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Smallness of the human Y chromosome

Rich Cooper richcooper1 at mindspring.com
Wed Nov 1 16:47:43 EST 2000


It seems to me that this hypothesis could be mathematized rather easily
into a few differential equations, and plotted, to see if the system is
stable at Y% male and X% female.

-Rich Cooper


Laurence Martin Cook <LCOOK at fs1.scg.man.ac.uk> wrote in message
news:8tplkg$j4i$1 at mercury.hgmp.mrc.ac.uk...
> In mosquitoes (Aedes) there are M-linked (= Y-linked) meiotic drive
> genes and suppressor genes on the m (or X) chromosome.  Numerous
> evolutionary events seem to have taken place, so that inter-
> population crosses produce sex ratio distortion while intra-
> population crosses do not, or do so to a much lesser extent.  The Mm
> chromosomes are equally large and carry many other loci.
>
> Laurence
>
>
>
> > Andrew Gyles  <syzygium at alphalink.com.au> wrote:
> >
> > >Under natural selection a human population in which the males had
> > >the 'anti-X gamete' Y chromosome would suffer the disadvantages of a
> > >surplus of males and a scarcity of females. In the long run natural
> > >selection would favour subsequent mutants of the 'anti-X gamete' Y
> > >chromosome in which those mutant genes that discriminated against the
> > >production of X-bearing gametes in spermatogenesis or sperm maturation
> > >were deleted or rendered inactive.
> >
> > This is the step in the argument that I doubt.  A Y chromosome
> > with meiotic drive *always* has a local advantage over one without,
> > even when the population as a whole is suffering badly from
> > excessive males.  Group selection might possibly be able to
> > push down the frequency of driven Y, but even if one accepts that
> > group selection is a realistic possibility here, it tends to be
> > weak and slow compared to individual selection.
> >
> > On the other hand, the X and the autosomes see a straightforward
> > advantage in not allowing the Y they're with to push them into
> > a male zygote when males are wildly overrepresented, so X and
> > autosomal suppressors are straightfowardly advantageous.  It
> > seems to me, therefore, that the usual way a driven Y stops being
> > driven is that a non-Y suppressor becomes fixed, not that the
> > drive locus is damaged or deleted.
> >
> > There are a fair number of observations of meiotic drive in the
> > literature; you could look for references to suppressors/revertants
> > and see what chromosome they're on.  I'd predict they're usually
> > not on the Y.
> >
> > Mary Kuhner mkkuhner at genetics.washington.edu
> >
> >
> > ---
> >
> >
> >
> > Laurence M. Cook
> The Manchester Museum
> University of Manchester
> Manchester M13 9PL U.K.
> and:_lcook2 at excite.com
>
>
> ---
>
>









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