Question

A tRNA is charged with the amino acid phenylalanine.

1. At what end of tRNA is this amino acid attached?
2. What is the mRNA codon that codes for phenylalanine?
3. What is its anticodon?
4. Name the enzyme responsible for this attachment.

Answer 1

1. The amino acid is attached to the 3’ end of the tRNA molecule. Specifically, it binds to the hydroxyl group of the terminal adenine in the conserved CCA sequence (the acceptor stem).
2. The primary mRNA codon for phenylalanine is UUU (though UUC also encodes it due to the degeneracy of the genetic code).
3. For the codon UUU, the complementary anticodon on the tRNA is AAA. If the codon is UUC, the anticodon would be GAA.
4. The enzyme responsible for attaching the amino acid to its specific tRNA is phenylalanyl-tRNA synthetase. This enzyme ensures high fidelity by specifically recognizing both the amino acid phenylalanine and its corresponding tRNA.