Homework Answers
The Lac operon will be expressed in each of the three E. coli strains as shown in the table below:
| Environment |
Normal E. coli cells (wild-type) |
E. coli that have LacI deleted | E. coli with the CAP binding site deleted |
|
High glucose, No lactose |
No expression | No expression | No expression |
| High glucose, High lactose | low expression | No expression | High expression |
| No glucose, No lactose | No expression | High expression | No expression |
| No glucose, High lactose | High expression | High expression | High expression |
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3. The CAP activator protein and the Lac repressor both control the Lac operon (see Figure...
1) The lac operon is… a) Positive repressible b) Both negative inducible and positive repressible c)...
1) The lac operon is… a) Positive repressible b) Both negative inducible and positive repressible c) Positive inducible d) Negative inducible 2) An activator regulatory protein… a) Is involved in negative regulatory control b) Is a cis acting regulatory element c) Recruits RNA polymerase to the promoter d) Prevents RNA polymerase from binding the promoter 3) For the lac operon, the presence of the substrate (lactose) activates the repressor. True or False? a) true b) false 4) cAMP… a) Activates...
26. The lac operon in E. coli consists of genes that code for enzymes necessary for...
26. The lac operon in E. coli consists of genes that code for enzymes necessary for the breakdown of lactose. When lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. When lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. In the absence of glucose (a preferred energy source for bacteria), the protein CAP binds to a regulatory...
Microbiology question 51. Lacl regulates the expression of the lac operon, which encodes enzymes necessary for...
Microbiology question
51. Lacl regulates the expression of the lac operon, which encodes enzymes necessary for lactose metabolism. The genotypes of different E. coli strains are listed below. (For this exercise, lacP refers to the promoter, and lacO refers to the operator site where Lacl binds. lacl+ means wild-type, whereas lacl- indicates a loss-of-function mutation. lacO- means that Lacl cannot bind the operator.) For each strain, indicate whether the LacZ protein will be synthesized under the conditions indicated, when glucose...
for 1-5 define those The Lac operon is an inducible set of genes found in bacteria...
for
1-5 define those
The Lac operon is an inducible set of genes found in bacteria cells that helps the bacteria to metabolize the disaccharide lactose. When it is turned on it produces proteins that pump lactose into the bacteria cell and break it down into glucose and galactose, which can then be used by the bacteria as a source of energy The two figures below show the Lac Operon along with the lacl gene (which regulates the Lac operon...
A number of mutations affect the expression of the lactose operon in E. coir. I^- a...
A number of mutations affect the expression of the lactose operon in E. coir. I^- a mutant lac repressor that cannot bind the lac operator I^s a mutant lac repressor that cannot bind lactose O^c a mutant lac operator that cannot bind repressor Lacl P^- a mutant lac promoter that cannot bind RNA polymerase Z^- a mutant lacZ lost beta-galactosidase activity Y^- a mutant permease that cannot transport lactose into the cell Consider the following strains each with the indicated...
Imagine you are carrying out research on the lac operon. You isolate six mutations in the...
Imagine you are carrying out research on the lac
operon. You isolate six mutations in the lac operon by
measuring the amount of beta-galactosidase made in mutant cell line
under three different conditions: no lactose/no glucose; lactose
only; and lactose/glucose. Your results are shown in the table.
Strain
No Lactose, No Glucose
Lactose
Lactose, Glucose
Wild-type
None
High
Low
Mutant 1
None
None
None
Mutant 2
None
None
None
Mutant 3
None
Low
Low
Mutant 4
None
Low
Low
Mutant...
Mention the components of bacterial transcriptional switches. The Lac operon is regulated by both activator CAP...
Mention the components of bacterial transcriptional switches. The Lac operon is regulated by both activator CAP and Lac repressor. A scientist introduces a mutation in the gene encoding the activator CAP, making this allosteric protein insensitive to glucose levels. What outcomes do you expect if you culture the mutated bacteria in a culture medium with glucose and lactose. Give your explanation based on the mechanism of the Lac operon.
The gene machine program shows you what happens when lactose is present in E. coli, and...
