Microbiology: An Evolving Science (Fourth Edition)
4th Edition
ISBN: 9780393615098
Author: John W. Foster, Joan L. Slonczewski
Publisher: W. W. Norton & Company
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Chapter 12, Problem 3TQ
Summary Introduction
To review:
The effect of the following conditions: when the strain is grown in lactose, the strain is grown without lactose, the lacI gene is deleted, and the lac operator is eliminated.
Introduction:
Lac operon is required for the transport and metabolism of lactose. In the absence of glucose, it allows for the effective digestion of lactose. They are used in several bacterial-based selection techniques as a reporter gene. Lac operon is regarded to be the first genetic regulatory mechanism and also an example of prokaryotic gene regulation.
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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 the trp operon, if a mutation occurred in the gene for the repressor so that it could bind to the operator even in the absence of tryptophan____________.
a) the inducer cannot bind trpO, so operon gene transcription occurs
b) the active repressor cannot bind trpO, so operon gene transcription is attenuated
c)the active repressor binds tpO, so operon gene transcription is always repressed
d) the repressor binds the corepressor, and operon gene transcription occurs.
In the presence of tryptophan, and a mutation in the allosteric domain that abolishes tryptophan binding______.
a) the active repressor cannot bind trp), so operon gene transription is attenuated
b) the inactive repressor cannot bind trpO, so operon gene transcription occurs]
c) the active repressor binds trpP, so operon gene trasncription is repressed, the inducer cannot bind trpO, so gene transcription occurs
d) the repressor binds to the corepressor, and an operon gene transcription occurs
Chapter 12 Solutions
Microbiology: An Evolving Science (Fourth Edition)
Ch. 12.1 - Prob. 1TQCh. 12.1 - Prob. 2TQCh. 12.1 - Prob. 3TQCh. 12.1 - Prob. 4TQCh. 12.2 - Prob. 1TQCh. 12.2 - Prob. 2TQCh. 12.2 - Prob. 3TQCh. 12.3 - Prob. 1TQCh. 12.4 - Prob. 1TQCh. 12.4 - Prob. 2TQ
Ch. 12.5 - Prob. 1TQCh. 12 - Prob. 1RQCh. 12 - Prob. 2RQCh. 12 - Prob. 3RQCh. 12 - Prob. 4RQCh. 12 - Prob. 5RQCh. 12 - Prob. 6RQCh. 12 - Prob. 7RQCh. 12 - Prob. 8RQCh. 12 - Prob. 9RQCh. 12 - Prob. 10RQCh. 12 - Prob. 11RQCh. 12 - Prob. 12RQCh. 12 - Prob. 13RQCh. 12 - Prob. 14RQCh. 12 - Prob. 15RQCh. 12 - Prob. 1TQCh. 12 - Prob. 2TQCh. 12 - Prob. 3TQ
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- 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.arrow_forwardA 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 nonin- ducible 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?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_forward
- The map of the lac operon is shown below. Consider the following examples that include both haploids and partial diploids and explain in each scenario whether the repressor can bind and regulate expression and whether or not the lac operon is expressed. For partial diploids the plasmid is indicated by the F’. I+ O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ I+ Oc Z+ Y+arrow_forwardThe lac operon has 4 genes, I, Z, Y and A. For each scenario, tell me the result of the mutation, what would happen if this mutant was in the presence of lactose and why. A) Lac I is mutated/not functional - B) Lac Y is mutated/not functional -arrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. You are given a new strain of Escherichia coli with the following lac operon genotype: p+0°Z•Y*A +// P*O*Z*Y+ A- (i) Explain how the lac I gene affects gene expression. (ii) Explain the function of the lacP in the bacterial operon. (iii) Which part of the lac operon is cis-dominant? Explain.arrow_forward
- 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.arrow_forwardImagine that a new strain of E. coli is discovered, and it contains the following novel genetic region including the lacI gene and the lac operon: *see image* Upstream of the promoter associated with the lac operon, there is a new operator element "Oν" (O-"nu"). This new operator has high sequence homology to O1, the DNA element that is bound with the highest affinity by the lac repressor. What would be the impact of this new genetic element regarding behavior of the operonin the absence (vs. the presence) of lactose and allolactose? Answer in terms of the protein levels of the lac repressor, as well as the proteins encoded by the genes lacZ/Y/A in the downstream region of the operon. Remember that proteins, once expressed/generated, will not persist forever, and that they have a natural lifetime (ending when they are degraded by the cell).arrow_forwardDescribe what would happen to the lac operon in a low-lactose environment and in a high lactose environment. a) How will each of these environments affect gene expression? b) What would happen to the repressor in each case? c) How will each of these environments affect RNA polymerase?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_forwarda) State the functions of the subunits of RNA polymerase and describe transcription initiation. b)Draw a diagram to illustrate the lac operon and explain how it functions in the presence of, i) glucose and ii) lactose in the culture mediumarrow_forwardWhat is the phenotype of an E. coli strain with a mutation in the lac operator that allows the lac repressor to irreversibly bind the operator? Assume glucose is absent. 1S A) O Transcription of the operon is very high whether lactose is present or not. B) O Transcription of the operon is very low whether lactose is present or not. C) O Transcription of the operon is high in the presence of lactose, and low in its absence. D) O Transcription of the operon is low in the presence of lactose, and high in its absence.arrow_forward
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