Question

In: Biology

Which of the following occurs as a result of an abundance of tryptophan in E. coli?

Which of the following occurs as a result of an abundance of tryptophan in E. coli?

A.The leader sequence is not transcribed.

B.The 5 trp genes (TrpA - TrpE) are not transcribed.

C.Stalling of the ribosome at trp codons in the leader sequence

D. The 5 trp genes (TrpA - TrpE) are transcribed, but not translated.

 

Solutions

Expert Solution

An abundance of tryptophan in E. coli inhibits the expression of trp-operon genes (stops the transcription). This mechanism is called repressible negative gene regulation.

The Trp operon is a negative repressible feedback mechanism. The repressor for the trp operon is produced by the trpR gene situated upstream to the promoter. trpR gene is expressed continually at a low level. This produces a monomer of repressor proteins, which are in an inactive state.

When tryptophan is present, these monomers combine to form tetramers and combine with tryptophan; this causes a conformation (in the repressor) that allows the repressor to bind the operator. So it prevents the RNA polymerase from binding and transcribing the operon, so tryptophan is not produced from its precursor. When tryptophan is absent, the repressor is in its inactive conformation and cannot bind the operator, so transcription continues to produce tryptophan.

When the tryptophan levels are low, the O site (operator site) of the trp operon is not occupied by repressor protein; repressor proteins are also not occupied by tryptophan due to low levels. This will activate transcription of the Trp operon.

Attenuator RNA has four short sequences 1-4, forming 3 distinct secondary structures: 1-2, 2-3, or 3-4. The formation of a 2-3 stem-loop structure works as an antiterminator form, while a 3-4 stem-loop works as a terminator form.

The production of a protein from an mRNA sequence is known as translation. Ribosomes bind to mRNA and recruit tRNA molecules bound with tRNA specific amino acids. These tRNA have anticodons that are complementary to the codon sequence of mRNA. Ribosomes from peptides bonds between amino acids, thus forming a peptide-protein sequence.

The adjoined picture below shows repression of trp-operon under high tryptophan concentration.

Thus, the correct option is (B) The 5 trp genes (TrpA -TrpE) are not transcribed.

 


The correct option is (B) The 5 trp genes (TrpA -TrpE) are not transcribed.

Related Solutions

In an experiment, E. Coli that are auxotrophic for methionine, tryptophan, and adenine biosynthesis are grown...
In an experiment, E. Coli that are auxotrophic for methionine, tryptophan, and adenine biosynthesis are grown on petri dishes containing rich media with all of these nutrients. The bacteria grow into normal colonies. The same bacteria are plated onto media that is lacking those 3 nutrients (minimal media) and no growth is observed. A second strain of E. Coli which is auxotrophic for histodine, and leucine is also able to grow on rich media but not minimal media. After mixing...
Operon. A particular E. Coli strain has a mutation in the operator of the tryptophan operon....
Operon. A particular E. Coli strain has a mutation in the operator of the tryptophan operon. How would you expect it would affect the functioning of the operon and the metabolism of the cells? What would happen if the trp operon had a mutation in the: 1. Promoter region? 2. Repressor gene (domain binding to tryptophan)? 3. Leader sequence TGGTGG? 4. Region 3 of Leader mRNA?
Your lab is studying gene expression of the tryptophan operon in the bacterium E. coli. In...
Your lab is studying gene expression of the tryptophan operon in the bacterium E. coli. In order to facilitate this study, you have cloned the Trp-operon, excised the five coding genes (TrpA, B, C, D, and E), and replaced them with a copy of the reporter gene GFP (green fluorescent protein). The resulting recombinant DNA was inserted into an F' plasmid, and used to transform a number of different strains of E. coli. For each of the scenarios listed below,...
The E. coli trp operon encodes proteins involved in the biosynthesis of the amino acid tryptophan....
The E. coli trp operon encodes proteins involved in the biosynthesis of the amino acid tryptophan. Control of trp operon expression is mediated by two distinct regulatory mechanisms. Describe these two regulatory mechanisms in detail. Note Please give detail and comprehensive answer .
Which of the following statements is TRUE? E. coli sigma factors all recognize one E. coli...
Which of the following statements is TRUE? E. coli sigma factors all recognize one E. coli gene Prokaryotic mRNAs contain sequences for sigma factor binding mRNA in both E. coli and humans are translated with the same translation machinery E. coli sigma factors all bind to the core RNA polymerase mRNA always contains the nucleotide sequence encoding just one protein
Which of the following is required for an insertion sequence element in E. coli to be...
Which of the following is required for an insertion sequence element in E. coli to be able to transpose? A gene for reverse transcriptase and long terminal repeats A gene for reverse transcriptase and inverted repeats A gene for transposase and inverted repeats A gene for transposase and long terminal repeats A gene for DNA polymerase and long terminal repeats Which type of deletions and/or insertion would not lead to frameshift mutations? A deletion that removes only a single amino...
Explain how the replication of the lagging strand occurs in E. coli. Include a description of...
Explain how the replication of the lagging strand occurs in E. coli. Include a description of the role of each of the key enzymes involved.
Which of the following might be used by an E. coli cell to directly modify its...
Which of the following might be used by an E. coli cell to directly modify its metabolic activities through genetic control in response to nutrient availability? Nuclear pore inhibition The lac operon Protein targeting to the endoplasmic reticulum The spliceosome
Which of the following statements regarding ribosomes in E. coli are correct? they consist of two...
Which of the following statements regarding ribosomes in E. coli are correct? they consist of two separate subunits they are composed of RNA and proteins they read mRNA in a 3' → 5' direction the small subunit consists of two rRNA molecules they are responsible for synthesizing proteins in cells
20. Which of the following occurs as a result of the neural tube defect? a. Anencephaly...
20. Which of the following occurs as a result of the neural tube defect? a. Anencephaly b. Holoprocencephaly c. Microcephaly d. Syringomyelia e. Corpus callosum agenesis 21. Vascular disease involving the aorta, carotid and ophthalmic arteries in elderly patients, which of the following? a. Wegener granulomatosis b. Takayasu disease c. Polyarteritis nodosa d. Kawasaki disease e. Giant cell arteritis 22. What is the inflammatory bowel disease characterized by the development of pseudopolyps with mucosal regeneration and the development of pseudopolyps...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT