Question

Which of the following is/are consequence(s) of nitrous acid (HNO(_2)) mediated deamination?

• A. ( Deamination of cytosine, adenine, and guanine )
• B. ( GC-to-AT transitions )
• C. ( AT-to-GC transitions )
• D. ( Addition of alkyl group to the bases )

Hint:

When studying DNA damage by chemical agents, it's crucial to distinguish between different types of modifications (e.g., deamination vs. alkylation) as they have different implications for mutagenesis and repair mechanisms.

Answer 1

The Correct Option is A, B, C

Nitrous acid, a deaminating agent, can alter the genetic information of DNA by converting nucleobases through the loss of amino groups. Analysis of Each Option: (A) Correct: Nitrous acid can deaminate cytosine to uracil, adenine to hypoxanthine, and guanine to xanthine, thereby changing their pairing properties. (B) Correct: The deamination of cytosine to uracil results in uracil pairing with adenine instead of guanine during DNA replication, leading to GC-to-AT transitions upon subsequent rounds of DNA replication. (C) Correct: Deamination of adenine results in hypoxanthine, which pairs with cytosine rather than thymine, potentially leading to AT-to-GC transitions upon DNA replication. (D) Incorrect: The addition of an alkyl group to bases is not a consequence of nitrous acid treatment; this change is more associated with alkylating agents, not deaminating agents like nitrous acid. Conclusion:
Explanation: Deamination induced by nitrous acid results in the alteration of base-pairing rules and can lead to point mutations in the DNA. This process underscores the mutagenic potential of chemical agents on genetic material.