Chromosoma

, Volume 45, Issue 4, pp 401–429

The development of the macronucleus in the ciliated protozoan Stylonychia mytilus

  • Dieter Ammermann
  • Günther Steinbrück
  • Ludwig von Berger
  • Wolf gang Hennig
Article

DOI: 10.1007/BF00283386

Cite this article as:
Ammermann, D., Steinbrück, G., von Berger, L. et al. Chromosoma (1974) 45: 401. doi:10.1007/BF00283386

Abstract

Ciliated protozoa are characterized by generative micronuclei and vegetative polyploid macronuclei. Micronuclei of Stylonychia mytilus contain 1 600 times as much DNA per haploid genome as E. coli. Most of this DNA is shown to be repetitive. The development of the macronucleus involves, as demonstrated by cytology, only 1/3 of the chromosomes which in a first replication phase are polytenized in probably 5 replication steps and appear as giant chromosomes. At this developmental stage considerable amounts of repetitive DNA are still present in the chromosomes. During the subsequent disintegration phase more than 90% of the DNA are eliminated from the macronucleus anlage. The remainder is further replicated five times and composes the final macronucleus. Since this DNA reassociates with a reaction rate almost identical to an ideal second order reaction its kinetic complexity can be determined by comparison with the kinetic complexity of E. coli DNA. Macronuclear DNA reassociates with a kinetic complexity of 26 times the kinetic complexity of E. coli DNA (corrected for GC content) which indicates that macronuclear DNA sequences exist at a ploidy level of 4 096 C. We assume that macronuclear DNA may be present only once per haploid genome. In this case it represents only 1.6% of the DNA in micronuclei or 10% of the DNA in the giant chromosome stage.

Copyright information

© Springer-Verlag 1974

Authors and Affiliations

  • Dieter Ammermann
    • 1
    • 2
    • 3
  • Günther Steinbrück
    • 1
    • 2
    • 3
  • Ludwig von Berger
    • 1
    • 2
    • 3
    • 4
  • Wolf gang Hennig
    • 1
    • 2
    • 3
  1. 1.Zoologisches Institut der Universität TübingenGermany
  2. 2.Max-Planck-Institut für BiologieTübingenGermany
  3. 3.Institut für Molekularbiologie II der Universität ZürichSwitzerland
  4. 4.Zentrum für Innere Medizin und Kinderheilkunde Universität UlmUlmFederal Republic of Germany

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