1. A strain of E. coli is genetically engineered in which the lacZ and lacY removed and replaced with a gene encoding a fluorescent protein. In addition, scientist produced a partial diploid E. coli strain, i.e. bacteria that have one full copy of the lac operon in their chromosome plus another copy of the lac operon in a plasmid. The modified bacteria have the follow genetic components: genes are One copy of the operon in which the protein product fluoresces green is inserted into the bacteria chromosome One copy of the operon in which the protein product fluoresces red is inserted into a plasmid. Both copies of the lac operon carry one copy of wild-type Promoter (lacP) and Operator (lacO) cis-acting DNA sequences. The modified bacteria have only one copy of the lacI repressor gene in their chromosomes. The lac operon in the plasmid doesn't have the lacI gene. If both fluorescent proteins are expressed, the cells fluoresce yellow and if neither of the fluorescent proteins is expressed, the cells show no fluorescence. a. How would the cells fluoresce in the presence of the inducer, i.e. lactose? In the absence of lactose? Why? b. If the lacI gene, in the genetically engineered fluorescent strain were nonmutant (i.e. wild-type) but the lacO sequence on the chromosome is mutated to lacO, how would the cells fluoresce in the presence of lactose? In the absence of lactose? Why?

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Chapter17: Bacterial And Viral Genetics
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1. A strain of E. coli is genetically engineered in which the lacZ and lacY
removed and replaced with a gene encoding a fluorescent protein. In addition, scientist
produced a partial diploid E. coli strain, i.e. bacteria that have one full copy of the lac
operon in their chromosome plus another copy of the lac operon in a plasmid. The
modified bacteria have the follow genetic components:
genes are
One copy of the operon in which the protein product fluoresces green is inserted
into the bacteria chromosome
One copy of the operon in which the protein product fluoresces red is inserted
into a plasmid.
Both copies of the lac operon carry one copy of wild-type Promoter (lacP) and
Operator (lacO) cis-acting DNA sequences.
The modified bacteria have only one copy of the lacI repressor gene in their
chromosomes. The lac operon in the plasmid doesn't have the lacI gene.
If both fluorescent proteins are expressed, the cells fluoresce yellow and if neither of the
fluorescent proteins is expressed, the cells show no fluorescence.
a. How would the cells fluoresce in the presence of the inducer, i.e. lactose? In the
absence of lactose? Why?
b. If the lacI gene, in the genetically engineered fluorescent strain were nonmutant
(i.e. wild-type) but the lacO sequence on the chromosome is mutated to lacO,
how would the cells fluoresce in the presence of lactose? In the absence of
lactose? Why?
Transcribed Image Text:1. A strain of E. coli is genetically engineered in which the lacZ and lacY removed and replaced with a gene encoding a fluorescent protein. In addition, scientist produced a partial diploid E. coli strain, i.e. bacteria that have one full copy of the lac operon in their chromosome plus another copy of the lac operon in a plasmid. The modified bacteria have the follow genetic components: genes are One copy of the operon in which the protein product fluoresces green is inserted into the bacteria chromosome One copy of the operon in which the protein product fluoresces red is inserted into a plasmid. Both copies of the lac operon carry one copy of wild-type Promoter (lacP) and Operator (lacO) cis-acting DNA sequences. The modified bacteria have only one copy of the lacI repressor gene in their chromosomes. The lac operon in the plasmid doesn't have the lacI gene. If both fluorescent proteins are expressed, the cells fluoresce yellow and if neither of the fluorescent proteins is expressed, the cells show no fluorescence. a. How would the cells fluoresce in the presence of the inducer, i.e. lactose? In the absence of lactose? Why? b. If the lacI gene, in the genetically engineered fluorescent strain were nonmutant (i.e. wild-type) but the lacO sequence on the chromosome is mutated to lacO, how would the cells fluoresce in the presence of lactose? In the absence of lactose? Why?
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