Role of mitotic replication genes in chromosome duplication during meiosis

In the yeast Saccharomyces cerevisiae, DNA synthesis preceding meiosis requires the expression of replication genes used during mitosis. Diploids carrying either a temperature-sensitive lesion in cdc4 (a gene required for initiation of mitotic DNA synthesis) or a lesion in cdc8 (a gene controlling mitotic polymerization) completed premeiotic DNA synthesis at a permissive but not at a restrictive temperature. The roles of cdc4 and cdc8 were evaluated by characterizing the kinetics of premeiotic DNA synthesis after a shift to a restrictive temperature. In the cdc8 diploid, DNA synthesis was immediately inhibited, consistent with a role in polymerization. In contrast, cdc4 exhibited residual DNA synthesis characteristic of an initiation function. The cdc4 gene function was completed much earlier in the meiotic cycle than the cdc8-mediated step.