[Taxacom] biased gene conversion

[John Grehan]

From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Friday, February 13, 2009 11:00 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] biased gene conversion

> Hi John,
>     I agree that biased gene conversion would allow the spread of a
mutant, > but if that mutation is truly harmful, then natural selection
would still 
>weed it eventually (very quickly on a geological time-scale).

Presumably if the mutant was a recessive the weeding out could only act
on homozygotes, so perhaps it could not weed out the entire population
of alleles?

> If the mutant is simultaneously both harmful (as sickle-cell gene is
when 
> possessed in both copies) or helpful (sickle-cell gene possesed as a
single
>  copy), that is a whole different
> story.         

Or neutral - another story also.

> As for Dover, I wasn't even aware of his book.  

I get the impression not many people are.

> However, after a quick check I see that he has been criticized for
failing
>  to mention Darwin's "correlated variability" (i.e. pleiotropy). 

Not sure that would make any difference

> In any case, Dover has a clear advantage over Darwin in access to
modern 
> knowledge.  But not having read his book myself, I can't comment on
how 
> helpful his fanciful "correspondence" with Darwin might be.  

Dover uses the "correspondence" as a rhetorical device to explain
molecular drive mechanisms.

> As for the subject of natural selection, perhaps he makes a good
argument, 
> or perhaps it is just semantics (i.e., how wide would Darwin's concept
of 
> natural selection now be if he also had access to knowledge of
molecular 
> evolution?).  

Dover does not exclude natural selection, but the assumption that
nothing much happens without natural selection is put into question.

> I'll have to get a copy of Dover's book to read and critique it for
myself,
>  but I just hope he didn't prematurely attach too much importance to
biased
>  gene conversion (the importance of which has not had time to be fully

> explored and debated). 

How much time does one need? Anyway, biased gene conversion is just one
molecular drive mechanism. I'm sure that one could come up with any
number of objections to the potential importance of molecular drive for
evolution. But then, one can come up with any number of objections for
the importance of natural selection in evolution also. The main
difference is that most people don't take that path.

John Grehan
  
        -------Ken Kinman

**********************************************
John Grehan wrote: 
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....
It would seem to in that biased gene conversion would allow the spread
of a mutant without requiring differential reproductive success.... 
Dover wrote a whole book of imaginary correspondence between himself and
Darwin on that very subject. 


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