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Genetics. 1988 Sep;120(1):135-43. doi: 10.1093/genetics/120.1.135.

Genomic exclusion and other micronuclear anomalies are common in genetically defective clones of tetrahymena thermophila.

Genetics

R A Pitts, F P Doerder

Affiliations

  1. Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 2A9.

PMID: 17246475 PMCID: PMC1203485 DOI: 10.1093/genetics/120.1.135

Abstract

Genomic exclusion (GE) is an abnormal form of conjugation which has previously been described in detail for three hypodiploid strains of Tetrahymena thermophila. These strains cannot form gametic nuclei and by failing to participate in normal reciprocal fertilization their genes are excluded from exconjugants. To determine whether GE is a general property of infertile strains, we surveyed genetically and cytogenetically 19 additional strains of T. thermophila to determine why they failed to contribute genes to sexual progeny. Crosses to genetically marked tester strains showed that seventeen of these strains undergo GE. In each case GE appears to be due to the failure of the defective partner to form functional gametic nuclei. The normal conjugant, however, contributes to its defective partner a haploid nucleus identical to its own, and following diploidization of the unfertilized nuclei, the conjugants separate retaining the old macronuclei. Cytofluorimetric measurement of micronuclear DNA content in 18 strains suggests that aneuploidy is the proximate cause of GE; eleven strains were hypodiploid, five were diploid and three were hyperdiploid. Many irregular cytogenetic events were observed in conjugants presumably not undergoing GE, including, in some instances, abnormal meiosis in the normal partner. Since genomic exclusion was found in both wildtype and mutant clones, the results suggest that it should be possible by appropriate crosses to identify genomic exclusion strains of any genotype.

References

  1. Genetics. 1987 Sep;117(1):13-23 - PubMed
  2. Genetics. 1963 May;48:737-44 - PubMed
  3. Proc Natl Acad Sci U S A. 1976 Sep;73(9):3243-7 - PubMed
  4. J Protozool. 1971 Aug;18(3):515-7 - PubMed
  5. J Protozool. 1971 Aug;18(3):509-15 - PubMed
  6. Mech Ageing Dev. 1975 May-Aug;4(3-4):263-79 - PubMed
  7. Genetics. 1976 Jul;83(3 PT.2):489-506 - PubMed
  8. J Cell Sci. 1975 May;17(3):471-93 - PubMed
  9. J Exp Zool. 1975 May;192(2):237-58 - PubMed
  10. Genetics. 1967 Apr;55(4):797-822 - PubMed
  11. Genetics. 1967 Apr;55(4):823-37 - PubMed
  12. Genetics. 1983 Jun;104(2):257-70 - PubMed
  13. Genetics. 1973 May;74(1):107-14 - PubMed
  14. J Protozool. 1964 Nov;11:465-73 - PubMed
  15. J Protozool. 1963 Nov;10:413-20 - PubMed
  16. Mech Ageing Dev. 1979 Nov;11(4):253-68 - PubMed

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