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.

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.

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter14: Gene Regulation

Section: Chapter Questions

Problem 9TYU: A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous...

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A lac operon containing one mutation was cloned into a plasmid, which was introduced by transformation into a bacterium containing a wild-type lac operon. The three genes of the chromosomal operon were rendered noninducible in the presence of the plasmid. (a) What kind of mutation in the plasmid operon could have this effect? (b) Suppose the result of transformation was to cause the three plasmid lac genes to be expressed constitutively, at a high level. What type of plasmid gene mutation could have this result?
Give all possible genotypes of a lac operon that produces, or fails to produce, β-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose absent Lactose present β-Galactosidase Permease β-Galactosidase Permease a. − − + + b. − − − + c. − − + − d. + + + + e. − − − − f. + − + − g. − + − +
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)
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
. 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 IPTG
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??
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?
What experimental results would indicate that the mutation lacISlacIS is dominant to lacI+lacI+? In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a constitutive state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in an activated state in the presence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the presence of lactose.
You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site Say you don’t know which mutant has a defect in the site and which one has a mutation in the binding protein. To figure it out, you construct the two partial diploid strains (i and ii below), and you then assay the levels of the Emu1 and Emu2 proteins in these two strains. F’ (reg1- reg2+ emu1- emu2+) / reg1+ reg2+ emu1+ emu2- F’ (reg1+ reg2- emu1- emu2+) / reg1+ reg2+ emu1+ emu2- What proteins do you predict will be expressed for strains i and ii if reg2 encodes the regulatory protein and reg1 is the regulatory site?
Strain 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 restored
A strain of E. coli has the genotypes shown below at the lac operon, where I = regulator gene, P = promoter, O = operator, Z = βgalactosidase gene, and Y = permease gene. The superscript+ indicates a wild-type allele,c indicates a constitutive mutation, and− indicates a defective mutation. For each genotype, indicate whether the enzyme will be synthesized or not synthesized when lactose is present or absent by placing a + for synthesis occurring and a − for synthesis not occurring in the appropriate blank. Explain your reasoning for each answer.
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?