Which, if any, of the following observations are consistent with the effect of purifying selection, and which, if any, are consistent with the effect of positive selection?
a) Human populations that are accustomed to high-starch diets have comparatively higher copy numbers of the α-amylase gene.
b) Telomere DNA sequences in vertebrates have tandem TTAGGG repeats
c) Humans show very high levels of heterozygosity at the classical HLA loci.
d) Human populations that live in more northerly latitudes have a high frequency of pale skin color.
e) Human calmodulin and an ortholog in Drosophila each have 149 amino acid differences and differ at just four amino acid positions.

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The Answer of Which, if any, of the following observations are consistent with the effect of purifying selection, and which, if any, are consistent with the effect of positive selection?
a) Human populations that are accustomed to high-starch diets have comparatively higher copy numbers of the α-amylase gene.
b) Telomere DNA sequences in vertebrates have tandem TTAGGG repeats
c) Humans show very high levels of heterozygosity at the classical HLA loci.
d) Human populations that live in more northerly latitudes have a high frequency of pale skin color.
e) Human calmodulin and an ortholog in Drosophila each have 149 amino acid differences and differ at just four amino acid positions.

Which, If Any, of the Following Observations Are Consistent with the Effect