Eighty-eight S4 animals (22 males and 22 females from each selected line) were genotyped using the MegaMUGA mouse genotyping array (Geneseek, Lincoln, NE, USA). The array provides robust calls for >77 000 single nucleotide polymorphisms (SNPs). For this analysis, genetic distances were calculated for each pair of samples, based on the number of identical alleles at each marker and then summed over all markers. Next, the between-group and within-group distances were calculated following the analysis of molecular variance approach (Excoffier et al. 1992).
