Figure 1.

prp31-E1 is defective in meiotic S phase. (A) pat1-114, pat1-114 prp31-E1 and pat1-114 cdc5-120 strains were arrested in G₁ and released to meiosis as described in Materials and Methods. Samples were harvested every 2 h for flow cytometry. Positions of 1C (unreplicated) and 2C (replicated) DNA content are indicated. A, asynchronous. (B) Nuclear morphology of cells in (A) after 8 h. Cells were stained with DAPI to visualize nuclei. Cells with two nuclei have completed the first meiotic division and cells with more than three nuclei have completed both meiotic divisions. Bar, 10 µm. (C) The percentage of cells in (B) that completed the second meiotic (MII) division after 8 h was determined by counting cells with more than three nuclei. (D) Percentage of diploid cells completing sporulation was determined by counting asci under phase contrast microscopy, following release of diploid strains to meiosis as described in Materials and Methods.