Which of the following statements regarding attenuation of the trp operon is NOT true?
A) It is controlled by alternative folding of the mRNA synthesized from the trpL region.
B) If the two tryptophan codons were changed to arginine codons the operon would no longer be sensitive to tryptophan levels but would instead be sensitive to arginine levels.
C) Translation of a trpL coding sequence into a 14- amino acid polypeptide (including the methionine of the start codon and two back- to- back tryptophan codons) is crucial to its function.
D) When tryptophan levels are low, the ribosome will occupy regions 1 and 2 after completing translation of the coding sequence, regions 3 and 4 will pair, and transcription will terminate.
E) When tryptophan levels are high, the formation of a 3- 4 stem loop followed by the poly- U string will prevent expression of the structural genes of the operon.

Question

Quizplus · Accepted Answer

Explanation: When tryptophan levels are low, the ribosome stalls at the tryptophan codons in region 1, allowing regions 2 and 3 to pair and form an antiterminator structure, not regions 3 and 4. This prevents the formation of the 3-4 terminator stem-loop, allowing transcription to continue, not terminate.

Which of the Following Statements Regarding Attenuation of the Trp