In the structure of DNA, the nucleotide thymine (T) always pairs with which other nucleotide?

• A. Cytosine (C)
• B. Uracil (U)
• C. Guanine (G)
• D. Adenine (A)

Answer: (D)

Verified step by step guidance

1. Recall the base pairing rules in the DNA double helix structure, which are based on complementary hydrogen bonding between nucleotides.
2. Identify the four nucleotides in DNA: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
3. Remember that Adenine (A) pairs specifically with Thymine (T) through two hydrogen bonds, forming a stable base pair.
4. Note that Cytosine (C) pairs with Guanine (G), and Uracil (U) is found only in RNA, not DNA.
5. Conclude that thymine (T) always pairs with adenine (A) in the DNA structure.