GENETIC-MAPPING OF MUTATIONS USING PHENOTYPIC POOLS AND MAPPED RAPD MARKERS

Genetic markers facilitate the study of inheritance and the cloning of genes by genetic approaches. Molecular markers detect differences in DNA sequence, and are thus less ambiguous than phenotypic markers, whi ch require gene expression. We have demonstrated a molecular approach to the mapping of mutant genes using RAPD markers and pooling of indiv iduals based on phenotype. To map genes by phenotypic pooling a strain carrying a mutation is crossed to a strain that is homozygous for the wild-type allele of the corresponding gene. A set of primers correspo nding to mapped RAPDs distributed throughout the genome and in couplin g phase with respect to the wild type parent is then used to amplify D NA from wild type and mutant pools of F2 individuals. Linkage between the mutant gene and the RAPD markers is visualized by the absence of t he corresponding RAPD DNA bands in the mutant pool. We developed a mat hematical model for calculating the probability of linkage between RAP Ds and target genes and we succesfully tested this approach with the m odel plant Arabidopsis thaliana.