A cytogenetic investigation of DNA replication after hydroxyurea treatment: Implications for gene amplification

Although the mechanisms leading to gene amplification are poorly understood, it has recently been proposed that the initial event of amplification is the rereplication of a variable, but relatively large, amount of the genome within a single cell cycle. The authors sought evidence for rereplication of DNA as a basis for gene amplification through two cytogenetic techniques: differential staining for sister-chromatid exchange analysis and premature chromosome condensation. The results observed are consistent with the hypothesis that drug-induced aberrations and the subsequent abnormal segregation of chromosomal fragments are the first steps in the process that leads to gene amplification in drug-treated-mammalian cells.