Which base pairing occurs in DNA?

Which base pairing occurs in DNA?

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

Answer: (D)

DNA base pairing follows specific rules: adenine forms hydrogen bonds with thymine, and cytosine pairs with guanine. This pairing pattern keeps the DNA double helix uniform in width and is dictated by the shapes and hydrogen-bonding capacities of the bases. Adenine and thymine pair through two hydrogen bonds, while guanine and cytosine pair through three. So the correct pairing is adenine with thymine and cytosine with guanine. Choices proposing adenine with cytosine or guanine with thymine don’t align with the bonding geometry and are not correct.

DNA base pairing follows specific rules: adenine forms hydrogen bonds with thymine, and cytosine pairs with guanine. This pairing pattern keeps the DNA double helix uniform in width and is dictated by the shapes and hydrogen-bonding capacities of the bases. Adenine and thymine pair through two hydrogen bonds, while guanine and cytosine pair through three. So the correct pairing is adenine with thymine and cytosine with guanine. Choices proposing adenine with cytosine or guanine with thymine don’t align with the bonding geometry and are not correct.