ND STONY BROOK UNIVERSITY LOOSELEAF GENETICS: FROM GENES TO GENOMES
6th Edition
ISBN: 9781260406092
Author: HARTWELL, Leland, HOOD, Leroy, Goldberg, Michael
Publisher: Mcgraw-hill Education/stony Brook University
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Textbook Question
Chapter 16, Problem 20P
Six strains of E.coli (mutants 1–6) that had one of the following mutations (i–vi) affecting the lac operon were isolated.
i. deletion of lacY |
ii. oc mutation |
iii. missense mutation in lacZ |
iv. inversion of the lac operon (but not an inversion of the lacI gene) |
v. superrepressor mutation |
vi. inversion of lacZ, Y, and A but not lacI, P, o |
a. Which of these mutations would prevent the strain from utilizing lactose? |
b. The entire lac operon (including the lacI gene and its promoter) from each of the six E. coli strains was cloned into a plasmid vector containing an ampicillin resistance gene. Each recombinant plasmid was transformed into each of the six strains to create partial diploids. In analysis of these strains, mutant 1 was found to carry a deletion of lacY, so this strain corresponds to mutation i in the list above. Which of the other types of mutations would be expected to complement mutant 1 in these partial diploids so as to allow lactose utilization? |
c. In part (b), each strain was plated on ampicillin media in which lactose was the only carbon source. (Ampicillin was included to ensure maintenance of the plasmid.) Growth of the transformants is scored below (a + sign indicates growth, a − sign means no growth). Synthesis of β-galactosidase and permease are both required for growth on this medium. Results of this merodiploid analysis are shown here. Which mutant bacterial strain (1–6) contained each of the alterations (i–vi) listed previously? |
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A number of mutations affect the expression of the lac operon in E. coli. The
genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene
with normal function and "-" indicates a loss-of-function allele.) Please predict which
of the following strains would have the lowest beta-galactosidase enzyme activity,
when grown in the lactose medium.
OF POZY
Ort Ptot Z¹ Yt
Ort p²o+z¹Y+
Orpt ot zty
A number of mutations affect the expression of the lac operon in E. coli. The
genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene
with normal function and "-" indicates a loss-of-function allele.) Please predict which
of the following strains would have the highest beta-galactosidase enzyme activity,
when grown in the lactose medium.
O CAP+ r* p* o* z
O CAP* I P* o* z*
O CAP* r* P O* z*
O CAP I P* O z*
Answer the following questions:
1. Given the following genotypes, explain how the mutation (identified by a () superscript will affect E.
coli grown in lactose medium. Will the lac operon be on or off? Will there be a complete set of gene
products from the loc operon? What will be the implication of the missing gene product, if ever? Will the
cell be able to survive in the lactose medium or not?
a. p' oE Y
b. p'o Y
d. po v
Chapter 16 Solutions
ND STONY BROOK UNIVERSITY LOOSELEAF 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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- Strain P77 has a mutation in the lacO that prevents it from being bound by the lacI protein. Otherwise all other parts of the operon are functional. 1. Can strain P77 metabolize lactose if it is present? 2. If lactose is absent, will strain P77 transcribe its lac operon? 3. If lactose is present, will strain P77 transcribe its lac operon?arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the lowest beta-galactosidase enzyme activity, when grown in the lactose medium. Orpt o* z* r* Orpt ot z* Y OrptoztY Orrotzr OrPotz*Yarrow_forwardStrain 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. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lac operon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.arrow_forward
- Give the levels of Beta-galactosidase activity (high or low or zero) expected for the following partial diploids for the lac operon strains.arrow_forwardStrain P77 has a mutation in the lacO that prevents it from being bound by the lacI protein. Otherwise all other parts of the operon are functional. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lacoperon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.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
- Give all possible genotypes of a lac operon that produces, or fails to produce, B-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose present B-Galactosidase Lactose absent B-Galactosidase Permease Permease a. b. C. d. e. f. g. + I + II + + + | +Iarrow_forwardThe diagram below represents a hypothetical operon in the bacterium E. coli. The operon consists of two structural genes (A and B), which code for the enzymes “Aase" and "Base", respectively, and also includes P (promoter) and O (operator) regions as shown. A В When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes "Aase" and "Base" are both synthesized at a 50-fold higher rate than in the absence of X. (X has a molecular weight of about 200.) Which of the following statements is true of the operon described above? The region of the A gene that codes for the carboxyl-terminal amino acid of “Aase" is near the left end of the A gene. The P region contains nucleotide sequences to which the RNA polymerase holoenzyme (including the o subunit) binds specifically but which the core enzyme does not recognize. The addition of X to the growth medium causes a repressor protein to bind tightly to the O region. The mRNA copied from this operon will be covalently…arrow_forwardStrain X-23 has a mutation in the lacI gene resulting in a lacI protein that cannot bind DNA. Otherwise all other parts of the operon are functional. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lacoperon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restoredarrow_forward
- Geneticists isolated six trains of E. coli (strains 1-6) whose lac operons had one of the following mutations (a-f): a. deletion of lacY b. oº mutation c. missense mutation in lacz d. inversion of the lac operon (which does not include the lacl gene) e. superrepressor mutation f. inversion of lacZ, Y, and Z, but not lacl, P, o Focusing on the mutation in B: a. what is the state of the lac operon (on, off, inducible, or constitutive)? b. Provide an explanation using repressor, RNA pol, transcription, and the appropriate regulatory region of the operon. c. If a pDNA of another lac operon is inserted into the bacteria with a wild type/normal copy of the DNA, how would this impact the transcription of the original mutant in B?arrow_forwardGiven the following genotypes, explain, by answering the questions in each number, how the mutation (identified by a (-) superscript) will affect E. coli grown in lactose medium. Will there be a complete set ofgene products? (Yes/No) Will the lac operon be turnedon/off? Will the cell survive? (Yes/No) a. i + p + o + z - y + b. i + p - o + z + y + c. i + p + o - z + y +arrow_forwardThe symbols A, B, C, D, E represent all the components of the lac operon, excluding LacA. The symbols are not in the order of the lac operon. Minus and plus signs represent activity of lacZ or LacY in the absence or presence of IPTG. LacI+ or LacI-, and LacO+ or LacOC alleles were used. Which of the symbols represents each of the lac operon components?arrow_forward
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