Question

Which protein is often referred to as the "guardian of the genome" due to its role in cell cycle arrest?

• A. p21
• B. p53
• C. Cyclin D
• D. Rb protein

Hint:

{Quick Memory Trick:}
{p53 = Protects DNA.
Whenever DNA damage occurs, p53 stops the cell cycle and either repairs the DNA or eliminates the damaged cell.

Answer 1

The Correct Option is B

Topic: Cell Cycle Regulation
The cell cycle is controlled by various checkpoints that ensure DNA is intact before division. Tumor suppressor proteins act as regulatory signals to prevent the multiplication of damaged cells.
Steps:
Understanding the Question: We need to identify the specific regulatory protein known as the "guardian of the genome" because of its ability to stop the cell cycle when DNA is damaged.
Key Formulas and Approach: Focus on tumor suppressors. When DNA damage is detected, a specific protein acts as a transcription factor to trigger repair or cell death.
Detailed Solution:
The protein p53 acts as a cellular monitor for DNA damage.
Upon detecting stress or damage, p53 levels rise and it induces the expression of p21, which inhibits CDKs to halt the cell cycle in the G1 phase.
This pause allows time for DNA repair; if repair is impossible, p53 triggers apoptosis (programmed cell death).
Because it preserves the integrity of the genetic material by preventing mutations from being passed on, it is nicknamed the "guardian of the genome."