Eliminating Both Canonical and Short-Patch Mismatch Repair in Drosophila melanogaster Suggests a New Meiotic Recombination Model
At the top is a chromatid with a DSB, which enters into recombination with a chromatid on the homologous chromosome. A single-end invasion intermediate may be transient (indicated by brackets) or may give rise to some NCOs. Second-end capture and synthesis produces the two-end engagement intermediate. COs arise by nicking of this intermediate across from the existing nicks (arrowheads). NCOs arise by disassembly of the two-ended engagement intermediate by a helicase. In the version drawn here, resection is symmetric with respect to the DSB and synthesis tracts are the same length as resection tracts, resulting in nicked HJs. It is possible that resection and/or strand invasion/strand capture are asymmetric. It is also possible that synthesis does not extend all the way across the resected region, leaving a three-stranded junction instead of a nicked HJ. These possibilities, while compatible with the data, do not change the major features of the model.