Seven different scenarios under which QTL parameters (main and epistatic effects), in addition to , to be simulated in ideal F₂ and RI (DH) populations regarding the number of segregating loci in different layers of a hypothetical signaling pathway defined in model (2) containing 9 FGUs,

1‘0’ in the cells indicates the situations where parents are not segregating and have the same functional alleles at all loci within the unit (the unit is functional), whereas ‘x’ indicates the situation where both parents share the same mutant allele(s) at one or more loci within the unit such that the unit is non-functional (the segregating locus or loci in the parents are non-complementary). is the total number of the segregating loci in the populations. 2“Effect” is the maximum pathway phenotypic value on trait X of the corresponding S, T and B loci (or units) specified in model (2) (Fig. 1B). 3FD is functional dependency. There are two types of FD: (I) functional dependency of the downstream FGU loci on loci of their upstream FGUs, and (II) mutual functional dependency of loci from one another in the same FGUs. 4N1 is the total number of genetic parameters simulated in the populations; N2 is the population size of the simulated populations and the expected number of possible multilocus genotypes in each simulated population under Hardy-Weinberg equilibrium.