A geneticist is doing research to modify protein structures by inserting changed amino acids into polypeptide sequences. She incubates cutaneous fibroblasts in a medium containing fluorescently tagged lysine residues during the procedure. After many hours, she discovers that fibroblast aminoacyl tRNA synthetase "loads" lysine residues onto tRNA molecules carrying the anticodon UUU. In the figure below, which of the following residues is most likely attached to tRNA?

Question

Quizplus · Accepted Answer

Eductional Objective: The picture above depicts the "cloverleaf" secondary structure of transfer RNA (tRNA), a tiny, noncoding subtype of RNA responsible for delivering amino acids to the site of protein synthesis and inserting them at the appropriate positions into the developing polypeptide chain.
The acceptor stem of tRNA is formed by base matching 5'-terminal nucleotides with 3'-terminal nucleotides. It contains the CCA tail, which is inserted as a post-transcriptional alteration to the 3' end of tRNA and functions as an amino acid binding site. The enzyme responsible for "loading" the proper amino acid to the 3' terminal hydroxyl group of the CCA tail is aminoacyl tRNA synthetase. The acceptor stem aids in the identification of correct tRNA by the appropriate aminoacyl tRNA synthetase.

A Geneticist Is Doing Research to Modify Protein Structures by Inserting