tokens: In an effort to dissect some of these complexities , we performed linkage analysis of gene expression transcripts of members of Centre d ' Etude du Polymorphisme Humain ( CEPH ) Utah families to determine the heritability of transcripts and the evidence for regulatory quantitative trait loci ( QTLs ) and we performed pairwise bivariate linkage analysis and principal - component analysis ( PCA ) for data - reduction to evaluate the evidence for shared genetic effects .