Graphical representation of the genetic model used in the simulation. D1-D4 are disease-causing loci. D5 and D6 influence disease expression if the disease genotype is present. P1-P3 are different phenotypes caused by the disease loci to which they are connected by the lines. The "a" and "b" after the phenotype designation indicate identical phenotypes but caused by different genotypes. D5 changes phenotype P2a into P1 when allele 1 is present. D6 changes the penetrance of P2b when allele 1 is present.