Re: [asa] FYI: Arrogance, dogma and why science - not faith - is the new enemy of

From: Rich Blinne <rich.blinne@gmail.com>
Date: Wed Aug 22 2007 - 08:41:44 EDT

On Aug 21, 2007, at 10:34 PM, PvM wrote:

> So what's the story so far.
>
> Now we get to linkage disequilibrium and the Hill-Robertson effect
> which is important in clonal interference in sexual species, causing
> the actual mutation rate to be much lower than the natural one. All in
> all, there are various reasons why Behe's numbers are suspect and he
> does not help his case by not presenting his own calculations leading
> to the 1 in 10^20, a guestimate which is marked as uncertain and
> speculative by the original source.
>

Let's slow down here for the non-geneticists. First some definitions
of Hill Robertson effect (1966!) and linkage disequilibrium from
Wikipedia:

> Hill and Robertson (1966) described an evolutionary advantage to
> genetic recombination.
> In a finite population subject to natural selection and genetic
> recombination, genetic drift will create random instances of
> linkage disequilibrium. Some will be selectively advantageous,
> others will not. However, the creation of these slows down the
> progress of selection. Recombination breaks down the disequilibria,
> allowing selection to act independently on various loci.
>
> References
> Hill, W. G., and A. Robertson, 1966 The effect of linkage on limits
> to artificial selection. Genet. Res. 8: 269294.

> Linkage disequilibrium is a term used in the study of population
> genetics for the non-random association of alleles at two or more
> loci, not necessarily on the same chromosome. It is not the same as
> linkage, which describes the association of two or more loci on a
> chromosome with limited recombination between them. Linkage
> disequilibrium describes a situation in which some combinations of
> alleles or genetic markers occur more or less frequently in a
> population than would be expected from a random formation of
> haplotypes from alleles based on their frequencies. Non-random
> associations between polymorphisms at different loci are measured
> by the degree of linkage disequilibrium (LD). A comparison of
> different measures is provided by[1]
> Linkage disequilibrium is generally caused by genetic linkage and
> the rate of recombination; mutation rate; random drift or non-
> random mating; and population structure. For example, some
> organisms may show linkage disequilibrium (such as bacteria)
> because they reproduce asexually and there is no recombination
> (r=0) to break down the linkage disequilibrium: D'=(1-r)D.
> It may be instructive to study genetic equilibrium, and its
> application in the Hardy-Weinberg principle.
> The International HapMap Project enables the study of LD in human
> populations online. The Ensembl project integrates HapMap data and
> such from dbSNP in general with other genetic information.
> [emphasis mine]

Is there evidence that Hill Robertson effect is operating in
Chloroquine resistance in Plasmodium? Short answer yes. Long answer
can be found here:

http://scholar.google.com/scholar?q=hill+robertson+effect+Chloroquine
+plasmodium

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Received on Wed Aug 22 08:42:25 2007

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