Question

P53 tumor suppressor G1 checkpoint (Step 3):

a) Activation of cyclin
b) Cell enters S-phase
c) Cdc25 - Loss of function mutation: no Cyclin-CDK activation; cell cannot enter S-phase and continues to grow.
d) Check for proper chromosome alignment

Answer 1

The p53 protein is vital for DNA damage control at the G1 checkpoint in the cell cycle. Mutations in p53 can lead to unregulated cell division and cancer development by failing to produce p21 and allowing cells with damaged DNA to continue dividing.

Step-by-step explanation:

The p53 tumor suppressor is crucial at the G1 checkpoint of the cell cycle, ensuring DNA integrity before a cell proceeds to DNA replication in the S-phase. When p53 is mutated and loses its function, it may fail to trigger the production of p21, a cyclin-dependent kinase (Cdk) inhibitor. Without p21, there is no effective block on Cdk activation, leading to unchecked cellular progression to the S-phase and potential tumor growth due to the inheritance of the mutated p53 and further accumulation of mutations in the daughter cells. Moreover, p53, when functioning correctly, can initiate the repair of damaged DNA or trigger apoptosis, thus preventing the propagation of damaged genetic material.

Cancer can result from the breakdown of these regulatory mechanisms, with mutations in genes like p53 leading to a loss of control over the cell cycle, an increase in genetic mutations, and the evolution of cancerous cells.