Question

Renata enzymatically conjugates a 14 C ‑labeled cysteine to a transfer RNA (tRNA), with a UGU anticodon. Then, she chemically modifies the cysteine group to alanine. Finally, she adds the altered aminoacyl‑tRNA to a protein‑synthesizing system containing normal components and a messenger RNA (mRNA) with the sequence 5 ′ − UUUUGCCAUGUUUGUGCU − 3 ′ .What is the sequence of the radiolabeled peptide Renata produces?

Answer 1

The radiolabeled peptide sequence produced in Renata's experiment is Phenylalanine-Alanine-Histidine-Valine-Alanine-Alanine, with alanine being the radiolabeled amino acid.

Step-by-step explanation:

The student's question pertains to the sequence of a radiolabeled peptide that is produced during a protein-synthesizing system. Renata has modified a cysteine-tRNA with an anticodon UGU to carry alanine instead of cysteine. When this tRNA is introduced into a ribosome along with the mRNA sequence 5′-UUUUGCCAUGUUUGUGCU-3′, it will participate in translation. We can break down the mRNA into codons (UUU, UGC, CAU, GUU, UGU, GCU) and, using the genetic code, find which amino acids they code for (Phenylalanine, Cysteine, Histidine, Valine, Cysteine, Alanine). However, since cysteine-tRNA was modified to carry alanine, every time the codon for cysteine (UGC or UGU) appears, alanine will be incorporated instead.

Therefore, the sequence of the radiolabeled peptide Renata produces will be Phenylalanine-Alanine-Histidine-Valine-Alanine-Alanine, with alanine being the radiolabeled amino acid.