Path: utzoo!mnetor!uunet!husc6!bloom-beacon!gatech!mcnc!ecsvax!hes
From: hes@ecsvax.UUCP (Henry Schaffer)
Newsgroups: sci.bio
Subject: Re: Rape: a genetic catastrophe
Message-ID: <4577@ecsvax.UUCP>
Date: 7 Feb 88 03:07:52 GMT
References: <517@gtx.com> <5129@cit-vax.Caltech.Edu> <2201@bloom-beacon.MIT.EDU> <4165@sigi.Colorado.EDU>
Organization: NC State Univ.
Lines: 39
Summary: single locus vs. polygenic basis for behavioral traits

In article <4165@sigi.Colorado.EDU>, pell@boulder.Colorado.EDU (Anthony Pelletier) writes:
> ...  [much deleted, including all context]
>   There are good data that
> show causal relationships between genotype and personality traits ...
>  but I don't mean to imply that
> environment has no effect.  As I said in my last posting, the study to which I
> refered was conducted on the Amish in part for that reason).
> We are going to have to face the fact that alot of what we are is heritable.
> At least on form of manic depression has been added to the list of genetic
> diseases (there is another, less well-done study linking another form of
> bipolar disorder to the X chromosome--reference on request).
> ... 
> -tony

  I'n not arguing with anyone - the above quote with no context is just to
show what made me want to post the following *discussion*.

  There are many single locus controlled genetic defects which have 
multiple effects including affecting/altering
personality traits.  The ease of detection and
study of a single locus trait with good penetrance makes it a good
subject for publication.  However this type of genetic control seldom
represents the genetic variation underlying the broad variation seen in
normal individials in a real population.
  Also there is a bias here - the very conditions (e.g., good penetrance,
clearcut major effect, ...) that make for identification and ease of study,
also are exactly those which mean that the environmental effect is
relatively small.  Therefore the effects of the environment tends to
be underplayed when discussing single locus effects.
  The statistical methodology for analysis of polygenic traits (ie.,
quantitative genetics) basically starts out assuming that the trait is
a result of *both* the genetic effects and the environmental effects -
with the relative proportions yet to be determined.  The usual procedure
is to test for the existence of genetic variation (i.e., is heritability
significantly larger than 0?) - and so it can be said that the
quantitative geneticist starts out assuming that the environment *has*
an effect.

--henry schaffer  n c state univ