Question

Under normal circumstances, protein synthesis terminates when__________:

a. the 3' end of the mrna enters the a site on the ribosome.
b. a stop codon enters the p site on the ribosome.
c. rho binds to the 3' end of the mrna causing it to drop off the ribosome.
d. a stop codon enters the a site on the ribosome.
e. more than one of the above answers is correct.

Answer 1

Protein synthesis ends when d. a stop codon reaches the A site on the ribosome, triggering the release of the newly formed protein and disassembly of the ribosome for future rounds of synthesis.

Step-by-step explanation:

Under normal circumstances, protein synthesis terminates when a stop codon enters the A site on the ribosome (option d).

Specifically, when any of the three stop codons (UAA, UAG, or UGA) reach the A site, they are recognized by release factors, which act to stop the translation process.

This involves the hydrolysis of the bond between the polypeptide chain and the last tRNA in the P site, causing the release of the newly synthesized polypeptide chain.

Consequently, the ribosome subunits then dissociate from the mRNA, allowing them to be recycled and potentially initiate another round of protein synthesis.