The mutagenic activity of hydroxyurea in Chlamydomonas reinhardi

Hydroxyurea, an inhibitor of ribonucleotide reductase, increases the frequency of streptomycin resistant mutants in liquid cultures of Chlamydomonas reinhardi after 45 h incubation. After more prolonged incubation in hydroxyurea medium the frequency of streptomycin resistant mutants declines. This may be due to the slower growth rate of streptomycin resistant mutants compared to wild type cells in hydroxyurea containing medium. Studies on solid medium show that both the rate of forward mutation to streptomycin resistance and reverse mutation to nicotinamide independence are increased several fold by growth on hydroxyurea.