Biology with Connect Access Card
10th Edition
ISBN: 9780077705701
Author: Raven, Peter
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 16, Problem 1S
You have isolated a series of mutants affecting regulation of the lac operon. All of these are constitutive, that is, they express the lac operon all the time. You also have both mutant and wild-type alleles for each mutant in all combinations, and on F′ plasmids, which can be introduced into cells to make the cell diploid for the relevant genes. How would you use these tools to determine which mutants affect DNA binding sites on DNA, and which affect proteins that bind to DNA?
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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.] 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 IPTG
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.
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.
The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).
The possible answers indicate with a ʺ+ʺ or a ʺ-ʺ whether β-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)Genotype F: I+ Oc Z-/ Fʹ I- O+ Z+
KEY:I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)
Chapter 16 Solutions
Biology with Connect Access Card
Ch. 16 - In prokaryotes, control of gene expression usually...Ch. 16 - Prob. 2UCh. 16 - In E. coli, induction in the lac operon and...Ch. 16 - The lac operon is controlled by two main proteins....Ch. 16 - In eukaryotes, binding of RNA polymerase to a...Ch. 16 - In eukaryotes, the regulation of gene expression...Ch. 16 - In the trp operon, the repressor binds to DNA a....Ch. 16 - Prob. 1ACh. 16 - Specific transcription factors in eukaryotes...Ch. 16 - Repression in the trp operon and induction in the...
Ch. 16 - Regulation by small RNAs and alternative splicing...Ch. 16 - Eukaryotic mRNAs differ from prokaryotic mRNAs in...Ch. 16 - In the cell cycle, cyclin proteins are produced in...Ch. 16 - A mechanism of control in E. coli not discussed in...Ch. 16 - You have isolated a series of mutants affecting...Ch. 16 - Examples of positive and negative control of...Ch. 16 - What forms of eukaryotic control of gene...Ch. 16 - The number and type of proteins found in a cell...
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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 highest beta-galactosidase enzyme activity, when grown in the lactose medium. CAP It P+ O`Z+ CAP+ I P+ O+ Zt CAP+ It P- O+ Z+ CAP+ It P+ 0+ Zarrow_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 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*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_forward
- The genotypes of five merozygote bacteria are shown below. In each set, the genotype of the lac operon on the chromosome is on the left side of the slash () and the genotype of the lac operon on the F' plasmid is on the right side of the slash. Which of the merozygote bacteria listed below would be able to make high quantities of B-galactosidase in the absence of lactose? Mark all the answers that are correct. O i p*o°z¯ y*A*/F'I$ p*oʻz*y*A* I* p* o*Z¯YA*/F'T P*O*z*y* A* I* P* o*z*Y* A* /F'T P*O*z*y* A* O 1* p*o*z° YA*/F'T P*o°z*y*A* 1S p*0°2¯Y¯AZET P*O*Z*Y*A*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_forwardExamine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genAarrow_forward
- If a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??arrow_forwardA mutant E. coli strain is isolated which does not ever produce the enzymes β-galactosidase or permease, irrespective of whether lactose is present or absent. If the normal wild-type genotype with respect to the lac operon can be represented as lacI+ lacP+ lacO+ lacZ+ lacY+, give three different mutant genotypes (list all 5 operon components in each case, do not consider partial diploids) which would result in the mutant phenotype described here.arrow_forwardThe genotypes of five merozygote bacteria are shown below. In each set, the genotype of the lac operon on the chromosome is on the left side of the slash (/) and the genotype of the lac operon on the F' plasmid is on the right side of the slash. Which of the merozygote bacteria listed below would be able to make high quantities of B-galactosidase in the absence of lactose? Mark all the answers that are correct. OIP*o*z* y*A*/F'I P oʻz*Y*A*. OI P o°z-Y*A*/F'IS P O*z*Y*A* nd of B * P*o*zY A /F'I P*o z*Y*A* erase e D I' P*o*z YA /F'I P*O z*Y* A* strand a NA poly should be 1S P*0°ZYA/FI P O*z*Y*A*arrow_forward
- For the given genotypes (associated with the lac operon in E. coli), indicate with a "+" or "-" whether functional B - galactosidase would be expected to be produced in the indicated conditions, assuming low glucose levels. B - galactosidase production Genotype No lactose With lactose a) I- O+ Z+ / F' I+ O+ Z+ b) IS O+ Z+/ F' I+ O+ Z+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_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. 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_forward
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