Question

Which among these is not a pyrimidine?

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

Answer 1

The correct option is A Guanine

The nitrogenous bases are purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are thymine, uracil and cytosine. These ring structure are known as heterocylic as they are made of atoms of two element known as nitrogen and carbon. The purines are double ring structure while the pyrimidines are single ring made up of carbon and nitrogen. Purines pair with the pyrimidines by hydrogen bonds.

So, the correct answer is option A.