Hydroxyurea induces sister chromatid exchanges in G2: Implications for the formation of chromosomal aberrations

Abstract

Lateral roots of Vicia faba were grown for one cell cycle in the presence of 5-bromodeoxyuridine (BrdUrd) and then for another one in the presence of thymidine. Between BrdUrd and thymidine treatments half the number of roots were exposed for 1 h to the antibiotic streptonigrin (SN). Some roots were also exposed to hydroxyurea (HU) during the colchicine treatment the last three hours before fixation. SN was an efficient inducer of both chromosomal aberrations and sister chromatid exchanges (SCE). HU alone produced very few aberrations, but when given as post-treatment to SN, the drug strongly potentiated the induced aberration frequency. Unexpectedly, the HU treatment also increased both the spontaneous and the induced SCE-frequency. The experimental results, which indicate a residual semiconservative DNA synthesis in G2, are discussed in relation to hypotheses for the formation of chromosomal aberrations.