DNA homology requirements for mitotic gap repair in Drosophila.

We used P transposable-element mobilization to study the repair of double-strand DNA breaks in Drosophila melanogaster premeiotic germ cells. Distribution of conversion tracts was found to be largely unaffected by changes in the length of sequence homology between the broken ends and the template, suggesting that only a short match is required. However, the frequency of repair was highly sensitive to single-base mismatches within the homologous region, ranging from 19% reversion when there were no mismatches to 5% when 15 mismatches were present over a 3455-bp span.