Parasexual Recombination in Dictyostelium discoideum: Selection of Stable Diploid Heterozygotes and Stable Haploid Segregants

Haploid strains of Dictyostelium discoideum bearing temperature-sensitive mutations have been used to select stable diploid, heterozygotic clones, which arise at low frequency (about 10(-5)). Segregants arise from such diploids at low frequency (about 10(-3)). The diploids were heterozygous for resistance to cycloheximide and were phenotypically sensitive to the drug. Growth of the diploid cells in the presence of cycloheximide automatically selected those segregants bearing the resistant allele, and facilitated examination of the assortment of unselected markers. The combination of the two selective methods provides a workable system of genetic analysis in this species. We have used this method to locate six markers on three different linkage groups.