The human caspase-12 gene is polymorphic for the presence or absence of a stop codon, which results in the occurrence of both active (ancestral) and inactive (derived) forms of the gene in the population. The researchers investigated whether the inactive form has spread because of neutral drift or positive selection (Xue et al., American Journal of Human Genetics, 78:659-670, 2006). They suggest that the inactive form of the gene arose in Africa 100–500 thousand years ago (KYA) and was initially neutral or almost neutral but that positive selection beginning 60–100 KYA drove it to near fixation.
The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, United Kingdom.
Abstract available online.
(C) 2006 by The American Society of Human Genetics.
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