Stem-loop structures in the transcript that encodes the leader peptide of the trp
operon (trpL) are partially responsible for regulating transcription of the operon. If
regions 2 and 3 of the leader pair, transcription continues through the operon. If
regions 3 and 4 pair, transcription terminates. Region 1 contains two consecutive Trp
codons. What do you expect will happen when tryptophan is absent?
A. Regions 1 and 2 will pair because the ribosome will pause at the Trp
codons in region 1.
B. Regions 2 and 3 will pair because the ribosome will pause at the Trp
codons in region 1.
C. Regions 2 and 3 will pair because the ribosome will translate through the
Trp codons in region 1 and enter region 2.
D. Regions 3 and 4 will pair because the ribosome will pause at the Trp
codons in region 1.
E. Regions 3 and 4 will pair because the ribosome will translate through the
Trp codons in region 1 and enter region 2.
I understand that the answer is C here. But what would be the case if Trp were present in the cell? Would it be D then? Also are these the only two scenarios that could occur here given the answer choices? My teacher did not cover any other scenarios. Thank you so much!
Stem-loop structures in the transcript that encodes the leader peptide of the trp
operon (trpL) are partially responsible for regulating transcription of the operon. If
regions 2 and 3 of the leader pair, transcription continues through the operon. If
regions 3 and 4 pair, transcription terminates. Region 1 contains two consecutive Trp
codons. What do you expect will happen when tryptophan is absent?
A. Regions 1 and 2 will pair because the ribosome will pause at the Trp
codons in region 1.
B. Regions 2 and 3 will pair because the ribosome will pause at the Trp
codons in region 1.
C. Regions 2 and 3 will pair because the ribosome will translate through the
Trp codons in region 1 and enter region 2.
D. Regions 3 and 4 will pair because the ribosome will pause at the Trp
codons in region 1.
E. Regions 3 and 4 will pair because the ribosome will translate through the
Trp codons in region 1 and enter region 2.
I understand that the answer is C here. But what would be the case if Trp were present in the cell? Would it be D then? Also are these the only two scenarios that could occur here given the answer choices? My teacher did not cover any other scenarios. Thank you so much!
Related textbook solutions
Related questions
Complete the Chart.
| Effect on Attentuation | Explanation | |
| Increasing the distance (number of bases) between the leader peptide gene and sequence 2. | ||
| Increasing the distance between sequences 2 and 3. | ||
| Removing sequence 4. | ||
| Changing the two trp codons in the leader pepetide gene to his codons | ||
| Eliminating the ribosome-binding site for the gene that enocodes the leader peptide. | ||
| Changing several nucleotides in sequence 3 so that it can base pair with sequence 4 but not with sequence 2. |
Options:
1) Attenuated by Trp
2) not attenuated by Trp
3) The translating ribosome is too far away to prevent 2:3 hairpin formation
4) The 2:3 hairpin stem and loop is less likely to form, allowing the 3:4 attenuator to form.
5) Sequence 4 is required for attenuator formation
6) Histidine levels now regulate production of Trp gene products.
7) The ribosome is not bound to the sensor site, so attenuation cannot occur.
8) Only the 3:4 attenuator stem and loop can form.
