Abstract
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.
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Selected References
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- ALLEN S. L., MISCH M. S., MORRISON B. M. GENETIC CONTROL OF AN ACID PHOSPHATASE IN TETRAHYMENA: FORMATION OF A HYBRID ENZYME. Genetics. 1963 Dec;48:1635–1658. doi: 10.1093/genetics/48.12.1635. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Allen S. L. Cytogenetics of genomic exclusion in Tetrahymena. Genetics. 1967 Apr;55(4):797–822. doi: 10.1093/genetics/55.4.797. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Allen S., Gibson I. Genome amplification and gene expression in the ciliate macronucleus. Biochem Genet. 1972 Jun;6(4):293–313. doi: 10.1007/BF00486122. [DOI] [PubMed] [Google Scholar]
- Grass F. S. Genetics of the ST serotype system in Tetrahymena pyriformis, syngen 1. Genetics. 1972 Apr;70(4):521–536. doi: 10.1093/genetics/70.4.521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nanney D L, Dubert J M. The Genetics of the H Serotype System in Variety 1 of Tetrahymena Pyriformis. Genetics. 1960 Oct;45(10):1335–1349. doi: 10.1093/genetics/45.10.1335. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nilsson J. R. Suggestive structural evidence for macronuclear "subnuclei" in Tetrahymena pyriformis GL. J Protozool. 1970 Nov;17(4):539–548. doi: 10.1111/j.1550-7408.1970.tb04724.x. [DOI] [PubMed] [Google Scholar]
- Phillips R. B. Inheritance of T serotypes in Tetrahymena. Genetics. 1967 Aug;56(4):667–681. doi: 10.1093/genetics/56.4.667. [DOI] [PMC free article] [PubMed] [Google Scholar]