USE OF GENOMIC EXCLUSION TO ISOLATE HEAT-SENSITIVE MUTANTS IN TETRAHYMENA

[摘要] We have used the abnormal form of conjugation known as "genomic exclusion" to isolate a collection of heat-sensitive mutants of Tetrahymena pyriformis , syngen 1. Growth at room temperature in bacterized medium and no growth at 40°C in the same medium was the criterion used for the isolation. The mutant strains were tested for growth in pure (axenic) culture in proteose peptone medium; of the 31 strains which grew normally at room temperature and not at 40°C in that medium, 21 also failed to grow at 37°C. Preliminary results of complementation tests suggest that most, if not all, the mutations are recessive and that a variety of genes was affected. A detailed genetic analysis was performed on one mutant (H9). The results are all consistent with the idea that the heat-sensitive phenotype of this mutant is determined by a single recessive mutation, designated ts -2. Heterozygotes ts -2/+ yield heat-sensitive segregants during vegetative growth; we interpret this finding as another example of allelic exclusion , a phenomenon universally encountered among heterozygotes in syngen 1 of T. pyriformis . Our results are discussed in the context of some questions of current interest in Tetrahymena genetics.

[学科分类] 医学（综合）