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 effects in most regions of the genome. Determining whether dominance or overdominance is the major genomic mode is important for two long-standing evolutionary genetics issues: 1. How is the genetic variation in most genomic regions maintained? 2. What is the major mechanism for heterosis? Many efforts have been made, but almost all of them suffer some explanational difficulties. Here we propose an alternative inference approach. It is based on the existent theoretical results on the correlation of the recombination rate and the level of neutral variation in different genomic regions. Positive and negative correlation suggest dominance and overdominance, respectively, as the major genomic mode. Zero correlations imply either few selected sites or about equal composition and distribution of dominant and overdominant regions in the genome, depending on the data distribution. This approach not only avoids all the problems associated with earlier approaches, but it is also particularly useful in organisms where controlled breeding is difficult. Well-corroborated data in Drosophila and recently emerging data in mice and humans all suggest dominance as the major genomic mode.