Meiotic recombination in Drosophila Msh6 mutants yields discontinuous gene conversion tracts.
Crossovers (COs) generated through meiotic recombination are important for the correct segregation of homologous chromosomes during meiosis. Several models describing the molecular mechanism of meiotic recombination have been proposed. These models differ in the arrangement of heteroduplex DNA (hDNA) in recombination intermediates. Heterologies in hDNA are usually repaired prior to the recovery of recombination products, thereby obscuring information about the arrangement of hDNA. To examine hDNA in meiotic recombination in Drosophila melanogaster, we sought to block hDNA repair by conducting recombination assays in a mutant defective in mismatch repair (MMR). We generated mutations in the MMR gene Msh6 and analyzed recombination between highly polymorphic homologous chromosomes. We found that hDNA often goes unrepaired during meiotic recombination in an Msh6 mutant, leading to high levels of postmeiotic segregation; however, hDNA and gene conversion tracts are frequently discontinuous, with multiple transitions between gene conversion, restoration, and unrepaired hDNA. We suggest that these discontinuities reflect the activity of a short-patch repair system that operates when canonical MMR is defective.
Radford
Sarah J
SJ
Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Sabourin
Mathilde M
MM
McMahan
Susan
S
Sekelsky
Jeff
J
D000483:Alleles; D000818:Animals; D001482:Base Composition / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics; D003434:Crossing Over, Genetic; D004251:DNA Transposable Elements / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D005785:Gene Conversion / Q000235:genetics*; D008540:Meiosis; D008957:Models, Genetic; D009692:Nucleic Acid Heteroduplexes / Q000235:genetics; D016366:Open Reading Frames / Q000235:genetics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics*
D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C094443:G-T mismatch-binding protein; D009692:Nucleic Acid Heteroduplexes