Genetic Model THG ( T rait H eterogeneity with G ene-Gene Interaction). The penetrance tables for Trait I and Trait II are presented. Cell values indicate penetrance level, or the probability of having the trait, given the corresponding multilocus genotype. For Trait I, a Mendelian recessive genetic model is used, in which the trait is penetrant only when two copies of the high risk (B) allele are present. For Trait II, the ''diagonal'' genetic model first described by Frankel & Schork  and later by Li and Reich  is used. Two loci (2 and 3) are involved, each with two alleles (A and B), and the trait is penetrant only when exactly two copies of the high risk allele from either locus are present.