The evolution of the genetic architecture of traits under artificial selection
Yvonne C. J. Wientjes, Piter Bijma, M.P.L. Calus, Bas J. Zwaan, Joost van den Heuvel · Socio-Environmental Systems Modeling · 2019
In the presence of non-additive effects, the average effect of a causal locus depends on the allele frequency at the locus itself and at the loci with which it interacts. Drift and selection change the allele frequencies, thereby changing the genetic architecture of traits, i.e. the average effects at the loci underlying the trait and the contribution of these loci to the genetic variance. In agriculture, this process has likely been accelerated by the recent introduction of genomic selection, which is more accurate and focuses more on genes with large effects compared to traditional selection. Traditional selection has proven to maintain genetic variation for many generations, but it is unknown whether genomic selection maintains variation. We aim to identify and quantify the mechanisms determining the change in genetic architecture and genetic variation under genomic and traditional selection. We simulated a population for 50 discrete generations with selection. Each generation contained 40 sires and 400 dams with 6 offspring. The simulated genome contained 10 chromosomes of 1 Morgan each and 2000 causal loci. We simulated different levels of additive, dominance and epistatic effects. The simulated epistatic interaction network was based on results in yeast, with many loci with few interactions and few loci with many interactions, and only pairwise-interactions with normally distributed effects. Results will provide insights into the change in genetic architecture and genetic variation in populations under selection, and how this depends on the mode of gene action, the number of causal loci and the intensity of selection.