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From: gagen@bgsuvax.UUCP (kathleen gagen)
Newsgroups: sci.med
Subject: Re: Re: sex and color
Message-ID: <299@bgsuvax.UUCP>
Date: Mon, 10-Nov-86 19:37:06 EST
Article-I.D.: bgsuvax.299
Posted: Mon Nov 10 19:37:06 1986
Date-Received: Tue, 11-Nov-86 06:26:54 EST
References: <2302@bucse.bu-cs.BU.EDU> <7858@tekecs.TEK.COM>
Organization: Bowling Green State University,OH
Lines: 31

> In article <2302@bucse.bu-cs.BU.EDU>, gasp@bu-cs.BU.EDU (Isaac Kohane) writes:
> > 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? :-)
> 
> 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?
> 
> -- 
> 			   Mike Sellers

Yes.  It is correct that the second X chromosome in human females sits
unused in the nucleus and can be cytologically recognized as a "Barr body".
Although only one X chromosome is transcriptionally active (codes for the
production of protein) in each female cell, the transcriptionally active
chromosome may vary from one cell to another within the same individual.


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Kathi Gagen