BULKED SEGREGANT ANALYSIS USING MICROSATELLITES - MAPPING OF THE DOMINANT WHITE LOCUS IN THE CHICKEN

In order to perform a linkage study, the genotypes of a large number o f individuals from a segregating population need to be determined. In case the phenotype to be mapped is influenced by a single locus or a m ajor gene, sampling of the DNA from individual animals with the same p henotype into a single pool (bulked segregant) can reduce the number o f typings. In this study we used bulked segregant analysis in order to map the Dominant White locus in the chicken. In a pilot experiment, w e showed that allele frequencies can be accurately estimated from pool ed samples using fluorescently labeled microsatellite markers. A segre gating population for the Dominant White locus was obtained by perform ing a cross between a white male chicken (Genotype Ii for Dominant Whi te) and a black female chicken (ii). The resulting progeny of 21 white and 18 black chickens were divided in two pools. Genotypes for both t he parents and the pools were determined using 168 fluorescently label ed microsatellite markers, of which 68 were informative. The relative allele frequencies between the pools were estimated for these 68 infor mative markers. One marker (MCW188) was found to segregate with the Do minant White locus. Subsequent typing of all individuals from this cro ss and an additional 148 animals from five different families showed o nly two recombinants between the marker and the Dominant White locus, resulting in a LOD(linkage) score (log(10) of odds) of 36. Using the p ooled DNA approach, the Dominant White locus was successfully mapped o n linkage group 22 of the East Lansing reference family at a distance of 2 cM from MCW188.