Adaptive alleles in modern humans

(a) Selective sweeps result in a reduction in polymorphism surrounding the locus of selection. (b) Lactose tolerance has evolved independently in Europeans and Africans and in the Middle East. Each of the SNPs conferring lactase persistence is located in an intron of a gene adjacent to the LCT gene(a) Selective sweeps result in a reduction in polymorphism surrounding the locus of selection. (b) Lactose tolerance has evolved independently in Europeans and Africans and in the Middle East. Each of the SNPs conferring lactase persistence is located in an intron of a gene adjacent to the LCT gene

(a) Allele in Allele in population Haplotype before selection Haplotype after selection population I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ‘ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I Selective sweep (b) Chromosome 2 LCT ’ MCM6\\ 46.3 kb ,,,,,,,,,,,,, ————————— MCM636.2 kb \‘\\\ 5' Z/fiIEIEIEIm-mfl: 3’ _________ ‘\\\ I ‘\\\ —————————————— lntron 13 \‘\\ II Intron 9 \‘xc Ancestral I TAAGTTACCA AAGATAA GTAG TC: GGCICGGTGG Derived I TAAGTTACCA AAGATAA GTAG TG GGCICGGTGG 44009 44010 -13915 —13910 —13907 —22018 bp bp bp bp bp bp | l l | l I Middle East Europeans Europeans 3 different African populations