where l was the population mean; X was an incidence matrix for the fixed factors of family, litter and sex; b was a vector of the fixed factors; a and d were the estimated additive and dominance effects respectively; for the ith F2 individual and a putative QTL at a given location; yi was the trait value, cai and cdi were the coefficients for the additive and dominance components respectively, and ei was the residual error.