Extrachromosomal inheritance in Schizosaccharomyces pombe

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Abstract
Spontaneous chloramphenicol (cap r)- and erythromycin (ery r)-resistant mutants were isolated from strain ade7–50 h - and the antimycin-resistant mutant ana r-8 ade 7–50 h- of Schizosaccharomyces pombe (Sch. p.). By mitotic segregation analysis all 154 cap r- and 120 ery r-mutants derived from ade 7–50 h - proved to be recessive chromosomal, whereas all 108 cap r- and 200 ery r-mutants originating from ana r-8 were extrachromosomally inherited. The rate of spontaneous cap r- and ery r-mutants was about hundredfold in ana r-8 compared to ade 7–50 h -. Growth of cap r-and ery r-mutants was not inhibited by chloramphenicol or erythromycin, respectively, in glucose-medium and only slightly in glycerol-medium at concentrations which completely inhibited ana r-8. By mitotic segregation-, tetrad-, and mitotic haploidization-analysis the extrachromosomal inheritance of mutants derived from ana r-8 was established. Segregational patterns of cap r- and ery r-determinats during mitosis, meiosis, and mitotic haplidization of diploids are discussed.