. 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. Mutation Before After (a) No mutations in either chromosomal or plasmid genes (b) A mutation in the plasmid operator, which abolishes its binding to repressor (c) A mutation in the chromosomal promoter, which reduces affinity of promoter for RNA polymerase by 10-fold (d) A lacI gene mutation in the chromosome, which abolishes binding of the lacl gene product to inducer (e) A lacī gene mutation in the plasmid, which abolishes binding of the repressor to the inducer (f) A chromosomal laco mutation, which abolishes its binding to repressor (g) A mutation in the gene for CRP, which abolishes its binding to cydlic AMP | | | |

. 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. Mutation Before After (a) No mutations in either chromosomal or plasmid genes (b) A mutation in the plasmid operator, which abolishes its binding to repressor (c) A mutation in the chromosomal promoter, which reduces affinity of promoter for RNA polymerase by 10-fold (d) A lacI gene mutation in the chromosome, which abolishes binding of the lacl gene product to inducer (e) A lacī gene mutation in the plasmid, which abolishes binding of the repressor to the inducer (f) A chromosomal laco mutation, which abolishes its binding to repressor (g) A mutation in the gene for CRP, which abolishes its binding to cydlic AMP | | | |

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 13TYU: INTERPRET DATA Develop a simple hypothesis that would explain the behavior of each of the following...

See similar textbooks

Similar questions

Considering the Lac operon in E. coli, and chose what the expression of Lac Y would be in: I) E. coli WT (wild type, everything is functional) II) E. coli whose lacI gene has been deleted. Each of the two strains is growing in culture flasks that contain high glucose and high lactose. (choose among ‘high expression; low expression; no expression’)
. 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
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
The symbols a, b, and c in the table below represent theE. coli lac system genes for the repressor (I ), the operator(O) region, and the β-galactosidase (Z), although notnecessarily in that order. Furthermore, the order inwhich the symbols are written in the genotypes is notnecessarily the actual sequence in the lac operon.Activity (+) or inactivity (−) of Z geneGenotype Inducer absent Inducer presenta- b+ c+ + +a+ b+ c- + +a+ b- c- - a+ b- c+/a- b+ c- + +a+ b+ c+/a- b- c- - +a+ b+ c-/a- b- c+ - +a- b+ c+/a+ b- c- + +a. Which symbol (a, b, or c) represents each of the lacgenes I, O, and Z ?b. In the table, a superscript minus sign on a gene symbolmerely indicates a mutant, but some mutant behaviorsin this system are given special mutant designations.Using the conventional gene symbols for the lac operon,designate each genotype in the table.
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. − + − +
Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and the CAP protein under the cellular conditions listed in the accompanying table. Lactose Glucose (a) - - (b) + - (c) - + (d) + +
Consider this strain of E. coli with lac operon alleles: IS pt o* z* y+ /T p* oCz- Y+ In a written response, briefly explain if beta-galactosidase AND permease will be expressed, and if so, will they be inducible or constitutive.
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
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.
Lactose permease is encoded by the lacY gene of the lac operon.Suppose a mutation occurred at codon 64 that changed the normalglycine codon into a valine codon. The mutant lactose permease isunable to function. However, a second mutation, which changescodon 50 from an alanine codon to a threonine codon, is able torestore function. Is each of the following terms appropriate or inappropriate to describe this second mutation?A. ReversionB. Intragenic suppressorC. Intergenic suppressorD. Missense mutation
In the: Mutation of the regulatory region for a repressor protein in the lac operon. Explain: (a) What is the process affected? (b) What is the Effect on the process? (c) Does it affect prokaryotes, eukaryotes or both?
It has been postulated that thiogalactoside transacetylase (LacA in the lactose operon) plays a role in detoxification by acetylating potentially hazardous -galactosides to prevent their absorption after they have diffused out of the cell. How would you put this idea to the test?