(a) The DGRP is a collection of inbred strains derived from the wild population in Raleigh, NC. The spectrum of mutations and genetic variation in the DGRP is a reflection of the combined effects of mutations, drift, and selection. In this study, we used the DGRP genotype data (Huang et al., 2014) to estimate the parameter (see Materials and methods), the microarray expression data collected by (Ayroles et al., 2009) and organismal phenotypes (sleep traits from Harbison et al., 2009) to estimate genetic variance among the DGRP lines (). (b) We derived 25 MA lines from the inbred line DGRP_360. These lines were kept with small population sizes of 10 females and 10 males such that there is minimal natural selection. At generation 60, we sequenced the MA lines to estimate mutation rate () and , and obtained microarray gene expression and organismal phenotypic data to estimate mutational variance ().