Power analysis for a simulated QTL. The power to detect a QTL at a 5% significance level with Haley-Knott (HK) regression and FIA for the four simulated cases presented in Table 1, ranging from total fixation (Case 1) to equal allele frequencies in both lines (Case 4). Thick solid line – FIA with additive and dominance effects; thick dashed line – FIA with additive effects only; thin solid line – HK-regression with additive and dominance effects; thin dashed line – HK-regression with additive effects only. For each case, 6000 replicates were simulated and the pedigree in each replicate had four founders and 800 F2 individuals. In Figure 1a, an additive QTL effect (a) of 2 and a QTL dominance effect (d) of 0 was simulated together with a residual variance of 98. In Figure 1b, a = 1 and d = 1, and in Figure 1c, a = 0 and d = 2.