Figure 2.—

Crossing over is reduced in dmc1, mei5, and sae3 mutants. (A) Diploids containing one circular and one linear copy of chromosome III were introduced into sporulation medium and samples were harvested at the time points indicated. Genomic DNA was subjected to pulsed-field gel electrophoresis followed by Southern blot analysis, hybridizing with a probe containing the THR4 gene on chromosome III (Chua and Roeder 1998; Agarwal and Roeder 2000). The positions of linear monomers, dimers, and trimers and of molecules that have sustained one or more DSBs are indicated to the right of the gel. (B) Quantitative analysis of physical recombinants. To calculate the percentage of DNA in crossover products (percentage of recombinants), the sum of signals for dimer and trimer molecules was divided by the sum of signals for monomers, dimers, and trimers (plus DSBs if applicable) for each lane. Strains analyzed are wild type (WT, TBR737), dmc1 (TBR1028), sae3 (TBR1063), mei5 (TBR1089), dmc1 sae3 (TBR1797), and dmc1 mei5 (TBR1798).