The preceding models emphasize allelic associations and corresponding interactions one SNP at a time. Researchers have recently adapted existing quantitative genetic modeling techniques to include genetic similarity among unrelated individuals (Lee et al. 2011a; Yang et al. 2010, 2011b). These methods have been organized into the GCTA suite of genome-wide association tools and are available to researchers online (http://www.complextraitgenomics.com/). Rather than estimating the cumulative influence of all known causal loci (which are, in principle, unknown), these models estimate a relationship matrix for all unrelated persons. They characterize the genetic relationships between the jth and kth individual across all genetic markers i = 1 to i = n, with minor allele frequency p as (3)Ajk=1n∑i=1n(xij−2pi)(xik−2pi)2pi(1−pi).
