Lower-than-expected linkage disequilibrium

Dan Garrigan garrigan at asu.edu
Wed Sep 5 15:29:59 EST 2001


On 3 Sep 2001, Andrew Gyles wrote:

> An article in Am J Hum Genet 2001 Sep; 69(3): 582-589 reports
> lower-than-expected linkage disequilibrium between tightly linked markers in
> humans.
> 
> Would not gene conversion on a large scale also reduce the sequence
> variation in the human population? As I understand the mechanism, when a
> gene is converted an allele is eliminated, so:
> 
>    "widespread gene conversion = widespread allele loss".

If intra-genic conversion occurs in an individual that is heterozygous within
the conversion tract, you can think of it more as a form of mutation, whereby 
a new haplotype is created during that round of meiosis.  The donor haplotype
can still be reproduced intact, so its not exactly like you're thinking
about.  There may be some slight effect that you allude to, but certainly it
would be nothing compared to the effects of genetic drift and crossing-over.  

Dan

P.S. What did you think of the idea presented in that paper?  Gene conversion
can definitely create the heterogenous pattern of L.D. that those authors
found, but...how widespread and frequent is it? What else could cause that
pattern of L.D. or is it just random noise?

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