Abstract: | Summary A temperature-sensitive non-agglutinative mutant of Saccharomyces cerevisiae was isolated and characterized. The mutation, sag2, affected sexual agglutination, conjugation and production of -mating pheromone at a restrictive temperature, but not the response to -mating pheromone. Genetic analyses showed that the mutation was recessive and in the MAT locus. The sag2 mutation complemented with mat 2 but not with mat 1 These results suggest that sag2 is in the MAT 1 gene and that at a restrictive temperature the mutation, sag2, inactivated the MAT 1 product, a positive regulator of -mating functions. The sag2 mutation is like mat 1-5 in its retention of response to -mating pheromone. However, at 25 °C, sag2 cells were competent to mate, whereas mat 1-5 cells were not. Hence, sag2 is regarded as a new allele in the MAT 1 gene, which we designate mat 1-11. |