Final answer:
The third base of the codon, known as the 'wobble' base, can be mismatched with an anticodon base on the tRNA according to the wobble rules.
Step-by-step explanation:
According to the wobble rules, the base of the codon that can be mismatched with an anticodon base on the tRNA is typically the third base. This is often referred to as the "wobble" base. In the codon-anticodon pairing, the first two bases of the codon form strong Watson-Crick base pairings with the anticodon, while the third base (wobble base) allows for more flexibility and can sometimes form non-standard base pairs with the anticodon. This flexibility explains how a single tRNA can recognize multiple codons that code for the same amino acid, despite variations in the third nucleotide position.