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From: gasp@bu-cs.BU.EDU (Isaac Kohane)
Newsgroups: sci.med
Subject: Re: sex and color
Message-ID: <2375@bu-cs.bu-cs.BU.EDU>
Date: Sun, 9-Nov-86 20:50:45 EST
Article-I.D.: bu-cs.2375
Posted: Sun Nov  9 20:50:45 1986
Date-Received: Mon, 10-Nov-86 02:36:27 EST
Organization: Boston U. Comp. Sci.
Lines: 23

Isaac Kohane:
   >> Well, it seems that women can in fact see more than men.
   >> [...]
   >> Now, as we all know, women have twice as much X chromosome as men do.
   >> Therefore, if there are multiple alleles (versions of that gene at
   >> that locus) for the red pigment (as is suggested by recent experiments
   >> in this area), then a women could have one allele on one X chromosome,
   >> and another allele on the second X chromosome. Each allele would have
   >> a different peak absorption wavelength. It might be then, that some
   >> women are in fact quadrichromatic. What do they see that we don't? :-)

    Mike Sellers:
>   If I remember correctly, the second X chromosome in females sits unused in
>   the nucleus (it never "unbundles" in interphase like the rest of the 
>   chromosomes do).  These are called "Barr bodies", after the guy who 
>   discovered them.  If my recollection is correct, then this would seem to 
>   imply that females do not benefit from anything on the "extra" X chromosome>   Can anyone closer to a genetics text confirm or deny my remembrance?

Close, but no cigar :-). The inactivation of the X chromosomes is a random
process, such that in a given tissue, there are two populations of
cells, each one having a different X chromosome activated. Therefore,
both alleles would be expressed.

			Isaac