, Volume 88, Issue 2, pp 91–97 | Cite as

Chromonema and chromomere

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


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.


MgCl2 CaCl2 Fibril Developmental Biology Chromatin Structure 
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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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