The Mitotic Chromosomes of the Cellular Slime Mould Dictyostelium discoideum: A Karyotype Based on Giemsa Banding

SUMMARY: All seven mitotic chromosomes of the haploid cellular slime mould Dictyostelium discoideum have been identified and numbered using Giemsa banding techniques. Although size differences are not marked, the size distribution is one long, three medium length, and three shorter chromosomes. Each chromosome has a distinctive banding pattern. All seven chromosomes appear to have terminal or near terminal centromeres. Apparent connexions between chromosomes explain the controversy concerning chromosome number (five or seven) in D. discoideum. The mitotic index of exponential-phase axenic cultures of D. discoideum is 2%. By returning aggregating amoebae to growth medium the mitotic index could be reproducibly raised to approximately 6%.