The chromosome-breaking activity of the restriction endonuclease Alu I in CHO cells is independent of the S-phase of the cell cycle.

The restriction endonuclease Alu I induces chromosomal aberrations in living Chinese hamster ovary (CHO) cells. Multiple fixation times reveal that the chromosome-breaking activity of Alu I is similar to that of ionizing radiation in that it is independent of the S-phase of the cell cycle. These results indicate that DNA double-strand breaks are the ultimate lesions for the production of chromosomal aberrations in all stages of the cell cycle.