Haseman & Elston (1972) introduced a sib pair method using
classical regression analysis to detect
linkage between a polymorphic marker locus and any quantitative trait locus.
Most of the diseases
mapped to date follow simple Mendelian, single locus transmission. But
there are many familial
diseases that do not follow simple Mendelian segregation, for example
diabetes, several forms of
cancer, etc. In this paper, we extend Haseman and Elston's sib pair
method to two unlinked
quantitative trait loci each linked to one of two unlinked polymorphic
marker loci. For the two-locus
epistatic model, we give a general formulation of the complete
regression model and details of the
regression coefficients in terms of variance components.