Genetic Code and its Co-relation with
Wobble - Hypothesis
● Consists of a “TRIPLET “, i.e. A sequence of 3 bases codes for a
particular amino acid .
There are 4³ or 64 possible combinations .
● Group of 3 bases coding for an amino acid in mRNA is called a
● Degenerate : An amino acid can be coded for by more than
one codon. Anti codon shows Wobble .
● Unambiguous : Each codon indicates a single , specific
amino acid .
● Non-overlapping : When translated , the reading frame is
advanced 3 bases at a time .
● The base sequence is read from a fixed point , without any
● Out of 64 codons , 61 codons specify amino acid , while remaining 3
are nonsense or stop codons.
● The code is degenerate - except for Trp and Met,each amino acid is
coded by two or more codons .
● Codons are recognized by aminoacyl-tRNAs.
● Aminoacyl-tRNAs activate the amino acid for transfer to peptide
● Aminoacyl-tRNA synthetases does the critical job : linking the right
amino acid with "cognate" tRNA
amino acid + ATP → aminoacyl-AMP + Ppi
aminoacyl-AMP + tRNA → aminoacyl-tRNA + AMP
Sum of 1 and 2:
amino acid + tRNA + ATP → aminoacyl-tRNA + AMP + PPi
Wobble in the anti codon :
● In 1966, Francis Crick ,proposed “the Wobble
hypothesis”.According to this hypothesis, only the first two
bases of the codon have a precise pairing with the bases of the
anticodon of mRNA, while the pairing between the third bases
of codon and anticodon may Wobble (non specific).
● The pairing between the first two bases is normal, while
between G and U is against the normal pairing pattern. This
unusual bonding between G and U is called Wobble pairing.
● Inosine is the fifth base in the anti codon.
● Inosine arises through enzymatic modification of adenine by
ADAR-Adenosine Deanimase RNA specific .
● Inosine is commonly found in tRNAs and is essential for proper
translation of the genetic code in wobble base pairs.
● Advantage of wobble: dissociation of tRNA from mRNA is faster