Table 20-2 Diploid Analysis of Mutations Affecting the lac Operon Phenotype with Inducer Absent Phenotype with Inducer Present Line Number Genotype of Diploid Bacterium* B-galactosidase Permease B-galactosidase Permease * pt o+z+y+/t pt o+z+y+ * pt o+z Y+/+pt o+z+Y 1 2 *pt o+zY+/Ipt o*z*Y + 4 t pt o+zY+/* p+ &ʻz*Y + * pt o+zY*/Pp+ o+z*Y P = Piac 2016 E

Table 20-2 Diploid Analysis of Mutations Affecting the lac Operon Phenotype with Inducer Absent Phenotype with Inducer Present Line Number Genotype of Diploid Bacterium* B-galactosidase Permease B-galactosidase Permease * pt o+z+y+/t pt o+z+y+ * pt o+z Y+/+pt o+z+Y 1 2 pt o+zY+/Ipt ozY + 4 t pt o+zY+/ p+ &ʻzY + pt o+zY/Pp+ o+zY P = Piac 2016 E

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter16: Gene Expression

Section: Chapter Questions

Problem 9RQ: The a/a operon is an inducible operon that controls the production of the sugar arabinose. When...

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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. − + − +
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+
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
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…
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-
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+
Given 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 +
In a bacterial cell with the genotype I-: P+: O+: Z+: Y+: A+, which of the following expression patterns of the lac operon would you see? (All + signs designate functional units and - signs designate non-functional units) A. No expression of Z, Y and A under any environmental conditions. B. Z, Y and A would always be expressed. C. Z, Y and A would be expressed when lactose was present but not expressed if lactose is not present. D. Z, Y and A would be expressed in the absence of lactose, but not when lactose was present. E. None of the above.
The a/a operon is an inducible operon that controls the production of the sugar arabinose. When arabinose is present in a bacterium it binds to the protein AraC, and the complex binds to the initiator site to promote transcription. In this scenario, AraC is a(n). activator inducer repressor operator
Six strains of E. coli (mutants 1–6) that had one of thefollowing mutations (i–vi) affecting the lac operonwere isolated.i. deletion of lacYii. ocmutationiii. missense mutation in lacZiv. inversion of the lac operon (but not an inversion ofthe lacI gene)v. superrepressor mutationvi. inversion of lacZ, Y, and A but not lacI, P, oa. Which of these mutations would prevent the strainfrom utilizing lactose?b. The entire lac operon (including the lacI gene andits promoter) from each of the six E. coli strainswas cloned into a plasmid vector containing an ampicillin resistance gene. Each recombinant plasmidwas 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 thisstrain 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…
For the following E.coli genotype trpR- trpP+ trpO+ trpE- / trpR- trpP+ trpO+ trpE+ the production of the first enzyme (trpE) in the tryptophan operon is zero repressible constitutive inducible