Which nitrogenous base is not found in DNA?

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

Answer: (B)

Verified step by step guidance

1. Recall the four nitrogenous bases found in DNA: adenine (A), guanine (G), cytosine (C), and thymine (T).
2. Understand that DNA is composed of these four bases, which pair specifically: adenine pairs with thymine, and guanine pairs with cytosine.
3. Recognize that uracil (U) is a nitrogenous base found in RNA, not DNA.
4. Compare the given options to the bases found in DNA and identify which one is not part of DNA's structure.
5. Conclude that uracil is the nitrogenous base not found in DNA, as it is replaced by thymine in DNA molecules.