Excision-repair patch size in DNA from human KB cells treated with UV-light, or methyl methanesulfonate

We have used the method of combined bromodeoxyuridine density label and radioactive label to measure the size of the repair patches appearing in the DNA of KB cells following treatment with UV-light or MMS. The repair patch size distribution was found to be the same for both agents, corresponding to the insertion of 34-40 nucleotides. These results, confirm recent results obtained by the bromodeoxyuridine-photolysis technique, that simple alkylating agents induce 'long patch' repair in human cells.