4 The role of sequence homology in the repair of DNA double-strand breaks in Drosophila

Abstract

This chapter discusses the double-strand break repair in Drosophila melanogaster. The chapter focuses on the effect of sequence homology and chromosome organization on gene conversion in mitotically dividing, premeiotic germline cells of Drosophila. In all systems, double-strand break repair requires significant sequence similarity between the interacting DNA partner molecules. Thus, there is an inverse relationship between the number of nucleotide mismatches and the frequency of gene conversion. Two different types of experiments have been used to examine the extent of homologous sequence that is required to support the P -element-induced gene conversion in Drosophila . These types are: homology requirements for gene conversion of point mutations; and homology requirements for gene conversion of insertions. Another way to examine the length of sequence required for homologous recombination is to examine the length of sequence required at the broken ends of the DNA molecule. The study of P -element transposition and excision products provides an instructive example of the homology required of the broken end to initiate the efficient double-strand break repair.