GENETIC CODE
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT-3: CENTRAL DOGMA AND GENETIC CODE .
DR. UTTAM KUMAR KANP
ASSISTANT PROFESSOR DEPARTMENT OF BOTANY
NARAJOLE RAJ COLLEGE
GENETIC CODE:
The nucleotide sequence, containing a set of 3
bases, of mRNA is called codons and each codon
is specific for one amino acid. Whereas the
genetic code is the sequence of nitrogenous
bases in mRNA molecules, which's information
for synthesis of protein molecules.
DISCOVERY OF GENETIC CODE:
A code of 3 nucleotide could code maximum of 4 3 =64 amino acids.
The Crick, Barnett, Brenner and Watts-Tobin (1961). Experiment first, demonstrate that code consist of 3-DNA bases.
Dr. H. G . Khorana (1965) identified the rest of the genetic code.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT-3: CENTRAL DOGMA AND GENETIC CODE .
Triplate codons of mRNA for amino acids.
ESSENTIAL FEATURE OF GENETIC CODE:
Triplet
Commaless
Non-overlapping
Ambiguity
Universality
Degeneracy
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TRIPLET
A codon of the modern genetic code comprises of 3 nitrogenous bases of mRNA in a specific sequence.
COMMALESS:
There is no comma between the adjacent codon.
NON OVERLAPPING:
Initially it was disturbing for some geneticists to thick of degeneracy in connection with genetic code.
Evidances have been gathered in support of non overlapping codon.
BOTANY: SEM-IV, PAPER-C8T: MOLECULAR BIOLOGY, UNIT-3: CENTRAL DOGMA AND GENETIC CODE .
AMBIGUITY:
A particular codon always codes for the same amino acid.
UNIVERSALITY:
The same genetic code is said to be present in all
kind of living organism.
INITIATION CODON:
A triplet of bases in mRNA with the sequence AUG (less commonly, GUG) that acts as a “Start” signal for TRANSLATION.
It marks the beginning of the massage for polypeptide chain.
AUG-it codes methionine.
• UAA, UAG ,UGA are stop codons.
TERMINATION CODON
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