Selective
sweep of a novel advantageous mutation
The left-hand panel shows patterns of eight SNPs
in six distinct haplotypes among eight (haploid)
individuals: ##1 & 2, and 4 & 5 are identical.
Note that #3 differs from ##1 & 2, and #8 from #7, by
single new SNPs.
A novel SNP
indicated by the red star
arises by a new mutation in a single individual, #6.
The linked SNPs to the left & right are shared
with the haplotype in ##4 & 5, which indicates common
ancestry.
If the novel SNP
confers a major adaptive advantage, strong
positive selection will take it to fixation in a few
generations. Genetically linked SNPs on either
side will also become fixed, even though they are selectively
neutral, with no selective advantage in
themselves. Natural Selection therefore "sweeps" all genetic
variation out of the chromosome region. Such a sweep occurs only in the absence of
genetic recombination, and is therefore expected to
be limited to a relatively small region.
Figures © 2013 by
Sinauer; Text material © 2024 by Steven M. Carr