We used PLINK [23] to calculate the probability that one allele is shared IBD (Z1), and we calculated IBS2*_ratio and the percent of informative SNPs as described by Stevens et al. [24]. Briefly, IBS2*_ratio is equal to (IBS2*)/(IBS2*+IBS0), and the percent of informative SNPs is equal to (IBS0+IBS2*)/(IBS0+IBS1+IBS2), where IBS0 is the total number of observations in which two discordant homozygotes are present, and IBS2* results when two concordant heterozygotes are compared between any pair of individuals.
