A physical assay for meiotic recombination in Coprinus cinereus.

We have used the polymerase chain reaction (PCR) method to monitor meiotic recombination in the basidiomycete Coprinus cinereus. We used DNA-mediated transformation to recover strains with modifications of the trp1 locus. The modifications were designed to introduce unique PCR priming sites separated by a homologous 2.4 kb region in which crossing over could occur. We showed that exchange occurred in this region at the frequency expected for a typical region of this genome (2.4 kb should correspond to a genetic length of 0.08 cM). We also detected products resulting from crossing over in DNAs extracted from cells in meiotic prophase. The assay should be useful for monitoring exchange in mutants that cannot complete meiosis.