Final answer:
The region of tRNA complementary to a codon in mRNA is called the anticodon. Even if the tRNA is chemically modified, it will still recognize the mRNA codon based on its anticodon sequence, regardless of the amino acid it carries.
Step-by-step explanation:
The region of the tRNA that is complementary to a codon in mRNA is called the anticodon. The function of the anticodon is to match the corresponding codon on the mRNA strand during the process of translation in protein synthesis. If a tRNA is chemically modified and the amino acid bound is different from the one specified by its anticodon, it would still recognize the mRNA codon specified by the original anticodon sequence.
For instance, if an activated tRNA with the anticodon AAA is modified to carry a different amino acid than what is usually paired with AAA, during translation, this tRNA would still pair with the mRNA codon UUU. The enzymes responsible for attaching amino acids to tRNA molecules, called aminoacyl-tRNA synthetases, recognize specific tRNA structures, but they do not alter the anticodon. Therefore, the anticodon-codon recognition is based on the complementary base-pairing rules, not the carried amino acid.