Transmission of radiation-induced acentric chromosomal fragments to micronuclei in normal human fibroblasts

M. N. Cornforth, E. H. Goodwin

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


A simplifying assumption made when calculating the probability of a chromosomal aberration resulting in a micronucleus is that virtually all radiation-induced micronuclei result from acentric fragments. In the present study we used antibodies to chromosomal centromeres (kinetochores) to determine the frequency of centric versus acentric micronuclei in normal human fibroblasts exposed to 6 Gy of 60Co γ rays while they were in density-inhibited growth. Up to 14% of the micronuclei induced by this exposure contained one or more kinetochores; i.e., they were not composed of acentric chromatin. By deleting kinetochore-positive micronuclei from the analysis, and by reconstructing micronucleus frequencies based on the fraction of cells that had divided following radiation exposure, a direct comparison between micronuclei and acentric chromosome fragments was made. On that basis, the probability of an acentric fragment becoming a visible micronucleus in either daughter cell of a dividing pair was estimated to be about 0.6. The distribution of acentric fragments among mitotic cells conformed to Poisson expectation, while the distribution of micronuclei among daughter cells was significantly overdispersed. The phenomenon of overdispersion is discussed in connection with proposed cellular processes that effect a nonrandom segregation of acentric fragments.

Original languageEnglish (US)
Pages (from-to)210-217
Number of pages8
JournalRadiation research
Issue number2
StatePublished - 1991
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Radiation
  • Radiology Nuclear Medicine and imaging


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