When f ( f= temperate phage (a.k.a. âFifiâ)) lac+ his+ lysogens areinduced, viable f phage that can transduce the lac+ genes are
recovered at a low but detectable frequency. However, f capable oftransducing his+ cannot be
recovered. Please help with an explanation.
When f ( f= temperate phage (a.k.a. âFifiâ)) lac+ his+ lysogens areinduced, viable f phage that can transduce the lac+ genes are
recovered at a low but detectable frequency. However, f capable oftransducing his+ cannot be
recovered. Please help with an explanation.
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For this question, focus on four parts:
I, the gene that produces the repressor protein;
P, the promoter region where RNA polymerase binds to initiate transcription;
O, the Operator site, where the repressor binds. When the repressor binds, it prevents transcription; and
ZYA, the three structural genes, all of which are required for the successful utilization of lactose as a food source.
In the left column of the table below, we indicate the genetic composition at the lac operon of particular strains of E. coli cells. A "+" (plus sign) following the letter indicates the wild-type allele (or normally functioning version of the gene). For I, P, and ZYA, a "-" (negative sign) following the letter indicates the mutant allele (or non-functional version of the gene). For the O allele, a "C" indicates the mutant or constitutive allele. It is not functional in that the repressor cannot bind, but it is functional in that transcription can still occur.
Given the conditions stated in each column, please indicate for each genotype whether lac mRNA is produced and at what level by typing in one of the following words in each cell in the table:
"Abundant"
"Minimal"
"None"
The completely wild-type genotype has already been filled in.
| Cellular conditions: | |||
| Genotype | Glucose present (low cAMP) and no lactose | Glucose present (low cAMP) and lactose present | No glucose (high cAMP) and lactose present |
| I+ P+ O+ ZYA+ | None | Minimal | Abundant |
| I- P+ O+ ZYA+ | |||
| I+ P- O+ ZYA+ | |||
| I+ P+ Oc ZYA+ | |||
| I+ P+ O+ ZYA- | |||
1. Select all of the true statements regarding phageconversion.
| -The incorporation of viral genesinto the host cell's DNA is an example of phage conversion. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| -The expression of the incorporatedgenes and the resulting alteration of the bacterial phenotype is anexample of phage conversion. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| -Cholera toxin genes have a viralorigin. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| -The cholera toxin is produced bythe virus. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| -The cholera toxin itself is transferred to Vibriocholerae by a virus. 2. Viruses grown in media with radioactive sulfur haveradioactive capsids. Why?
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