Genetic Recombination Induced by Ultraviolet Light
When bacteria are exposed to ultraviolet (UV) light, the principal photoproducts to be formed in their DNA are pyrimidine dimers. These dimers are of the cyclobutane type and are formed between adjacent pyrimidine bases in the same single strand (Setlow, 1966). It is also known that wild type cells survive exposure to UV light by means of a recovery mechanism in which the pyrimidine dimers are excised from the DNA forming single strand gaps. The twin helix is then reconstructed by DNA synthesis using the intact opposite strand as template. Certain strains that carry mutations in loci designated uvr are unable to excise pyrimidine dimers, and are abnormally sensitive to the lethal effects of UV light (Setlow and Carrier, 1964; Boyce and Howard-Flanders, 1964).
KeywordsVortex Recombination Sedimentation Proline Arginine
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