Which of the following base pairings is incorrect in DNA?

• A. Cytosine pairs with Guanine
• B. Guanine pairs with Cytosine
• C. Adenine pairs with Thymine
• D. Thymine pairs with Guanine

Answer: (D)

Verified step by step guidance

1. Recall the standard base pairing rules in DNA, which are based on complementary hydrogen bonding between nitrogenous bases.
2. Identify the correct base pairs: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).
3. Understand that these pairings are specific and consistent, meaning A always pairs with T, and C always pairs with G.
4. Evaluate the given options by comparing each pairing to the standard rules to determine which one does not follow the correct pairing.
5. Conclude that the pairing 'Thymine pairs with Guanine' is incorrect because Thymine pairs with Adenine, not Guanine.