsu.edu>, emigh@ncsugn.ncsu.edu (Ted H. Emigh) writes:
> 
> How can I pass up an invitation (unless Dan is talking about some other
> Ted)?  Let's consider the standard "genetic disease."  Some trait which
> is currently deleterious (to some extent) and currently has a fairly
> low incidence in the population.  Examples are: Tay-Sachs (frequency of
> <10^-3 => or an incidence of <10^-6);  ....{other examples omitted}.
> 
> If the genetic trait is completely neutral, then it would be spread
> through the generation through mutation alone.  However, it would take
> an unbelievably long time.  A trait that has a mutation rate of 10^-5
> would take about 10,000 GENERATIONS to increase in frequency from current
> frequencies to about 10% (which would lead to an incidence of people with
> the trait of about 1%).  Note the 10,000 generations is about 200,000 years,
> which is older than Homo sapiens.
> 

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'm not afraid of dying     Ethan Vishniac, Dept of Astronomy, Univ. of Texas
 I just don't want to be     {charm,ut-sally,ut-emx,noao}!utastro!ethan
 there when it happens.      (arpanet) ethan@astro.AS.UTEXAS.EDU
    - Woody Allen            (bitnet) ethan%astro.as.utexas.edu@CUNYVM.CUNY.EDU

These must be my opinions.  Who else would bother?