The importance of the stop codon UAG is that it
A) tells the DNA polymerase to stop replicating the chromosome.
B) tells the RNA polymerase to stop transcribing the chromosome.
C) tells the tRNA to stop transcribing the DNA.
D) tells the ribosome to stop translating the mRNA.
E) signals the end of the operon.

Question

Quizplus · Accepted Answer

The stop codon UAG (along with UAA and UGA) is responsible for instructing the ribosome to stop protein synthesis during translation. When a ribosome encounters a stop codon, it signals for the release of the finished protein and the dissociation of the ribosome from the mRNA molecule. Thus, option D is the correct answer. The other options are not accurate: A) the stop codon does not affect DNA replication because it is part of the genetic code and not involved in the replication process. B) UAG does not instruct RNA polymerase to stop transcription, as it primarily responds to promoter and terminator signals. C) tRNA molecules do not transcribe DNA but rather carry specific amino acids and match them to the codons on the mRNA molecule. E) While stop codons play a regulatory role in protein synthesis, they are not directly related to operons, which are sets of genes that are transcribed together.

The Importance of the Stop Codon UAG Is That It