Parts A-C in the table show the genotypes for two partial diploid strains of the lac operon. Gene names have been simplified (i.e., LacZ is shown as Z). Alleles are shown using superscript notations. There are two copies of the operon, one line is the copy in the genome and the other line is in a plasmid. In the blanks, indicate the effect of the partial diploid strains' genotype on the expression of the structure gene specified in the header of the table. Choose "functional" if you expect that any amount of normal enzyme will be made, "nonfunctional" if you expect that transcription occurs but only the mutated enzyme is made, or "no transcription" if the structural gene is not transcribed. Assume glucose is absent. Genotype (A) (B) (C) I- P+ O+ Z+Y- I+ P+ O+ Z- Y+ I- P+ OC Z+Y- I+ P- O+ Z-Y+ IS P+O+ Z+Y- I+ P+ OC Z- Y+ Lacy Presence of Lactose? 1. [Select] 3. [Select] 5. [Select] > > < Absence of Lactose? 2. [Select] 4. [Select] 6. [Select] < > >

Parts A-C in the table show the genotypes for two partial diploid strains of the lac operon. Gene names have been simplified (i.e., LacZ is shown as Z). Alleles are shown using superscript notations. There are two copies of the operon, one line is the copy in the genome and the other line is in a plasmid. In the blanks, indicate the effect of the partial diploid strains' genotype on the expression of the structure gene specified in the header of the table. Choose "functional" if you expect that any amount of normal enzyme will be made, "nonfunctional" if you expect that transcription occurs but only the mutated enzyme is made, or "no transcription" if the structural gene is not transcribed. Assume glucose is absent. Genotype (A) (B) (C) I- P+ O+ Z+Y- I+ P+ O+ Z- Y+ I- P+ OC Z+Y- I+ P- O+ Z-Y+ IS P+O+ Z+Y- I+ P+ OC Z- Y+ Lacy Presence of Lactose? 1. [Select] 3. [Select] 5. [Select] > > < Absence of Lactose? 2. [Select] 4. [Select] 6. [Select] < > >

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 11TYU

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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. − + − +
Which of the following lac operon genotypes would allow for functional versions of all the structural enzymes of the lac operon to be expressed constitutively even in the absence of lactose? Group of answer choices I+ O+ Z+ Y+ A+ I- O+ Z- Y- A- I+ OC Z+ Y+ A+ IS O+ Z+ Y+ A+ I+ O+ Z- Y+ A+
For each of the E. coli strains containing lac operon alleles listed, indicate whether the strain is inducible, constitutive, or unable to express beta-galactosidase and permease. (P+ and P- are functional and nonfunctional promoters, respectively) I+ P+ o+ Z- Y+ / I+ P+ oc Z+ Y+ I+ P+ o+ Z+ Y+ / I- P+ oc Z+ Y- I+ P+ o+ Z- Y+ / I- P+ oc Z+ Y- I- P- o+ Z+ Y- / I+ P+ oc Z- Y+ IS P+ o+ Z+ Y+ / I- P+ o+ Z+ Y-
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.
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.
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)
Two closely linked open reading frames (ORFs) have been identified on the E. coli chromosome and they are predicted to encode genes sugX sugY which is involved in the catabolism (utilization) of a non-glucose sugar. In the figure below, the top line (with the big arrow) is the coding strand, and the bottom line is the non-coding (template) strand of the operon. Since the RNA sequence would be the “same” as the coding strand, please label (show the location of), in relation to the ORFs, the promoter(s) and 4 other genetic elements in this region that may be involved in the transcription and translation of sugX and sugY as well as the regulation of their expression. (Note: genetic elements are the regions of DNA or RNA.) If you are not comfortable with the coding strand of the DNA, feel free to draw the mRNA strand underneath and label the relevant features on the RNA strand, but the RNA strand must be aligned with the DNA strands in position and scale. Leader(s)/antileader(s) and…
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 mutant strain of E. coli has a premature stop mutation in the lacZgene, resulting in a non-functional b-galactosidase. Otherwise, all other parts of the operon are functional. Which component of an F' plasmid will restore normal regulation and function of the lac operon in the resulting partial diploid?
The 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?
Which of the following describes the lac operon in E. coli when lactose and glucose is present in the culture medium? Select one: a. CAP inactive and RNA polymerase does not completely bind to the promoter of the lac operon and transcription of lactose-metabolizing enzymes decreases. b. CAP is active and RNA polymerase binds completely to the promoter of the lac operon and transcription of lactose-metabolizing enzymes decreases. c. Catabolite activator protein (CAP) inactive and RNA polymerase does not completely bind to the promoter of the lac operon and transcription of lactose-metabolizing enzymes increases. d. CAP is active and RNA polymerase binds completely to the promoter of the lac operon and transcription of lactose-metabolizing enzymes increases.