Dan MacArthur has a post up, Climate genes: positive or balancing selection?, where he questions the interpretation of data from a recent paper, Adaptations to Climate in Candidate Genes for Common Metabolic Disorders:
The critical point I want to make is that while positive selection will usually tend to increase the frequency of an allele until it reaches 100% frequency, balancing selection can result in a situation where an allele reaches a stable frequency that is less than 100%. For a case of heterozygote advantage, the stable frequency will be the point at which the selective advantage of heterozygotes is cancelled out by the selective disadvantage of homozygotes.
Read the whole post. I've had some of the same thoughts as Dan before. I guess my main issue is that I am generally cautious about interpreting data as evidence of heterozygote advantage. There are theoretical reasons for this; if you have ...
