Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 16, Problem 26P
| a. How many ribosomes are required (at a minimum) for the translation of trpE and trpC from a single transcript of the trp operon? |
| b. How would you expect deletion of the two tryptophan codons in the RNA leader to affect the expression of the trpE and trpC genes? |
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Students have asked these similar questions
a. What is the function of operons in bacterial gene regulation?
b. Describe how a bacterial operon can be regulated by repressible proteins (such as the tryptophan operon). Include in your description both the “on” and “off” states of the operon. Key elements of your diagram should include: Co-repressor, Genes, mRNA, Operator, Operon, Promoter, Repressor, RNA polymerase.
. Listed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes?
Q. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alanine
2) Attenuation of the trp operon is controlled by the formation of stem-loop structures in the mRNA
of the trpl region. The attenuation function can be disrupted by mutations that alter the sequence
of the repeat DNA regions 1-4 and prevent formation of the RNA stem loops. Describe the most
likely effects on attenuation of each of the following mutation under the conditions specified.
a. Mutation in region 1 and low levels of tryptophan:
b. Mutation in region 2 and low levels of tryptophan:
Mutation in region 2 and moderate levels of tryptophan (low enough to release the
repression but enough to allow the ribosome to NOT pause):
с.
d. Mutation in region 3 and low levels of tryptophan:
е.
Mutation in region 3 and moderate levels of tryptophan (low enough to release the
repression but enough to allow the ribosome to NOT pause):
f.
Mutation in region 4 and low levels of tryptophan:
Chapter 16 Solutions
Genetics: From Genes to Genomes
Ch. 16 - For each of the terms in the left column, choose...Ch. 16 - The following statement occurs early in this...Ch. 16 - One of the main lessons of this chapter is that...Ch. 16 - All mutations that abolish function of the Rho...Ch. 16 - The figure at the beginning of this chapter shows...Ch. 16 - The promoter of an operon is the site to which RNA...Ch. 16 - You are studying an operon containing three genes...Ch. 16 - You have isolated a protein that binds to DNA in...Ch. 16 - You have isolated two different mutants reg1 and...Ch. 16 - Bacteriophage , after infecting a cell, can...
Ch. 16 - Mutants were isolated in which the constitutive...Ch. 16 - Suppose you have six strains of E. coli. One is...Ch. 16 - The previous problem raises some interesting...Ch. 16 - For each of the E. coli strains containing the lac...Ch. 16 - For each of the following growth conditions, what...Ch. 16 - For each of the following mutant E. coli strains,...Ch. 16 - Maltose utilization in E. coli requires the...Ch. 16 - Seven E. coli mutants were isolated. The activity...Ch. 16 - Cells containing missense mutations in the crp...Ch. 16 - Six strains of E.coli mutants 16 that had one of...Ch. 16 - a. The original constitutive operator mutations in...Ch. 16 - In an effort to determine the location of an...Ch. 16 - Prob. 23PCh. 16 - The footprinting experiment described in Fig....Ch. 16 - Why is the trp attenuation mechanism unique to...Ch. 16 - a. How many ribosomes are required at a minimum...Ch. 16 - The following is a sequence of the leader region...Ch. 16 - For each of the E. coli strains that follow,...Ch. 16 - Prob. 29PCh. 16 - For each element in the list that follows,...Ch. 16 - Among the structurally simplest riboswitches are...Ch. 16 - Great variation exists in the mechanisms by which...Ch. 16 - Many genes whose expression is turned on by DNA...Ch. 16 - In 2005, Frederick Blattner and his colleagues...Ch. 16 - The E.coli MalT protein is a positive regulator of...Ch. 16 - Prob. 36PCh. 16 - Prob. 37PCh. 16 - Prob. 38PCh. 16 - Prob. 39PCh. 16 - Prob. 40PCh. 16 - Prob. 41PCh. 16 - The researchers who investigated bioluminescence...Ch. 16 - Prob. 43PCh. 16 - Quorum sensing controls the expression of...Ch. 16 - Scientists are currently screening a chemical...
