The Mercurial Germline Genome of Hypotrichous Ciliates

  • David M. Prescott
  • Michelle L. DuBois
Part of the Stadler Genetics Symposia Series book series (SGSS)


A hypotrichous ciliate contains both a germline nucleus and a somatic nucleus. The germline nucleus, called the micronucleus, contains chromosomes with very high molecular weight DNA. It divides mitotically and undergoes meiosis at cell mating. Its genes are transcriptionally silent during vegetative growth. The somatic nucleus, called the macronucleus, contains only gene-sized DNA molecules ranging in size from ~400 bp to ~15,000 bp with an average of 2200 bp in Oxytricha species. Each different sized molecule is present in the macronucleus in ~1000 copies. There are 24,000 different sized molecules, or a total of 24 × 106 molecules per macronucleus (Lauth et al., 1976). A gene-sized molecule contains a single transcription unit. The ~66 gene-sized, macronuclear molecules characterized for hypotrichs so far consist of a 5 ′ DNA leader, a transcription unit or open reading frame (ORF) for protein-encoding molecules, and a 3′ DNA trailer (Hoffman et al., 1995. All the molecules possess terminal repeats of 3′ dG4T4 with a 14-base or 16-base 3′ tail of the repeat sequence.


Polytene Chromosome Ciliated Protozoan Somatic Nucleus Repeat Pair Nova Gene 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bierbaum, P., Donhoff, T., and Klein, A., 1991, Macronuclear and micronuclear configurations of a gene encoding the protein synthesis elongation factor EF1a in Stylonychia lemnae, Mol. Microbiol. 5: 1567.PubMedCrossRefGoogle Scholar
  2. DuBois, M., and Prescott, D.M., 1995, Scrambling of the actin I gene in two Oxytricha species, Proc. Nad. Acad. Sci. USA 92: 3888.CrossRefGoogle Scholar
  3. Gray, J.T., Celander, D.W., Price, C.M., and Cech, T.R., 1991, Cloning and expression of genes for the Oxytricha telomere-binding protein: specific subunit interactions in the telomeric complex, Cell 67: 807.PubMedCrossRefGoogle Scholar
  4. Greslin, A.F., Loukin, S.H., Oka, Y., and Prescott, D.M., 1988, An analysis of the macronuclear actin genes of Oxytricha, DNA 7: 529.Google Scholar
  5. Greslin, A.F., Prescott, D.M., Oka, Y., Loukin, S.H., and Chappell, J.C., 1989, Reordering of nine exons is necessary to form a functional actin gene in Oxytricha nova, Proc. Natl. Acad. Sci. USA 86: 6264.CrossRefGoogle Scholar
  6. Herrick, G., Cartinhour, S.W., Williams, K.R., and Kotter, K.P., 1987, Multiple sequence versions of the Oxytricha fallax 81-MAC alternate processing family, J. Protozool. 34: 429.PubMedGoogle Scholar
  7. Hicke, B.J., Celander, D.W., MacDonald, G.H., Price, C.M., and Cech, T.R., 1990, Two versions of the gene encoding the 41-kilodalton subunit of the telomere binding protein of Oxytricha nova, Proc. Nad. Acad. Sci. USA 87: 1481.CrossRefGoogle Scholar
  8. Hoffman, D.C., Anderson, R.C., DuBois, M.L., and Prescott, D.M., 1995, Macronuclear gene-sized molecules of hypotrichs, Nucleic Acids Res. 23: 1279.PubMedCrossRefGoogle Scholar
  9. Klobutcher, LA., Jahn, C.L., and Prescott, D.M., 1984, Internal sequences are eliminated from genes during macronuclear development in the ciliated protozoan Oxytricha nova, Cell 36: 1045.PubMedCrossRefGoogle Scholar
  10. Lauth, M.R, Spear, B.B., Heumann, J., and Prescott, D.M., 1976, DNA of ciliated protozoa: DNA sequence diminution during macronuclear development of Oxytricha, Cell 7: 67.PubMedCrossRefGoogle Scholar
  11. Mansour, S.J., Hoffman, D.C., and Prescott, D.M., 1994, A gene-sized DNA molecule encoding the catalytic subunit of DNA polymerase alpha in the macronucleus of Oxytricha nova, Gene 144: 155.PubMedCrossRefGoogle Scholar
  12. Mitcham, J.L, Lynn, A.J., and Prescott, D.M., 1992, Analysis of a scrambled gene: the gene encoding alpha-telomere binding protein in Oxytricha nova, Genes Dev. 6: 788.PubMedCrossRefGoogle Scholar
  13. Mitcham, J.L, Prescott, D.M., and Miller, M.K., 1994, The micronuclear gene encoding b-telomere binding protein in Oxytricha nova. J. Euk.. Microbiol, 41: 478.CrossRefGoogle Scholar
  14. Ribas-Aparicio, R.M., Sparkowski, J.J., Proulx, A.E., Mitchell, J.D., and Klobutcher, L.A., 1987, Nucleic acid splicing events occur frequently during macronuclear development in the protozoan Oxytricha nova and involve the elimination of unique DNA, Genes Dev. 1: 323.PubMedCrossRefGoogle Scholar
  15. Williams, K.R., and Herrick, G., 1991, Expression of the gene encoded by a family of macronuclear chromosomes generated by alternative DNA processing in Oxytricha fallax, Nucleic Acids Res. 19: 4717.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • David M. Prescott
    • 1
  • Michelle L. DuBois
    • 1
  1. 1.Department of Molecular, Cellular and Developmental BiologyUniversity of ColoradoBoulderUSA

Personalised recommendations