Question

Match the LIST-I with LIST-II

LIST-I Class of Mutagens	LIST-II  Examples
A. Alkylating agent	III. Mustard gas
B. Base analog	IV. 5-Bromouracil
C. Intercalating agent	I. Acridine Orange
D. Deamination agent	II. Nitrous acid

Choose the correct answer from the options given below:

• A. A-I, B - II, C - III, D - IV
• B. A-I, B - III, C - II, D - IV
• C. A-I, B-II, C - IV, D - III
• D. A- III, B - IV, C - I, D - II

Hint:

For mutagen questions, focus on the mechanism of action. 'Alkylating' adds alkyl groups, 'Base analog' mimics a base, 'Intercalating' inserts between bases, and 'Deamination' removes an amino group. Connecting the name to the mechanism helps in recalling examples.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The question requires matching different classes of chemical mutagens with their correct examples. A mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism.
Step 2: Detailed Explanation:
Let's analyze and match each class of mutagen in List-I:

A. Alkylating agent: These agents donate an alkyl group (e.g., -CH₃, -CH₂CH₃) to amino or keto groups in nucleotides. This alters base-pairing properties. Mustard gas is a classic example of an alkylating agent. Thus, A matches with III.

B. Base analog: These are molecules that are structurally similar to the normal purine and pyrimidine bases in DNA. They can be incorporated into DNA during replication and cause mispairing. 5-Bromouracil is an analog of thymine. Thus, B matches with IV.

C. Intercalating agent: These are flat, planar molecules that can insert themselves (intercalate) between the stacked base pairs of DNA. This insertion distorts the double helix and can lead to frameshift mutations during DNA replication. Acridine Orange is a well-known intercalating agent. Thus, C matches with I.

D. Deamination agent: These agents work by removing an amino group (-NH₂) from a nucleotide base. Nitrous acid (HNO₂) deaminates cytosine to uracil and adenine to hypoxanthine, causing incorrect base pairing. Thus, D matches with II.

Step 3: Final Answer:
The correct set of matches is A-III, B-IV, C-I, D-II, which corresponds to option (D).