The gene machine program shows you what happens when lactose is present in E. coli, and how the lac operon is under negative control. However, the lac operon is also under positive control from a protein called CRP, eAMP Receptor Protein. The absence of the lac repressor is essential but not sufficient for effective transcription of the lac operon. RNA polymerase also depends on the presence of CRP. Like the lac repressor, which can bind to the DNA and lactose....
You have systematically mutagenized the lac operon in E. coli to produce a mutation that disrupts...
You have systematically mutagenized the lac operon in E. coli to produce a mutation that disrupts the function of each of the following elements: a. the promoter for LacI (P(I)) b. the LacI gene c. CRP binding site d. the promoter for the lac operon (P(lac)) e. the operator sequence f. a mutation in lacZ that disrupts the coding region but does not disrupt transcription g. a mutation in lacZ that blocks transcription For each of the above mutations, what...
Consider what you know about the lac operon, and predict whether the repressor and the activator...
Consider what you know about the lac operon, and predict whether the repressor and the activator is active (able to bind to DNA) or inactive (unable to bind to DNA), and the level of transcription in the following scenarios. Options for transcription levels include high, medium, leaky and off. a. When lactose is present but glucose is not, the repressor is and the activator is leading to levels of transcription. and the activator is b. When lactose and glucose are...
26. The lac operon in E. coli consists of genes that code for enzymes necessary for the breakdown of lactose. When lactose is absent, the operon is inactive because a repressor protein binds to a specific site in the lac operon. When lactose is present, lactose molecules bind to the repressor protein, causing the repressor protein to dissociate from the binding site. In the absence of glucose (a preferred energy source for bacteria), the protein CAP binds to a regulatory...
Microbiology question
51. Lacl regulates the expression of the lac operon, which encodes enzymes necessary for lactose metabolism. The genotypes of different E. coli strains are listed below. (For this exercise, lacP refers to the promoter, and lacO refers to the operator site where Lacl binds. lacl+ means wild-type, whereas lacl- indicates a loss-of-function mutation. lacO- means that Lacl cannot bind the operator.) For each strain, indicate whether the LacZ protein will be synthesized under the conditions indicated, when glucose...
for
1-5 define those
The Lac operon is an inducible set of genes found in bacteria cells that helps the bacteria to metabolize the disaccharide lactose. When it is turned on it produces proteins that pump lactose into the bacteria cell and break it down into glucose and galactose, which can then be used by the bacteria as a source of energy The two figures below show the Lac Operon along with the lacl gene (which regulates the Lac operon...
A number of mutations affect the expression of the lactose operon in E. coir. I^- a mutant lac repressor that cannot bind the lac operator I^s a mutant lac repressor that cannot bind lactose O^c a mutant lac operator that cannot bind repressor Lacl P^- a mutant lac promoter that cannot bind RNA polymerase Z^- a mutant lacZ lost beta-galactosidase activity Y^- a mutant permease that cannot transport lactose into the cell Consider the following strains each with the indicated...
Imagine you are carrying out research on the lac
operon. You isolate six mutations in the lac operon by
measuring the amount of beta-galactosidase made in mutant cell line
under three different conditions: no lactose/no glucose; lactose
only; and lactose/glucose. Your results are shown in the table.
Strain
No Lactose, No Glucose
Lactose
Lactose, Glucose
Wild-type
None
High
Low
Mutant 1
None
None
None
Mutant 2
None
None
None
Mutant 3
None
Low
Low
Mutant 4
None
Low
Low
Mutant...
The gene machine program shows you what happens when lactose is present in E. coli, and how the lac operon is under negative control. However, the lac operon is also under positive control from a protein called CRP, eAMP Receptor Protein. The absence of the lac repressor is essential but not sufficient for effective transcription of the lac operon. RNA polymerase also depends on the presence of CRP. Like the lac repressor, which can bind to the DNA and lactose....
Consider what you know about the lac operon, and predict whether the repressor and the activator is active (able to bind to DNA) or inactive (unable to bind to DNA), and the level of transcription in the following scenarios. Options for transcription levels include high, medium, leaky and off. a. When lactose is present but glucose is not, the repressor is and the activator is leading to levels of transcription. and the activator is b. When lactose and glucose are...
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