Evolution__3rd_Edition

8 Two-locus
and Multilocus
Population Genetics
W e begin with an example of a character that is
controlled by a multilocus genotype. The set of genes
that an individual inherits from one of its parents form a
“haplotype,” and the theory of population genetics for
multilocus systems traces haplotype frequencies through
generations. The chapter has two main purposes. One is to
introduce population genetic theory for multilocus systems,
and the distinctive concepts that apply to it but not to
one-locus models: we look at the multiple-locus concepts
of linkage disequilibrium, together with its causes, of
recombination, and of multiple-peaked fitness surfaces.
The other purpose is to see the conditions under which
single-locus models of evolution are inadequate, and
multilocus models are necessary: the main condition is the
existence of linkage disequilibrium. We also look at how
multilocus genomic sequences can be used to test whether
selection has recently been acting in a region of the DNA.
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