USE OF SIB-PAIR LINKAGE METHODS FOR THE ESTIMATION OF THE GENETIC VARIANCE AT A QUANTITATIVE TRAIT LOCUS

Until recently, the sib-pair linkage method of Haseman and Elston coul d only be used for the detection of linkage between a quantitative tra it locus (QTL) and a marker locus. It was not possible to estimate the amount of genetic variance contributed by the QTL or its recombinatio n fraction with the marker locus. With the advent of dense marker maps for nearly every domestic species, every QTL should be located betwee n 2 flanking markers. In this situation, the Haseman-Elston test can b e modified to estimate the variance of a putative QTL as well as its r ecombination fractions with the 2 flanking markers. In the present pap er, we derive 2 different estimation methods for the QTL variance base d on the squared performance of full sibs: in one only the QTL varianc e is estimated, while in the other both the QTL variance and the recom bination fractions are estimated. The method that estimates only the Q TL variance turns out to be more powerful than the other. With respect to the estimation of QTL variance both methods give results close to the true values. However, the estimation of recombination fractions re sulted in an overall underestimation of the true parameters.