specific base pairing is essential because there are only few codons that calls for amino acids, if there is no specific pairing then it needs more than the codon that is already present so it makes it more complicated. there are 64 codons three of which are stop codon 
39 3 39
64 codons in one amino acid???
64 is the total number of codons, for different amino acids it varies from 1-6 codons. sorry ive misread your question
its ok thanks a lot