Abstract
The kinetics of in vitro and in vivo thymine dimerization of grass pea ( Lathyrus sativa L.) DNA have been studied. The results showed that the amount of thymine dimers in isolated DNA was two fold higher than in irradiated seedlings. Pyrimidine dimers were excised from the DNA during the incubation of the UV-irradiated seedlings. Excision occurred within the first 6 hr of incubation in the dark. Similar proportions of dimers disappeared during photoreactivation. The decrease in the amount of thymine dimers in DNA was accompanied by their accumulation in the acid-soluble fraction. The enhanced incorporation of labeled thymidine into DNA after UV-irradiation in the presence of hydroxyurea indicates the possibility of unscheduled synthesis in the course of DNA repair after UV-irradiation of seedlings.
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