Chromosoma

, Volume 88, Issue 2, pp 91–97

Chromonema and chromomere

Structural units of mitotic and interphase chromosomes
  • O. V. Zatsepina
  • V. Yu. Polyakov
  • Yu. S. Chentsov
Article

Abstract

A study of ultrathin sections of normal Chinese hamster cells and cells treated with decreasing concentrations of bivalent cations (Ca2+ and Mg2+) in situ revealed several discrete levels of compaction of DNA-nucleoprotein (DNP) fibrils in mitotic chromosomes and the chromatin of interphase nuclei. At concentrations ranging from 3 mM CaCl2 and 1 mM MgCl2 to ten times less, the chromosomes are found to contain fibrous elements (chromonemata) about 100 nm in diameter. As Ca2+ concentration is gradually decreased to 0.2–0.1 mM, the chromosomes decondense into a number of discrete chromatin structures, the chromomeres. As decondensation proceeds, these chromomeres acquire a rosettelike structure with DNP fibrils radiating from an electron-dense core. Upon complete decondensation of chromosomes, individual chromomeres persist only in the centromeric regions. The following levels of DNP compaction in mitotic chromosomes are suggested: a 10-nm nucleosomal fibril, a 25-nm nucleomeric fibril, and the chromonema, a fibrous structure, about 100 nm in diameter, composed of chromomeres. Interphase nuclei also contain structures which are morphologically similar to the chromomeres of mitotic chromosomes.

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Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • O. V. Zatsepina
    • 1
  • V. Yu. Polyakov
    • 1
  • Yu. S. Chentsov
    • 1
  1. 1.A.N. Belozersky Laboratory of Molecular Biology and Bio-organic ChemistryMoscow State UniversityMoscowUSSR

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