Mechanism of chromosome exchange formation in human fibroblasts: Insights from [open quotes]chromosome painting[close quotes]

Journal Article · Fri Jan 01 04:00:00 EST 1993 · Environmental and Molecular Mutagenesis; (United States)

DOI:https://doi.org/10.1002/em.2850220407· OSTI ID:7075468

Brown, J M; Evans, J W; Kovacs, M S ^[1]

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1. Stanford Univ., CA (United States)

The authors have used the techniques of premature chromosome condensation (PCC) and fluorescence in situ hybridization (FISH) with a library for human chromosome 4 to analyze the rate of rejoining of chromosome breaks and development of exchange aberrations in AG1522 human fibroblasts. AG1522 cells were irradiated in plateau phase with 10 Gy and fused with mitotic HeLa cells either immediately after irradiation or at intervals up to eight days later. The slides were then hybridized with the chromosome 4 library and unrejoined breaks and exchange events (visualized as bicolor chromosomes) scored in these cells. At the earliest time point after irradiation, the number of exchange events in the irradiated cells was low, but increased with kinetics similar to that of the joining of the breaks. Furthermore, when those cells which had exchange events for their distribution were analyzed , almost all of the cells initially contained one exchange event (1 bicolor chromosome). As time progressed, the number of cells containing exchanges with two exchange events per cell increased as the number with one exchange event per cell decreased. Extrapolation of the number of exchange events to zero time (with an estimate of 20 min for the fusion and condensation times) gave a value consistent with zero exchanges at zero time after irradiation. In a separate experiment, the authors also scored AG1522 cells at the first metaphase after a dose of 6 Gy and were able to show that as many as 50% of the complete exchanges were non-reciprocal in nature, that is, the two broken ends of a single break in chromosome 4 joined to two different chromosomes. These data support the classical breakage-and-reunion model rather than the Revell Exchange Theory of exchange formation. 20 refs., 5 figs.

• OSTI ID: 7075468
• Journal Information: Environmental and Molecular Mutagenesis; (United States), Journal Name: Environmental and Molecular Mutagenesis; (United States) Vol. 22:4; ISSN 0893-6692; ISSN EMMUEG
• Country of Publication: United States
• Language: English

Related Subjects

550400 -- Genetics
560120* -- Radiation Effects on Biochemicals
Cells
& Tissue Culture
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHROMOSOMAL ABERRATIONS
CHROMOSOMES
DNA REPAIR
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
IONIZING RADIATIONS
MUTATIONS
PHYSICAL RADIATION EFFECTS
PRODUCTION
RADIATION EFFECTS
RADIATIONS
REPAIR
STRAND BREAKS
TIME DEPENDENCE