General effect of a selective sweep for an advantageous DNA variant.
General effect of a selective sweep for an advantageous DNA variant.
(A) Heterozygosity profile before selection. Imagine that an advantageous DNA variant has just occurred on a founder chromosome 22. We might expect significant heterozygosity, as shown by the six representative chromosome 22s.
(B) Heterozygosity profile after positive selection over many generations. Vertical transmission of the founder chromosome 22, recombination, and continued positive selection for the advantageous variant will result in an increased frequency of the advantageous DNA variant plus closely linked DNA variants, causing reduced heterozygosity for that chromosome segment.
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