Abstract
Complex traits have been modeled under various modes of two-locus inheritance. One example of a two-locus threshold model is the situation where an individual is susceptible to a disease trait if he or she carries three or more disease alleles. Under this model, if each locus is examined individually the inheritance appears recessive for some mating types and dominant for others. We developed a heterogeneity test, the Model-heterogeneity test, where an admixture of dominant and recessive sibships can be present. The properties of the Model-heterogeneity test were examined and compared to the Admixture test. The power of the Model-heterogeneity test to detect linkage is comparable to that of the Admixture test.