Question

Cdc25 - Loss of function mutation: no __________ activation; cell cannot enter ___-phase and continues to grow.

a) G1-Cdk, G1
b) S-Cdk, S
c) M-Cdk, M
d) G2-Cdk, G2

Answer 1

Cdc25 loss of function mutation prevents the activation of G2-Cdk complex, hindering the cell's ability to enter M-phase and promoting continuous growth without division.

Step-by-step explanation:

The question asks what the loss of function mutation in Cdc25 results in with regards to cell cycle progression. The correct answer is d) G2-Cdk, G2. Cdc25 is a phosphatase that activates the cyclin-dependent kinase (Cdk) complexes necessary for the cell cycle to progress from one phase to the next. In particular, Cdc25 activates the G2-Cdk complex, which is required for the transition from G2 phase to M phase. If there is a loss of function mutation in Cdc25, the G2-Cdk complex cannot become active, and thus the cell is unable to enter M-phase, leading to continuous growth without division. This ties in with the broader understanding of the cell cycle and its regulation by tumor suppressor genes such as p53, which, when mutated, can lead to unregulated cell division and potentially to cancer.