Absence of ultraviolet-stimulated repair replication in the nuclear and chloroplast genomes of Chlamydomonas reinhardti

Abstract

Repair replication of DNA following ultraviolet irradiation has been examined in the nuclear and chloroplast genomes, respectively, of the green alga Chlamydomonas reinhardti. Ultraviolet doses (at 254 nm) up to 14 200 ergs/mm 2 led to suppression of normal semiconservative DNA replication but no stimulation of repair replication in either nuclear or chloroplast DNA. These findings are consistent with our previous report that pyrimidine dimers are not excised from the DNA in this organism. Chlamydomonas apparently lacks the excision-repair mode of DNA repair that has been well documented in bacteria and some eucaryotic systems.