ULTRAVIOLET LIGHT INDUCED LINKING OF DEOXYRIBONUCLEIC ACID STRANDS AND ITS REVERSAL BY PHOTOREACTIVATING ENZYME

Abstract
The irradiation of DNA in solution with UV light with doses approximating those used for inactivation of transforming activity causes (1) the irreversible hydrogen-bond breakage, most likely in internal regions of the DNA molecule and (2) the formation of formamide-and heat-stable linkages between the two complementary DNA strands. Repair of the latter damage is catalyzed by the photoreactivating enzyme from bakers'' yeast The cross-links are in keeping with the observations of others on the irradiation of thymine in the frozen state and may be due to the formation of dimers of thymine.