PHENOTYPIC ASSORTATIVE MATING IN SEGREGATION ANALYSIS

A model of phenotypic assortative mating was developed for application in segregation analysis. The model assumed a constant spouse correlat ion across the range of a quantitative trait or the liability to a dis crete trait. Four traits were analyzed to evaluate: 1) the feasibility of applying likelihood analysis to pedigree data in order to distingu ish between assortative mating and shared environmental effects as the source of spouse correlation; and 2) the impact on segregation analys is of the failure to account for either assortative mating or shared e nvironmental effects, as appropriate. Height ratio (the ratio of sitti ng to standing height) and eye color comprised the traits for which th e observed spouse correlation reflected assortative mating; serum chol esterol and peptic ulcers (with genotypes defined by the ABO blood gro up) comprised the traits for which the observed spouse correlation ref lected shared environmental effects. For all four traits the test stat istics agreed with the known cause of spouse correlation; however, sig nificance was not attained for height ratio or serum cholesterol. The ability to distinguish between the causes of spouse correlation in ped igree data presumably depends on trait and sample characteristics whic h remain to be delineated. Despite significant spouse correlation, its omission from the segregation analysis model did not undermine the in ference of major locus inheritance for any of the four traits, However , the lack of an impact for these traits does not preclude an impact f or other traits of ignoring the appropriate spouse correlation in segr egation analysis. (C) 1995 Wiley-Liss, Inc.