Saturday, September 5, 2015

Dominance versus additivity

Posted by Jessica Abbott
X-chromosome-rated comic: The Dominant Gene, by Rather Humerus. From
Sorry for being a bit late in choosing an article for next week's meeting. Don't worry, though, it's very short.

An important enterprise in genetics today is in trying to tie together molecular data with quantitative genetics. This paper uses theory to try to explain why a gene that behaves as dominant on the molecular level can still show up as part of the additive genetic variance for a trait, when investigated with quant gen.

Abstract: Whenever allele frequencies are unequal, nonadditive gene action contributes to additive genetic variance and therefore the resemblance between parents and offspring. The reason for this has not been easy to understand. Here, we present a new single-locus decomposition of additive genetic variance that may give greater intuition about this important result. We show that the contribution of dominant gene action to parent–offspring resemblance only depends on the degree to which the heterozygosity of parents and offspring covary. Thus, dominant gene action only contributes to additive genetic variance when heterozygosity is heritable. Under most circumstances this is the case because individuals with rare alleles are more likely to be heterozygous, and because they pass rare alleles to their offspring they also tend to have heterozygous offspring. When segregating alleles are at equal frequency there are no rare alleles, the heterozygosities of parents and offspring are uncorrelated and dominant gene action does not contribute to additive genetic variance.

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