Figure 1.—

(A) Genetic and physical map of markers along the left arm of chromosome VII. In diploid MG100 (set II), the diploid did not contain the URA3 marker. Diploid YFS0407 (set I) contains both the URA3 marker and a BLE marker (not shown) that subdivides the cyh2-crl3 interval but was not used in the subsequent genetic analysis. (B) Expected vs. observed numbers of crossovers along the left arm of chromosome VII. The expected numbers of exchanges for the tetrads in set I were calculated from a Poisson distribution for each possible tetrad type, based on the average number of crossovers per tetrad (open bars), as described in materials and methods. The observed distribution is shown with solid bars. Also shown is the predicted distribution assuming the two-pathway model in which m = 3 and 8% of crossovers are noninterfering (shaded bars).