The rate of transcription of the trip operates in E. is controlled by both repre

Question

The rate of transcription of the trip operates in E. is controlled by both repression and attenuation. a) Diagram and explain repression and attenuation regulator mechanism for the trp operates when tryptophan is present and absent. b) What likely effect would deletion of the trpl region of the top operon have on top E-D-C-B-A in E. Call cells growing in the presence of tryptophan? You mutate the trpL sequence that the two UGG Trp codons at positions 54-56 and 57-60 such (refer to figure) in the m leader sequence were changed to GGG Gly codons. What would most likely happen to trp operon regulation when tryptophan is present and absent?

Explanation / Answer

a. The trp operon, found in E.coli bacteria, is a group of genes that encode biosynthetic enzymes for the amino acid tryptophan. The trp operon is expressed that is turned on when tryptophan is low and repressed that is turned off when they are high. The trp operon is regulated by the trp repressor. when bound to tryptophan, the trp repressor blocks the expression of operon. The trp operon includes five genes that encode enzymes needed for tryptophan biosynthesis, along with a promoter for RNA polymerase binding site and an operator binding site for repressor protein. The genes of the trp operon are transcribed as a single mRNA.

This stretch of DNA is recognised by a regulatory protein known as trp repressor. when repressor binds to DNA of the operator, it keeps the operon from being transcribed by physically getting in the way of RNA polymerase, the transcription enzyme. When tryptophan is high, it attaches to the repressor molecules and change their shape so they become active. A small molecule tryptophan, which switches a repressor into its active state is called a corepressor.

ON the other hand, when there is low tryptophan, the trp trpressor is inactive, because no tryptophan is available to bind tio and activate it. it does not attach to DNA or block transcription, and this allows the trp operon to be trancribed by RNA polymerase.

b. Deletion of the trpL region would result in he levels of the tryptophan biosynthetic enzymes in cells growing in the presence of tryptophan being increased ten fold because attenuation does not occur if this rgion is absent.

The attenuation of tryp operon will no longer controlled by tryptophan's presence or absence instead the attenuation of trp operon would now be contrlled by the presence or absence of Gly codons.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.