Which among the following is a Purine ?

Guanine

The correct answer is Option (2) -Guanine

Nitrogenous bases, also called nucleobases, are nitrogenous compounds that form an important part of the nucleotides. Nucleotides are building blocks of DNA and RNA that are composed of a sugar, nitrogenous base and a phosphate group. There are a total of five bases found in the DNA and RNA world, namely – Adenine (A), Cytosine (C), Guanine (G), Thymine (T) and Uracil (U).

Nitrogenous bases are especially important in biology because they are key components of nucleotides the building blocks of genetic information like DNA and RNA. Our genetic information holds all the instructions for our cells to build structures and to function in the body. Changes to the nitrogenous base sequences can have disastrous consequences for both the cell and the organism. These changes, known as mutations, are the cause of numerous genetic diseases, such as cancer.

Nitrogenous bases come in two forms, purines and pyrimidines. Purines are nitrogenous bases that have two rings fused together and pyrimidines are nitrogenous bases that only have one ring. In both cases, the ring or rings are made up of carbon and nitrogen atoms with hydrogen atoms or other elements or functional groups bound to the different carbon and nitrogen atoms.

Purine composes two out of four nucleobases both in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA):

• Adenine
• Guanine

Pyrimidines consist of the remaining bases in DNA and RNA –

• Uracil
• Cytosine
• Thymine