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- . Listed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? Q. Deletions in region 3 of the mRNA 5′ UTRarrow_forwardConsider the lac operon of E. coli. Specifically, explain the following: a. Describe the overall chromosomal structure/organization of the operon, indicating the location and function of the regulatory regions and the structural genes. b. Is lac a catabolic or anabolic pathway? Explain. Is the operon inducible or repressible? Explain. c. Describe the mechanisms involved in negative control & positive controlarrow_forwardListed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? a. A mutation that prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTR b. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alanine c. A mutation that creates a stop codon early in region 1 of the mRNA 5′ UTR d. Deletions in region 2 of the mRNA 5′ UTR e. Deletions in region 3 of the mRNA 5′ UTR f. Deletions in region 4 of the mRNA 5′ UTR g. Deletion of the string of adenine nucleotides that follows region 4 in the 5′ UTRarrow_forward
- A number of mutations affect the expression of the lac operon in E. coli. Consider each genotype below and complete the table using “+” to indicate that the gene is expressed, and “−” to indicate that gene is not expressed.arrow_forwardThe lactose operon in E. coli comprises two structural genes and three regulatory components.a.State the name of each structural gene and describe its function: b.) State the name of each regulatory component and describe its functionarrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. The new lac strain of Escherichia coli are as shown below: P+O+Z+Y+A+// P+O+Z+Y+A¯ (i) Illustrate how lactose induces the gene expression in lac 1 $// I-. (ii) Explain the function of the lacP and laco in the bacterial operon.arrow_forward
- The lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. You are given a new strain of Escherichia coli with the following lac operon genotype: p+0°Z•Y*A +// P*O*Z*Y+ A- (i) Explain how the lac I gene affects gene expression. (ii) Explain the function of the lacP in the bacterial operon. (iii) Which part of the lac operon is cis-dominant? Explain.arrow_forward. Recall that the trp operon has a special leader sequence (trpL) between the operator and the structural genes that offers attenuation as a mechanism for regulation of gene expression. (A) Draw a diagram of a trpL region of the operon when tryptophan is abundant in the cell.Label the following features: the DNA, 5’ and 3’ polarity of the RNA, the regions 1, 2, 3,and 4 and poly-U of the RNA, the pair of Trp codons (UGG), the ribosome, and RNA-Pol,along with any stem-loop structure that would form under these conditions (B) In the above example, will the rest of the trp operon genes be expressed? Briefly describe your reasoning why or why not (C) The trp codons in region 1 of the trpL gene have mutated to cysteines (UGG to UGC). What will be the effect on attenuation gene regulation of the trp operon? Brieflyexplain your reasoning.arrow_forwardThe dlagram below represents the tryptophan operon with the trp leader MRNA transcript enlarged to represent the AUG transiation start codon, two consecutive tryptophan amino acld codons (UGGUGG), and 4 regions (1, 2, 3, and 4) that base pair to form different hairpin-loop structures in the MRNA leader region. What would happen in this MRNA leader region when cells encounter very low levels of tryptophan in Its environment? Leader region trpE trpD trpC trpB trpA DNA 5' 3' Transcription trp leader sequence mRNA UGGUGG (tryptophan codons) AUG UUUUUU 1 3 4. The translating ribosome would stall at the two tryptophan codons, causing the formation of a hairpin-loop botween regions 3 and 4 to promote transcription of the trp operon. The translating ribosome would stall at the two tryptophan codons causing formation of hairpin-loop between regions 2 and 3, which functions as an anti-lerminator of transcription The translating ribosome would stall at the two tryptophan codons causing formation…arrow_forward
- i onlyarrow_forwardTo characterize the promoter of the gadA operon you made a series of deletion mutants removing pieces of the promoter to see what would happen. The results are found below: gad promoter gada gadX gadz 450 +1 lacz activity transcription start site pH 2.0 pH 7.0 A gad promoter beta-galactosidase (lacZ) +++ 450 gad promoter beta galactosidase (lacZ) +++ +++ 300 +1 gad promoter beta galactosidase (lacZ) 150 D gad beta galactosidase (lacz) -450 150 E gad promoter beta-galactosidase (lacZ) -450 -300 Based on these results, what can you conclude about the gad promoter? O a. The promoter is only regulated by repression Ob. The promoter is regulated by a mix of activation and repression O c. The promoter is only regulated by activation O d. The promoter has multiple operators and multiple enhancersarrow_forwardWhat would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)arrow_forward
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