Select the incorrect state w.r.t. mutagens (a) 5 methyl cytosine and 5 hydroxymethyl cytosine are natural base analogues (b) 5-bromouracil is a structural analogueof thymine © 2-aminopurine is an artificial base analogue of guanine (d) Nitrous acid deaminates adenine to hypoxanthine which is complementary to thymine. (e) Guanine is coverted to xanthine by Nitrous acid which pairs with cytosine

Options

A. (b), (d), & (e)
B. (a) & (d)
C. (a), (d), & (e)
D. all except (e)

Answer

To solve the question regarding the incorrect statements about mutagens, let's analyze each option step by step:

1. **Statement (a)**: "5-methylcytosine and 5-hydroxymethylcytosine are natural base analogues."
- **Analysis**: This statement is incorrect. Natural base analogues typically include compounds like 5-bromouracil and 2-aminopurine, but 5-methylcytosine and 5-hydroxymethylcytosine are not classified as natural base analogues.
- **Conclusion**: This statement is incorrect.

2. **Statement (b)**: "5-bromouracil is a structural analogue of thymine."
- **Analysis**: This statement is correct. 5-bromouracil is indeed a structural analogue of thymine and can pair with adenine during DNA replication.
- **Conclusion**: This statement is correct.

3. **Statement (c)**: "2-aminopurine is an artificial base analogue of guanine."
- **Analysis**: This statement is correct. 2-aminopurine is known to act as an artificial base analogue of guanine and can pair with cytosine.
- **Conclusion**: This statement is correct.

4. **Statement (d)**: "Nitrous acid deaminates adenine to hypoxanthine which is complementary to thymine."
- **Analysis**: This statement is incorrect. While it is true that nitrous acid deaminates adenine to hypoxanthine, hypoxanthine is actually complementary to cytosine, not thymine.
- **Conclusion**: This statement is incorrect.

5. **Statement (e)**: "Guanine is converted to xanthine by nitrous acid which pairs with cytosine."
- **Analysis**: This statement is correct. Nitrous acid can convert guanine to xanthine, and xanthine can pair with cytosine.
- **Conclusion**: This statement is correct.

**Final Conclusion**: The incorrect statements are (a) and (d).