Question

Which of the following is correct?

• A. p53 is a tumor suppressor gene and pRB is an oncogene
• B. pRB is an oncogene
• C. p53 and pRB both are tumor suppressor genes
• D. p53 and pRB both are oncogenes

Hint:

p53 = DNA damage checkpoint, pRB = cell cycle gatekeeper.

Answer 1

The Correct Option is C

Step 1: Understanding cancer genetics.
Cancer arises due to uncontrolled cell division, which is regulated by two types of genes: oncogenes (promote division) and tumor suppressor genes (inhibit division).

Step 2: Role of tumor suppressor genes.
Tumor suppressor genes act as cellular checkpoints. They repair DNA damage, regulate cell cycle, and prevent abnormal proliferation of cells.

Step 3: Function of p53 gene.
p53 is known as the “guardian of the genome.” It detects DNA damage and either halts the cell cycle or triggers apoptosis if damage is irreparable.

Step 4: Function of pRB gene.
Retinoblastoma protein (pRB) regulates the G1 to S phase transition in the cell cycle. It prevents uncontrolled cell division by inhibiting cell cycle progression.

Step 5: Evaluating oncogene concept.
Oncogenes promote cell division, but both p53 and pRB do the opposite; they suppress tumor formation. Hence, they are not oncogenes.

Step 6: Disease association.
Mutation or loss of function in p53 or pRB leads to cancer development, confirming their tumor suppressor role.

Step 7: Final conclusion.
Thus, both p53 and pRB are tumor suppressor genes.