Wobble hypothesis

A wobble base pair is a G-U and I-U / I-A / I-C pair fundamental in RNA secondary structure. Its thermodynamic stability is comparable to that of the Watson-Crick base pair. Wobble base pairs are critical for the proper translation of the genetic code. The genetic code makes up for disparities in the number of amino acids (20) for codons (64), by using modified base pairs in the first base of the anti-codon. One important modified base is inosine which can pair with three bases: uracil, adenine, and cytosine.
See more at Wikipedia.org...

Hypothesis to explain how one tRNA can recognize two codons. The third base in the anticodon can pair with more than one bases. This is due to the degeneracy of the genetic code which results in more than one triplet codes for some amino acids.