Multiple Choice
In the context of translation, what is the primary function of ribosomes in a cell?
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5. DNA to RNA to Protein
Translation
Multiple Choice
In translation, how does the ribosome know when to stop synthesizing a polypeptide?
A
The ribosome stops when the A site binds a tRNA carrying tryptophan, because tryptophan is the final amino acid in most proteins.
B
A stop codon (UAA, UAG, or UGA) enters the A site and is recognized by a release factor, which triggers hydrolysis of the polypeptide from the tRNA.
C
The ribosome stops when the Shine-Dalgarno sequence is reached, because it signals termination of elongation.
D
The ribosome stops when GTP is depleted, because elongation cannot proceed without GTP hydrolysis.
Verified step by step guidance1
Understand that during translation, the ribosome synthesizes a polypeptide chain by reading mRNA codons sequentially and matching them with corresponding tRNA molecules carrying amino acids.
Recognize that the ribosome has three sites: the A (aminoacyl), P (peptidyl), and E (exit) sites, where tRNAs bind during elongation.
Know that translation termination occurs not by an amino acid-carrying tRNA, but when a stop codon (UAA, UAG, or UGA) enters the A site of the ribosome.
Learn that stop codons do not code for any amino acid and are recognized by proteins called release factors, which bind to the A site instead of tRNA.
Realize that the binding of a release factor triggers hydrolysis of the bond between the polypeptide and the tRNA in the P site, releasing the newly synthesized polypeptide and causing the ribosome to disassemble.
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