Article: Evolution: Looking for an advantage
- From: "Robert Karl Stonjek" <rstonjek@xxxxxxxxxxxxxx>
- Date: Mon, 19 Jun 2006 12:01:22 -0400 (EDT)
Nature Reviews Genetics 7, 496 (July 2006) | doi:10.1038/nrg1900
Evolution: Looking for an advantage
Patrick Goymer
Skewed patterns of polymorphism around a locus can imply that it has
recently been subject to selection. Many studies have therefore looked for
evidence of selection in the large sets of polymorphism data that have
recently become available. Teshima et al. have now shown that the
reliability of empirical approaches to assessing such data depends on
demography and the nature and history of the allele being selected.
Polymorphism at neutral sites in the genome is not entirely free from the
influence of selection. A neutral allele at a locus that happens to be close
to an advantageous allele at a locus under selection will 'hitchhike' to
near-fixation along with the selected allele. Therefore, levels of
polymorphism at neutral sites will be reduced if selection has acted nearby.
There are several models of expected neutral polymorphism against which data
can be compared when looking for selection. However, the results are often
sensitive to the assumptions of the model. Therefore, a simple empirical
approach is often used for genome-wide analyses, in which sites with the
most skewed polymorphism patterns are assumed to be those that are linked to
selected sites. But what are false-discovery and false-negative rates in
this approach, and are there systematic biases against discovering certain
types of selected site?
Teshima et al. simulated data sets for the evolution of modern humans and
the domestication of maize. They attempted to make their data realistic by
including bottlenecks (to mimic non-sub-Saharan human populations) or
constant population sizes (for sub-Saharan populations), and strong
selection on previously neutral alleles (for the relatively sudden
artificial selection imposed by man in domesticating maize) compared with
weaker selection on new mutations (for wild plant populations).
Source: Nature Genetics
http://www.nature.com/nrg/journal/v7/n7/full/nrg1900.html
Posted by
Robert Karl Stonjek
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