Q.42

Match the following:

Options:

(A) P-5, Q-4, R-2, S-8

(B) P-6, Q-3, R-1, S-7

(C) P-4, Q-2, R-1, S-6

(D) P-1, Q-7, R-5, S-3

Introduction

Matching questions involving enzymes, regulatory proteins, and operons are frequently asked in molecular biology and biotechnology examinations. Solving them correctly requires understanding enzyme activity, molecular targets, and gene regulation mechanisms.
In this article, we systematically match items from Group I with their correct counterparts in Group II and explain why only one option is correct.

Step-by-Step Matching Explanation

P) Polynucleotide Kinase → 5′ End of DNA (5)

• Polynucleotide kinase transfers phosphate from ATP to the 5′-OH end of DNA or RNA

• Used in DNA end-labeling

✅ Correct match: P-5

Q) Fluoride → Enolase (4)

• Fluoride is a metabolic inhibitor

• It specifically inhibits enolase in glycolysis

✅ Correct match: Q-4

R) Ras → GTPase (2)

• Ras is a small G-protein

• It binds and hydrolyzes GTP

✅ Correct match: R-2

S) lac Operon → Positive and Negative Regulation (8)

• lac operon is regulated by:

  • Negative regulation (lac repressor)

  • Positive regulation (CAP-cAMP complex)

✅ Correct match: S-8

Correct Matching

P ⁣− ⁣5,  Q ⁣− ⁣4,  R ⁣− ⁣2,  S ⁣− ⁣8​

✅ Correct Answer

Option (A)

Explanation of All Options

Option (A): P-5, Q-4, R-2, S-8

✅ Correct
All matches are biologically accurate.

Option (B): P-6, Q-3, R-1, S-7

❌ Incorrect

• Polynucleotide kinase acts on 5′ end, not 3′

• Ras is a GTPase, not ATPase

Option (C): P-4, Q-2, R-1, S-6

❌ Incorrect

• Polynucleotide kinase does not inhibit enolase

• lac operon is not related to DNA ends

Option (D): P-1, Q-7, R-5, S-3

❌ Incorrect

• Polynucleotide kinase is not ATPase

• lac operon is not an enzyme

Quick Reference Table

Final Conclusion

Understanding enzyme specificity, signal transduction proteins, and gene regulation mechanisms makes such matching questions straightforward. The only option that correctly matches all components is:

Option (A)​