INFERRING THE MAJOR GENOMIC MODE OF DOMINANCE AND OVERDOMINANCE

The mode of within-locus gene action in most genomic regions is termed as the major genomic mode, i.e., it is the within-locus allelic effec ts in most regions of the genome. Determining whether dominance or ove rdominance is the major genomic mode is important for two long-standin g evolutionary genetics issues: 1. How is the genetic variation in mos t genomic regions maintained? 2. What is the major mechanism for heter osis? Many efforts have been made, but almost all of them suffer some explanational difficulties. Here we propose an alternative inference a pproach. It is based on the existent theoretical results on the correl ation of the recombination rate and the level of neutral variation in different genomic regions. Positive and negative correlations suggest dominance and overdominance, respectively, as the major genomic mode. Zero correlations imply either few selected sites or about equal compo sition and distribution of dominant and overdominant regions in the ge nome, depending on the data distribution. This approach not only avoid s all the problems associated with earlier approaches, but it is also particularly useful in organisms where controlled breeding is difficul t. Well-corroborated data in Drosophila and recently emerging data in mice and humans all suggest dominance as the major genomic mode.