%0 Journal Article %A Emily B. Josephs %A Young Wha Lee %A John R. Stinchcombe %A Stephen I. Wright %T Association mapping reveals the role of mutation-selection balance in the maintenance of genomic variation for gene expression %D 2015 %R 10.1101/015743 %J bioRxiv %P 015743 %X The evolutionary forces that maintain genetic variation for quantitative traits within populations remain unknown. One hypothesis suggests that variation is maintained by a balance between new mutations and their removal by selection and drift. Theory predicts that this mutation-selection balance will result in an excess of low-frequency variants and a negative correlation between minor allele frequency and selection coefficients. Here, we test these predictions using the genetic loci associated with total expression variation (‘eQTLs’) and allele-specific expression variation (‘aseQTLs’) mapped within a single population of the plant Capsella grandiflora. In addition to finding eQTLs and aseQTLs for a large fraction of genes, we show that alleles at these loci are rarer than expected and exhibit a negative correlation between effect size and frequency. Overall, our results show that mutation-selection balance is the dominant contributor to genomic variation for expression within a single, outcrossing population. %U https://www.biorxiv.org/content/biorxiv/early/2015/02/26/015743.full.pdf