Question

Which of the following is not a pyrimidine nitrogen base?

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

Answer 1

The correct option is D

Guanine

The correct option is D.

Explanation for the correct option:

1. There are two types of nitrogenous bases, Purine and Pyrimidine.
2. During metabolism, the chemical compounds that create uric acid are purines.
3. Pyrimidine is an organic compound similar to pyridine. It consists of nitrogen at positions $1$ and $3$ on the ring.
4. Adenine and Guanine are the purine nitrogen bases; Cytosine and Thymine (Uracil in case of RNA) are pyrimidine bases.
5. So Guanine is not a pyrimidine base.

Final answer: Guanine is not a pyrimidine nitrogen base.