[Taxacom] biased gene conversion

John Grehan jgrehan at sciencebuff.org
Fri Feb 13 20:06:38 CST 2009


From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Wednesday, February 11, 2009 3:36 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] biased gene conversion

Dear All,
       I find it a little hard to swallow that "many of the genetic changes 
> leading to human-specific characters may be the result of the fixation of 
> harmful mutations," 

Hard to swallow does not mean that it is not true. The part I don't understand is why many of the genetic changes have to represent harmful mutations.

> and that this contrasts with "the traditional Darwinistic view that they 
> are the result of natural selection in favour of adaptive mutations." 

It would seem to in that biased gene conversion would allow the spread of a mutant without requiring differential reproductive success.

> Although biased gene conversion could accelerate some evolutionary change 
> (pushing more grist through the mill), natural selection (the mill itself) 
> is still going to eventually act on that change. 

Only if there is a change in fitness.

> Framing this as an either/or question just seems too simplistic.

I would agree in the sense that both processes may be involved in a co-evolutionary interaction (suggested by Gabriel Dover years ago).

> Natural selection keeps on "selecting" no matter how the genetic variation 
> arises or what environmental changes occur. Frankly, I don't think Darwin 
> would have any problem with biased gene conversion.

Dover wrote a whole book of imaginary correspondence between himself and Darwin on that very subject.

> However, I think he might take issue with the premature speculation on what
>  biased gene conversion might be correlated with (such as homeothermy).  
> And there are obviously forces which counteract biased gene conversion (and
>  I believe that I read that many primate genomes have actually become less
>  GC-rich compared to some other mammal groups).

No doubt, but until the process is explored rather than dismissed it will remain mysterious.

John Grehan


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