Sister chromatid exchanges and chromosomal aberrations in 5-aminouracil-synchronized cells.

5-AU-synchronized cells of Allium cepa L.meristems show increased yields of chromosomal aberrations as well as SCE's. However, although a caffeine post-treatment increases the frequency of 5-AU-induced abnormal ana-telophases, it has a negligible influence on the 5-AU-induced SCE's. These results strongly suggest that the mechanisms through which the 5-AU-induced DNA damage is transformed into chromosomal aberrations and SCE's are at least partly different.