What does the phosphorylation of Cdc25 by M-Cdk do? Question 4 options: It inactivates Cdc25, which promotes activation of more M-Cdk. It activates Cdc25, allowing the cell to exit mitosis. It activates Cdc25, which inactivates M-Cdk. It inactivates Cdc25, preventing further activation of M-Cdk. It activates Cdc25, which in turn activates more M-Cdk.

It activates Cdc25, which in turn activates more M-Cdk

Explanation:

Cyclin are enzymes that regulate cell cycle progression by the activation of cyclin-dependent kinases (CDKs). These cyclins have no enzymatic activity on their own but they can activate Cdks by binding and phosphorylating them. CDKs can be activated by phosphorylation of activating sites and/or dephosphorylation of inactivation sites. Moreover, M-phase cyclins are cyclins that form M-CDK complexes in order to modulate the cell's entry into mitosis. Cdc25 is a phosphatase involved in the eukaryotic cell cycle which is well-known to regulate the entry into and progression during S (DNA Synthesis) phase and mitosis. In this regard, it has been shown that mitotic phosphorylation of Cdc25 by M-Cdks increases its intrinsic phosphatase activity, thereby Cdc25 is able to remove inhibitory phosphates from M-Cdk and, consequently, activate more M-Cdks.