Statistical genetics of normal variation in family data for oligogenic diseases.

A quadrivariate quantitative genetic analysis detected significant heritabilities for four simulated quantitative traits (Q1-Q4) with additive genetic pleiotropy between traits Q1, Q2, and Q3. Using univariate segregation analysis, we tentatively detected five major loci: one each for Q2, Q3, and Q4 and two, at different maxima, for Q1. Bivariate one-locus segregation analysis identified significant major locus pleiotropy for Q1, Q2, and Q3 only; and suggested identity between one of Q1's major genes and that for Q2, and between the second Q1 major gene and that for Q3. Patterns of linkage, supportive of inferences from the bivariate segregation analyses, were detected between three candidate genes and the major genes for Q1, Q2 and Q4.