Question

Which base pairings account for wobble at the third codon-anticodon position?

Short answer

An anticodon with C or A in the third position can potentially pair only with its Watson-Crick complementary codon. If U or G occupies the third anticodon position, two codons can be understood. I at the third anticodon position can pair with U, C or A.

Step-by-step solution

Wobble hypothesis

By connecting structural insight with logical deduction, Crick proposed the wobble hypothesis to describe how a t-RNA can recognize different degenerate codons. He assumed that the first two codon-anticodon pairings have normal Watson-Crick geometry. There would be a wobble in the third anticodon position to permit limited conformational adjustments in the pairing geometry.

The base pairing that accounts for wobble at the third codon-anticodon position

The allowed pairings for the third codon-anticodon position can be given as:

An anticodon with C or A in the third position can potentially pair only with its Watson-Crick complementary codon. If U or G occupies the third anticodon position, two codons can be understood. I at the third anticodon position can pair with U, C, or A.