Section 3: Genetics, Cellular and Molecular Biology
DNA replication, transcription, translation
Subtopic: Fundamentals of DNA replication, transcription, translation
Question Statement:
Which of the following statements are CORRECT?
[P] Viruses can play a role in causing human cancer
IQI A tumor suppressor gene can be turned off without any change in its DNA
sequence
[R] Alteration in miRNA expression levels contributes to the development of
cancer
Options:
(A) P and Q only
(B) Q and R only
(C) P and R only
(D) P, Q and R
4 ---
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2020 Q.13)**
**1. Governing Concept**:
- **Topic**: Cancer Biology & Oncogenesis Mechanisms
- Evaluating cancer biology statements:
- **[P] Viral oncogenesis**: Oncogenic viruses (e.g., HPV, EBV, Hepatitis B/C, HTLV-1) directly cause $\sim 15-20\%$ of human cancers $\rightarrow$ **CORRECT**.
- **[Q] Epigenetic silencing of tumor suppressors**: Tumor suppressor genes (e.g., *CDKN2A/p16*, *BRCA1*, *MLH1*) can be completely silenced without DNA sequence mutation via promoter hypermethylation and repressive histone modifications $\rightarrow$ **CORRECT**.
- **[R] MicroRNA dysregulation**: Aberrant overexpression of oncogenic miRNAs (oncomiRs like miR-21) or downregulation of tumor suppressor miRNAs (e.g., let-7, miR-34) drives tumorigenesis $\rightarrow$ **CORRECT**.
- All three statements **P, Q, and R** are correct.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Omits validated statement R.
- **Option (B) is INCORRECT**: Omits validated statement P.
- **Option (C) is INCORRECT**: Omits validated statement Q.
- **Option (D) [P, Q and R] is CORRECT**: All three oncogenic mechanisms are well-established.
**3. Final Answer**:
- **Correct Choice**: **D**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.