Analysis of resynthesis tracts in repaired Escherichia coli deoxyribonucleic acid.

Excision repair of ultraviolet radiation-induced damage in a wild-type strain of Escherichia coli has been examined, using two methods for characterizing the resynthesis step of the repair process. Comparison of data obtained after both isopycnic analysis of repaired deoxyribonucleic acid and sedimentation velocity analysis of deoxyribonucleic acid after selective photolysis of bromouracil-containing repaired regions has shown that the repaired deoxyribonucleic acid molecules contain a semicontinuous distribution of sizes of repair tracts. Further analysis of our data suggests two major classes of repair patches, one abut 20 to 40 nucleotides in length, and the other containing 1,600 to 2,000 nucleotides. Under the conditions employed, approximately 2 to 10% of the fully repaired regions are long repair patches.