Which nitrogenous base is found in mRNA but not in DNA?

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

Answer: (A)

Verified step by step guidance

1. Recall the four nitrogenous bases found in DNA: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
2. Recall the four nitrogenous bases found in RNA: Adenine (A), Uracil (U), Cytosine (C), and Guanine (G).
3. Note that RNA contains Uracil (U) instead of Thymine (T), which is present in DNA.
4. Understand that Uracil pairs with Adenine during RNA transcription, replacing Thymine's role in DNA.
5. Conclude that the nitrogenous base found in mRNA but not in DNA is Uracil.