Which base pairs with Thymine?

Which base pairs with Thymine?

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

Answer: (A)

In DNA, base pairing is determined by hydrogen bonding and the need to keep the two strands the same width. Adenine forms two hydrogen bonds with thymine, making them a stable complementary pair. This pairing also fits the overall geometry of the double helix, since purines (adenine) pair with pyrimidines (thymine) to maintain a consistent helix diameter. Cytosine pairs with guanine, using three hydrogen bonds, which is a different interaction and helps balance the overall stability of the DNA. Thymine does not pair with cytosine or guanine. In RNA, thymine is replaced by uracil, which pairs with adenine in the same pairing logic.

In DNA, base pairing is determined by hydrogen bonding and the need to keep the two strands the same width. Adenine forms two hydrogen bonds with thymine, making them a stable complementary pair. This pairing also fits the overall geometry of the double helix, since purines (adenine) pair with pyrimidines (thymine) to maintain a consistent helix diameter.

Cytosine pairs with guanine, using three hydrogen bonds, which is a different interaction and helps balance the overall stability of the DNA. Thymine does not pair with cytosine or guanine. In RNA, thymine is replaced by uracil, which pairs with adenine in the same pairing logic.