In the context of DNA structure, which nucleotide base is not found in DNA?

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

Answer: (A)

Verified step by step guidance

1. Recall the four nucleotide bases that make up DNA: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).
2. Understand that DNA is composed of these four bases, where Adenine pairs with Thymine, and Guanine pairs with Cytosine.
3. Recognize that Uracil (U) is a nucleotide base found in RNA, not DNA.
4. Note that Uracil replaces Thymine in RNA, pairing with Adenine during RNA transcription.
5. Conclude that among the options given, Uracil is the nucleotide base not found in DNA.