Question

Name the basic and fundamental unit of nucleic acids

• A. Nucleoside
• B. Nucleotide
• C. Pentose sugar
• D. Nitrogenous base

Answer 1

The correct option is B Nucleotide

Nucleic acids (DNA and RNA) are polymers of nucleotides.

The nucleotide is the basic fundamental unit of nucleic acids.

Nucleotide is made up of three components.
1. 5-carbon sugar (pentose sugar)
2. Nitrogenous base
3. Phosphate group

In case of RNA, ribose sugar is present and in DNA, deoxyribose sugar is present.

The nitrogenous bases are of two types: the purines and the pyrimidines.

Purines are adenine (A) and guanine (G), while the pyrimidines are thymine (T), cytosine (C) and uracil (U).

The purines in both DNA and RNA are adenine and guanine.

The pyrimidines in DNA are cytosine and thymine and in RNA, they are cytosine and uracil.

A nucleoside is formed when a nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage.

When a phosphate group is linked to 5' -OH of a nucleoside through phosphoester linkage, a nucleotide is formed.