title: Sister chromatid fusion initiates amplification of the dihydrofolate reductase gene in Chinese hamster cells.
abstract: We have utilized a dihydrofolate reductase (DHFR) probe in combination with selected probes from other positions along the 2q chromosome arm in a two-color fluorescence in situ hybridization analysis of early DHFR gene amplification events in CHO cells. These studies show clearly that the most frequent initiating event is the formation of a giant inverted duplication, resulting from chromosome breakage and terminal fusion or a reverse unequal sister chromatid exchange. The dicentric chromosomes thus formed initiate bridge/breakage/fusion cycles that appear to mediate subsequent amplification steps to higher copy number.
authors.affiliation: Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: C
authors.initials: C
authors.lastname: Ma
authors.forename: S
authors.initials: S
authors.lastname: Martin
authors.forename: B
authors.initials: B
authors.lastname: Trask
authors.forename: J L
authors.initials: JL
authors.lastname: Hamlin
mesh_terms: D000818:Animals; D016466:CHO Cells; D002869:Chromosome Aberrations; D007446:Chromosome Inversion; D006224:Cricetinae; D003412:Cricetulus; D005784:Gene Amplification / Q000235:genetics*; D015698:Genomic Library; D017404:In Situ Hybridization, Fluorescence; D012854:Sister Chromatid Exchange; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
chemical_list: D013762:Tetrahydrofolate Dehydrogenase