Introduction

Nucleic acid is of two types in all living system.

• Deoxyribonucleic acid (DNA).
• Ribonucleic acid (RNA).

DNA is a genetic material in all living organisms except viruses.
RNA is a genetic material in riboviruses.

The DNA

• DNA is a long polymer of Deoxyribonucleotides.
• It is an acidic substance present in nucleus.
• It was first identified by friedrich meischer in 1869. He name it as Nuclein.
• Altmann found these substances to be acidic in nature hence he named it nucleic acid.
• The length of DNA is usually defined as numbers of nucleotides or a pair r of Nucleotides referred to as base pair (bp) present in it.

THE RNA

Ribonucleic acid
Single-stranded structure
RNA is a Polymer (Polynucleotide)
Monomer units: ribonucleotides

Structure Of Nucleotide

A nucleotide has three components :-

Pentose sugar
Phosphate group
Nitrogenous base.

There are two types of nitrogenous bases :-

• Purine :- adenine (A) and guanine (G)
• Pyrimidines :- Cytosine (c) and Thymine (T)

Cytosine is common in both DNA and RNA.
Thymine is present in DNA and uracil is present in RNA at the place of thymine.

Types of Linkge or Bond

N- glycosidic linkage
A nitrogenous base is linked to pentose sugar through N-glycosidic linkage to form a nucleoside.
Phosphoester linkage
Phosphate group is linked to 5’OH of nucleoside through phosphester linkage to form nucleotide.

Two nucleotides are linked through 3′-5′ Phosphodiester linkage to form a dinucleotide.