You isolate a new cdc mutant in budding yeast and call it cdc104. You arrest cdc104 at its restrictive temperature of 37 °C for 2 hours (the length of a cell-cycle in yeast is normally about 90 minutes). You then release the phenotypic arrest by shifting the cdc104 mutant arrested yeast to the permissive temperature of 20 °C, but you release in the presence of hydroxyurea. Hydroxyurea arrests cells in S-phase because it blocks DNA replication. The cells refuse to divide. Now you reverse the order of the treatment, you arrest cells for 2 hours in S phase by adding hydroxyurea. Then you wash out the hydroxyurea but grow the cells at 37°C. Now the cells undergo one round of division before arresting.
- In what phase of the cell cycle does the cdc104 mutant arrest?
- What mammalian cyclin functions at the same point?