The answer is 12. An amino acid is coded by 3 nucleotide bases referred to as a codon. This genetic information is carried by the messenger-RNA and translated by ribosomes. A tRNA has an anticodon (sequences of 3 nucleotide bases) that are complementary of the respective codon on the mRNA. This is how th tRNA bring in the requisite amino acid for every codon on the mRNA.
