Wobble or Fluctuating base:
Crick (1966) proposed Wobble Hypothesis. According to this hypothesis, the base in first position of anti-codon on tRNA is usually an abnormal base, like inosine, pseudouridine, tyrosine etc. These abnormal bases are able to pair with more than one type of nitrogenous base in the third position of the codon on mRNA. For example Inosine (I) can pair with A, C or U. this base is called Wobble base or fluctuating base
Wobble occurs at position 1 of the anti-codon and position 3 of the codon.
The wobble hypothesis states that the third position (3’) of the codon on mRNA and the first position (5’) of the anticodon on tRNA are bound less tightly than the other pair and therefore, offer unusual base combinations.
This phenomenon give rise to:
- The multiple codes for a given amino acid(degeneracy)
- Possible suppression of point mutations in the third base of the codon
- More easily removed deacylated tRNA during protein synthesis.
- Fewer tRNA molecules than expected.