Does heterogeneity in opsin genes demand selection pressure

Paul-Michael Agapow p.agapow at ic.ac.uk
Mon May 14 01:44:46 EST 2001

C.J.L. Wolf <C.J.L.Wolf at ncl.ac.uk> wrote:
> Just a quick question re: the evolution of opsin genes.
> [snip]
> continuation of established heterogeneity in the population. But I'm sure
> I remember vaguely some maths in a pop-science book that said that a
> million years from now we'd all end up with the same surname, as the
> statistics of surname inheritance tend to select names out at random. As
> an embryo is more likely to carry an X chromosome from its mother than its
> father, presumably similar stats should apply?

I think (not knowing what book it was you were reading) the author might
be referring to Gamblers Ruin. To simplify, in a group of gamblers
(competing species / genes / alleles etc.) of equal skill (fitness), the
numbers will drop of time just through random fluctuation. You go
bankrupt (extinct), you're no longer in the game. So over time, the
number of surnames would eventually reduce to one.

But this only applies if no new names are created and there are no
forces acting to maintain diversity.

> My question is whether, as is often stated, we must invoke positive
> selection pressure for the female monkeys that have enhanced colour vision
> in order to account for the maintainance of several opsin isoforms in the
> population. If the hardy-weinberg equilibrium applies to genes on the

If I understand the situation correctly, this seems like a reasonable
hypothesis. For further references perhaps check out "Evolutionary
Genetics" (is that the right title? the blue cover book) by John Maynard
Smith as a reasoably acessible treatment.

Paul-Michael Agapow (p.agapow at ic.ac.uk), Biology, Imperial College
"Pikachu's special power is that he's monophyletic with lagomorphs ..."


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