Meiosis in a temperature-sensitive DNA-synthesis mutant and in an apomictic yeast strain (Saccharomyces cerevisiae).
It is shown that in the temperature-sensitive yeast mutant (Saccharomyces cerevisiae) spo 11 at the restrictive temperature of 34 degrees C. (1) premeiotic DNA synthesis is nearly completely blocked; (2) the nucleus enters meiotic prophase indicated by the formation of axial cores and polysynaptonemal complexes; (3) the kinetic apparatus functions normally at meiosis I and II; (4) early spore formation occurs in nearly all cells but it is variable and all spores eventually degenerate. It is concluded that chromosome replication is not a prerequisite for the functions listed above. The apomictic yeast strain 4117 produces 2 diploid spores. It is shown that a diploid which produces 2-spored asci, synthesized from 4117, no. 5, and an adenine requiring strain (1) has a normal meiotic prophase with abundant synaptonemal complexes; (2) has only one meiotic spindle; (3) has spores which form red clones more frequently than normal or u.v.-treated vegetative cells form ade/ade red sectors through mitotic recombination. It is concluded that this apomictic yeast has maintained meiotic prophase, but that one of the two meiotic divisions is suppressed.
D002875:Chromosomes / Q000502:physiology / Q000648:ultrastructure; D004261:DNA Replication; D008540:Meiosis; D008854:Microscopy, Electron; D009154:Mutation; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000502:physiology; D013172:Spores, Fungal; D013696:Temperature