Assertion : Base analogs induce transition.
Reason : Base analogs perform forbidden pairing.

Options

A. a.If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion, then mark (1)
B. b.If both Assertion and Reason are true ,but the Reason is not the correct explanation of the Assertion, then mark (2).
C. c.If Assertion is true, but Reason is false , then mark (3)
D. d.If both Assertion and Reason are false. , then mark (4)

Answer

### Step-by-Step Solution:

1. **Understanding Base Analogs**:
- Base analogs are chemical compounds that closely resemble the structure of nucleotide bases (adenine, thymine, cytosine, and guanine) found in DNA.
- Because of their similarity, they can substitute for these bases during DNA replication.

**Hint**: Remember that base analogs mimic the structure of DNA bases.

2. **Induction of Transitions**:
- A transition mutation is a type of point mutation where a purine is replaced by another purine (A ↔ G) or a pyrimidine is replaced by another pyrimidine (C ↔ T).
- When base analogs are incorporated into DNA, they can lead to incorrect base pairing during replication, resulting in transition mutations.

**Hint**: Focus on how the substitution of bases can lead to specific types of mutations.

3. **Understanding Forbidden Pairing**:
- Forbidden pairing refers to the incorrect pairing of bases that occurs when base analogs are present.
- For example, a base analog may pair with a base that it normally would not pair with, leading to mutations.

**Hint**: Consider how base analogs disrupt normal base pairing rules.

4. **Evaluating the Assertion and Reason**:
- The assertion states that base analogs induce transitions, which is true because they can cause mutations during DNA replication.
- The reason states that base analogs perform forbidden pairing, which is also true as it explains how these mutations occur.

**Hint**: Check if the reason logically supports the assertion.

5. **Conclusion**:
- Both the assertion and the reason are true, and the reason provides a valid explanation for the assertion. Therefore, the correct answer is that both statements are true, and the reason explains the assertion.

**Hint**: Look for connections between the assertion and reason to determine their relationship.

### Final Answer:
Both the assertion and the reason are true, and the reason explains the assertion.