2. PRESENTATION
ON
GENETIC CODE
Department of Genetics & Plant Breeding
Allahabad School of Agriculture
Sam Higginbottom Institute of Agriculture, Technology & Sciences,
(Deemed-to-be-University)
Allahabad-211007
DR. G. R. LAVANYA
Dept.of Genetics & Plant Breeding
ASHOK K. CHOUDHARY
ID NO. - 15MSCGPB024
3. INTRODUCTION
GENETIC CODE:-“Genetic code explains the
mechanism by which information is stored in
living organisms.”
CODON:-“A set of three nucleotide bases
constitutes.”
4. CONT…..
The genetic code consists of 64 triplets of
Nucleotides. These triplets are called codons.
The information in DNA is in the form of triplet
codons.
It is first transcribed in to RNA and than in to
proteins.
Every triplet codon in the DNA specifies one
amino acid in the protein.
5. First elucidation of CODON was done by
Marshall Nirenberg and Heinrich j.Matthaei in
1961.
6. TYPES OF CODON
The codons are of two types:-
1. Sense codon:- Those codons that code for amino
acids are called sense codons.
There are 61 sense codons in the genetic code
which code for 20 amino acids.
2.Signal codons:- Those codons that code for
signals during protein synthesis are know as
signal codons.
7. cont…..
These are AUG,UAA,UAG and UGA.
Signal codons are of two types:-
A. Start codons:- AUG(methionine)
B. Stop codons:- UAA,UAG and UGA. These
were earlier known as Non-sense codons.
11. PROPERTIES OF GENETIC CODE
1. The code is Triplet.
2. The code is Universal.
3. The code is Commaless.
4. The code is Non-overlapping.
5. The code is Non-ambiguous(cleared).
6. The code is Redundant(excessive).
7. The code has Polarity(definite direction).
12. ANTICODONS
The base sequence of t-RNA which is pairs with
codon of m-RNA during translation is called
Anti-codon.
Codons are written in 5 to 3 direction, whereas
Anti-codons are usually written in 3 to 5
direction.
The number of t-RNA molecules{Anti-codons} is
always much lesser than codons in an organism.
13. WOBBLE HYPOTHESIS
The wobble hypothesis was proposed by Crick in
1966.
This hypothesis states that,“During translation,
only the first two bases of a codon must pair in
usual manner with the bases of t-RNA Anticodon.
The third base can pair in different way.”
