Mutant Saccharomyces cerevisiae cells lacking the gene encoding securin would arrest in the metaphase stage of the cell cycle. This is because securin normally gets degraded during anaphase, allowing sister chromatids to separate, but in the absence of securin degradation, the cells cannot progress beyond metaphase. The lack of securin degradation leads to the accumulation of separase inhibitor, preventing the activation of separase, which is necessary for sister chromatid separation.