DNA Components

What is DNA made of or components of DNA?

  • DNA is a polymer.
  • Monomers are deoxyribonucleotides (we will call nucleotides).
  • DNA components are
    • Nucleotides and Nucleosides
    • Nitrogen bases
    • Sugar
    • Phosphate

Nucleotides and Nucleosides

Description Nucleotides Nucleosides

Each nucleotide is made up of three parts – a sugar, a phosphate and a nitrogen base. [phosphate covalently bonded to 3’ or/and 5’ hydroxyl group(s)]

DNA contains four types of nucleotides. Type of nucleotide depends on nitrogen base.

Each nucleoside is made up of two parts – a sugar and a nitrogen base. [No phosphate]
Component Nitrogen base Name of Nucleotide Name of Nucleoside
Adenosine (A) Deoxyadenylate Deoxyadenosine
Thymine (T) Deoxyguanylate Deoxyguanosine
Guanine (G) Deoxycytidylate Deoxycytidine
Cytosine (C) Deoxythymidylate Deoxythymidine

Nitrogen bases

  • There are 4 different bases in a DNA molecule, two purines and two pyrimidines.
    • Purines – adenine and guanine
    • Pyrimidines – cytosine and thymine
  • Sequence of nitrogen bases determine what biological information is written in DNA strand which is used to for build and maintain an organism.
N-base group Purines Pyrimidines
Members Adenine and Guanine Cytosine and Thymine
Derivative of pyrimidines, two ringed structure One ringed structure
Larger than pyrimidines Smaller than purines
Base pairs adenine – thymine and cytosine – guanine


  • DNA contains Β – D 2’-deoxyribose sugar
  • Named 2’-deoxyribose as hydroxyl group at 2’ carbon is missing (as compared to ribose sugar)
  • It is pentose sugar, named so as it contains 5 carbons
  • Prefix D – refer the configuration of sugar, because of the presence of asymmetric carbon atom
  • Hydroxyl groups from 3’ and 5’ carbon link to phosphate group to build DNA backbone.

Phosphate (phosphoric acid)

  • Out of three reactive hydroxyl groups of the phosphoric acid, two are used for DNA backbone formation or DNA chain formation.
  • It links to 3’ carbon of one sugar and 5’ carbon of another one.
  • The third one gives the DNA an acidic property

To know structure of DNA go though page DNA double helix.