Interval mapping of human QTL using Sib pair data

Abstract

A modified Wald test is proposed for the testing of QTL effect, and its asymptotic distribution is provided and hence the thresholds of the test can be well determined. Then a genome search strategy is proposed. Methods for calculating the test statistic and simulating the thresholds capable of controlling the overall type I error probability are provided. We also propose an alternative multi-point interval mapping method, which estimates the IBD proportions at the flanking makers with the joint distribution of the numbers of alleles IBD at multiple markers. The likelihood ratio test is always among the most powerful methods. However, the asymptotic distribution of the LR test statistic for interval mapping is not yet studied. We apply the result of Self and Liang (1987) to the interval mapping problem and deduce that the asymptotic distribution of the LR test statistic is a mixture of Chi-square(1) and Chi-square(2).