enzyme (Tyr 15 of phorylated, the en- -ylation state of any lows replication. The role of Cdk inhibitors in mammalian cells is discussed on page 581. Mitosis rphase (G,) Interphase (G,) Thr161- P Tyr15- P Thr161- P CAK Weel Cdc25 cdc2 kinase cdc2 kinase cdc2 kinase G, fission yeast cell Post-mitotic fission yeast cells Cyclin Cyclin Cyclin Inactive Inactive Active Cyclin Degradation Wild type sion yeast cell cycle phorylation of critical nicrograph of wild interacts with a G2 weel- G2 of phosphorylation of a Veel (step 1). A sepa- another residue (Thr W
The figure below details a pathway in yeast involving kinases and a phosphatase and the regulation of a specific cyclin-cdk complex. CAK kinase controls the phosphorylation of Thr161. The phosphorylation of Tyr15 is controlled by Wee1 and Cdc25. In this problem, focus on the phosphorylation of Tyr15 by Wee1 and Cdc25.
1. If Wee1 kinase was inactive, what would happen to the cyclin-cdc2 complex?
Would the cells enter mitosis and divide more or less often?
Would the cells end up being smaller or larger than normal?
2. If Cdc25 phosphatase was inactive, what would happen to the cyclin-cdc2 complex?
Would the cells enter mitosis and divide more or less often?
Would the cells end up being smaller or larger than normal?

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The cell cycle is highly regulated by different regulatory proteins that includes the cdc2 and cyclin protein. These two are very much important for progression through different cell cycle checkpoints. If anyone of this protein remained elective then the sale will be arrested at that particular checkpoint.
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