Genetics: From Genes to Genomes, 5th edition
5th Edition
ISBN: 9780073525310
Author: Leland H. Hartwell, Michael L. Goldberg, Janice A. Fischer, Leroy Hood, Charles F. Aquadro
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 15, Problem 18P
| a. The original constitutive operator mutations in the lac operon were all base changes in o1. Why do you think mutations in o2 or o3 were not isolated in these screens? |
| b. Explain how a mutagen that causes small insertions could produce an oc mutation. |
| c. Would the oc mutation described in part (b) be sensitive to laclS? Why or why not? |
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a. The original constitutive operator mutations in thelac operon were all base changes in o1. Why doyou think mutations in o2 or o3 were not isolated inthese screens?b. Explain how a mutagen that causes small insertions could produce an ocmutation.c. Would a strain with one of the ocmutations described in part (b) and also a lacIS mutation be ableto make β-galactosidase either in the presence orabsence of inducer? Explain
. a. How many ribosomes are required (at a minimum)for the translation of trpE and trpC from a singletranscript of the trp operon?b. How would you expect deletion of the two tryptophan codons in the RNA leader to affect theexpression of the trpE and trpC genes?
Consider 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 control
Chapter 15 Solutions
Genetics: From Genes to Genomes, 5th edition
Ch. 15 - For each of the terms in the left column, choose...Ch. 15 - The following statement occurs early in this...Ch. 15 - One of the main lessons of this chapter is that...Ch. 15 - All mutations that abolish function of the Rho...Ch. 15 - The promoter of an operon is the site to which RNA...Ch. 15 - You are studying an operon containing three genes...Ch. 15 - Prob. 7PCh. 15 - You have isolated two different mutants reg1 and...Ch. 15 - Bacteriophage , after infecting a cell, can...Ch. 15 - Mutants were isolated in which the constitutive...
Ch. 15 - For each of the E. coli strains containing the lac...Ch. 15 - For each of the growth conditions listed, what...Ch. 15 - For each of the following mutant E. coli strains,...Ch. 15 - Maltose utilization in E. coli requires the...Ch. 15 - Seven E. coli mutants were isolated. The activity...Ch. 15 - Prob. 16PCh. 15 - Six strains of E.coli mutants 16 that had one of...Ch. 15 - a. The original constitutive operator mutations in...Ch. 15 - Prob. 19PCh. 15 - Figure 15.16 on p. 525 shows that in the lac...Ch. 15 - Why is the trp attenuation mechanism unique to...Ch. 15 - a. How many ribosomes are required at a minimum...Ch. 15 - The following is a sequence of the leader region...Ch. 15 - For each of the E. coli strains that follow,...Ch. 15 - One mechanism by which antisense RNAs act as...Ch. 15 - For each element in the list that follows,...Ch. 15 - Great variation exists in the mechanisms by which...Ch. 15 - Many genes whose expression is turned on by DNA...Ch. 15 - Prob. 29PCh. 15 - The E.coli MalT protein is a positive regulator of...Ch. 15 - Prob. 31PCh. 15 - To find genes that are turned on or off in...Ch. 15 - Prob. 33PCh. 15 - Prob. 34PCh. 15 - Prob. 35PCh. 15 - The researchers who investigated bioluminescence...Ch. 15 - Prob. 37PCh. 15 - Quorum sensing controls the expression of...
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- 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:arrow_forward. Suppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.]a. Growth on medium in which the only carbonsource was lactose.b. Colony color in medium containing glycerol as theonly carbon source, X-gal, and IPTGarrow_forward. Partial diploid forms of E. coli were created, each of which contained a com- plete lactose operon at its normal chromosomal site and the regulatory se- quences only (laci, P laco) on a plasmid. Predict the effect of each mutation on the activity of B-galactosidase before and after the addition of inducer. Use -, +, or ++ to indicate approximate activity levels. Briefly explain the basis for each of your predictions.arrow_forward
- Operons A. Draw a schematic of the lac operon when glucose is low and lactose is high in the cell’s environment. B. Draw a schematic of the trp operon when tryptophan levels in the environment are low. C. What is the lux operon and how is affected by quorum sensing?arrow_forwardSuppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.] Colony color in medium containing glycerol as theonly carbon source and X-gal, but no IPTG.d. Colony color in medium containing high levels ofglucose as the only carbon source, X-gal, andIPTG.e. Colony color in medium containing high levels ofglucose as the only carbon source and X-gal, butno IPTGarrow_forward. 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 prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTRarrow_forward
- Strain ROFL4 has a premature stop mutation in the lacZ gene, resulting in a nonfunctional b-galactosidase. Otherwise all other parts of the operon are functional. 1. Can strain ROFL4 metabolize lactose if it is present? 2. If lactose is absent, will strain ROFL4 transcribe its lac operon? 3. If lactose is present, will strain ROFL4 transcribe its lac operon?arrow_forward4) Suppose you have an E. coli in which the gene that codes for the lac repressor protein has been mutated in such a way that the protein produced can bind to both lactose and DNA (at its specific binding site in the lac operon promoter) simultaneously. What effect, if any, would this have on regulation of expression of the lac operon? Briefly (1 sentence) explain why you would predict the effect or lack of effect this mutation would have.arrow_forward. 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 alaninearrow_forward
- The 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_forwardAnother class of suppressor mutations, not describedin the chapter, are mutations that suppress missensemutations.a. Why would bacterial strains carrying such missense suppressor mutations generally grow moreslowly than strains carrying nonsense suppressormutations?arrow_forwardate) DEFINE what is an Operon, and compare and contrast regulation of the LAC Operon and the TRP Operon. When is each turned ON or OFF? A. DRAW each operon in the PRESENCE of its own ligands (signal molecules). B. What controls the activity of the regulatory proteins involved? · Be sure to describe and show both POSITIVE and NEGATIVE regulation where appropriate. C. Explain HOW each type of control system is appropriate for an operon encoding either catabolic or anabolic enzymes.arrow_forward
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