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We use Drosophila melanogaster to study mechanisms and regulation of genetic recombination. To Drosophila geneticists, "recombination" is synonymous with crossing over; we use "recombination" in the more general sense, meaning any exchange of DNA information, whether reciprocal (as in crossovers) or unidirectional (as in gene conversion). Recombination occurs in several contexts, including:
Meiotic recombination is crucial for chromosome segregation. Crossovers generate physical links between homologous chromosomes, allowing them to segregate from one another accurately to generate haploid gametes. A beneficial byproduct of meiotic recombination is that it generates increased diversity by allowing the genes inherited from two different parents to be put together into new combinations. Defects in meiotic recombination result in aneuploidy or sterility.
Double-strand break repair. Repair of DNA double-strand breaks (DSBs), which result from exposure to ionizing radiation (X rays, gamma rays, cosmic rays), from problems encountered during DNA replication, or from excision of DNA transposable elements, occurs through either end joining or homology-directed mechanisms. As with other DNA repair pathways, inherited deficiencies in DSB repair can cause predispositions to various cancers.
Interstrand crosslink repair. Several anti-cancer drugs, including cisplatin, nitrogen mustards, psoralen, and mitomycin C, exert their cytotoxic effects by inducing crosslinks between the two strands of the double helix. The mechanisms by which cells normally repair such breaks are poorly understood, but the primary repair pathway is believed to involve recombination.
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