title: Parasexual genetic analysis of the cellular slime mold Dictyostelium discoideum A3.
abstract: Haploid strain A3 of the cellular slime mold Dictyostelium discoideum is valuable for biochemical studies because it is capable of axenic growth. Mutants of A3 temperature-sensitive for growth and resistant to the drugs cycloheximide, acriflavin, or methanol were isolated.--Heterozygous diploid recombinants, formed at low frequency by cell and nuclear fusion, were isolated by selecting temperature-resistant progeny of mixed cultures of two nonallelic temperature-sensitive haploids (LOOMIS 1969). Each drug-resistant mutation was found to be recessive. Two independently isolated methanol-resistant mutants were in one complementation group.--Diploids of A3 heterozygous for drug resistance formed drug-resistant segregants with a frequency of approximately 10(-4). Segregants selected for resistance to a single drug were either haploid or diploid; the fraction which was haploid varied from 0.11 to 0.86, depending on the selected marker. Segregants selected for resistance to two or three drugs were almost all haploid.--Using this parasexual cycle of diploid formation and haploidization, linkage of these temperature-sensitive and drug-resistance mutations to each other and to mutations studied by KATZ and SUSSMAN (1972) and by WILLIAMS, KESSIN and Newell (1974b) was analyzed. The methanol-resistant mutants were found to be partially resistant to acriflavin, and unlinked to the mutant selected for acriflavin resistance, which was methanol-sensitive. Of the expected seven linkage groups in D. discoideum, five, and a possible sixth, have been marked.--Linkage analysis of a mutant abnormal in morphogenesis showed that its phenotype results from two unlinked chromosomal mutations.
mesh_terms: D000167:Acriflavine / Q000494:pharmacology; D004023:Dictyostelium / Q000187:drug effects; D004351:Drug Resistance; D008040:Genetic Linkage; D005838:Genotype; D006238:Haploidy; D000432:Methanol / Q000494:pharmacology; D009154:Mutation; D009235:Myxomycetes; D010641:Phenotype; D011995:Recombination, Genetic; D012723:Sex
chemical_list: D000167:Acriflavine; D000432:Methanol