2. INTRODUCTION
uNucleic acids are the organic materials present in all
organisms in the form of DNA and RNA.
uThe DNA structure defines the basic genetic make up of our
body as well as nearly all life on earth.
3. WHAT IS DNA?
u DNA is a group of molecules that is responsible for carrying and
transmitting the hereditary materials from parents to offspring.
u DNA is known as Deoxyribo Nucleic Acid. It has a unique molecular
structure. It is present on both prokaryotic and eukaryotic cells.
u DNA was first recognised by swiss biologist Johannes Friedrich
Miescher in 1869.
4. STRUCTURE OF DNA
• The structure of DNA is described as double
helix.
• It is a nucleic acid, which is made up of
nucleotides and each nucleotide composed of
sugar, phosphate group and nitreogenous
bases.
• The structure was discovered by James Watson
and Francis Crick.
• The nitreogenous bases are adenine, thymine,
guanine and cytosine.
5. u These four nitrogen bases pair together in the following way: adenine with
thymine and cytosine with guanine.
u Adinine and guanine form a pair of purines and thymine and cytosine form a
pair of pyrimidines.
u The two strands run in opposite direction and the strands are helically twisted.
u The pitch of the helix is 3.4nm and the distance between the two
consecutive base pair is 0.34nm.
u DNA coils up forming chromosomes and there are 23 pair of chromosomes
in our body.
6. FUNCTIONS OF DNA
u Replication process - Transmitting the hereditary materials from
parents to offspring.
u Have a crucial role in production of proteins.
u Takes part in cell division.
u Gene therapy.
