Variance-components QTL linkage analysis of selected and non-normal samples: Conditioning on trait values

Standard variance-components quantitative trait loci (QTL) linkage analysis can produce an elevated rate of type 1 errors when applied to selected sam ples and non-normal data. Here we describe an adjustment of the log-likelih ood function based on conditioning on trait values. This leads to a likelih ood ratio test that is valid in selected samples and non-normal data, and e qual in power to alternative methods for analyzing selected samples that re quire knowledge of the ascertainment procedure or the trait values of non-s elected individuals. Genet. Epidemiol. 19(Suppl 1):S22-S28, 2000. (C) 2000 Wiley-Liss, Inc.