The size of a DNA fragment that can be inserted into an unmodified λ vector is very limited. Large segment in the central region of the λ DNA molecule can be removed without affecting the ability of the phage to infect Escherichia coli cells. However, the deletion of this non- essential region does affect the life cycle of the bacteriophage. Explain this statement.

The size of a DNA fragment that can be inserted into an unmodified λ vector is very limited. Large segment in the central region of the λ DNA molecule can be removed without affecting the ability of the phage to infect Escherichia coli cells. However, the deletion of this non- essential region does affect the life cycle of the bacteriophage. Explain this statement.

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter17: Bacterial And Viral Genetics

Section: Chapter Questions

Problem 1ITD

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The linear dsDNA genome of λ binds on the LamB receptor of E. Coli and conducts a normal lysogenic cycle. Exposure to stress will cause the excision of λ prophage from the E. Coli genome. The excised λ genome is then replicated, packaged, and released from the cell as mature λ phage particles and ready to infect other bacterial cells. Among λ phage particles,the transducing phage mediates a specific type of recombination. Understand this scenario and answer the following questions. 1. What are the basic requirements for the insertion of λ into the E. Coli genome? 2. What special features are found in the λ insertion site? 3. What type of recombination occurs with λ insertion in the E. Coli genome? 4. How you will differentiate λ transducing phage from normal λ phage? 5. What exclusive mechanism λ phage utilizes for recombination?
When various strains of λ phage are seeded on a lawn of E. coli, they can form clear or turbid plaques. (b) For mutant λ phages that can only form clear plaques, give two different types of mutation in the phage that can explain the clear plaque phenotype.
when various strains of lambda phage are seeded on a lawn of e.coli, they can form clear or turbid plaques. Explain the difference between the two types of plaques. can all bacteriophage form clear and turbid plaques?
A bacteriophage λ is found that is able to lysogenize itsE. coli host at 30°C but not at 42°C. What genes may bemutant in this phage?
When bacteriophage P1 causes E. coli to lyse, the resulting materialis called a P1 lysate. What type of genetic material would befound in most of the P1 phages in the lysate? What kind of geneticmaterial is occasionally found within a P1 phage?
The protein of T2 bacteriophage is labeled with 35S and the DNA with 32p. Where would one detect most of the 32p if the T2 bacteriophage were allowed to infect the bacteria? O on the phage coat surrounding the T2 bacteriophage on the membrane of the infected bacteria O inside the T2 bacteriophage capsid O inside the infected bacteria O The 32P would be equally distributed within the T2 bacteriophage and infected bacteria
In Hershey-Chase experiment, bacteriophages protein coats were tagged with radioactive isotope S-32. These phages were used to infect E. coli cells and the cells were further centrifuged to form pellets. Why was the radioactivity level of S-32 found greater outside the cells compared to the E. coli cell pellets? Explain briefly. If the experiment is repeated in the same manner but this time the phage protein coats are labelled with isotope X and the phage DNA with isotope Y, which isotope’s radioactivity will be found in greater amounts in the E. coli cell pellets after centrifugation? Explain briefly.
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An ade+ arg+ cys+ his+ leu+ pro+ bacterial strain is knownto be lysogenic for a newly discovered phage, but the siteof the prophage is not known. The bacterial map isleucysarghisadeproThe lysogenic strain is used as a source of the phage, andthe phages are added to a bacterial strain of genotypeade- arg- cys- his- leu- pro-. After a short incubation,samples of these bacteria are plated on six differentmedia, with the supplementations indicated in thefollowing table. The table also shows whether colonieswere observed on the various media.PresenceMedium Ade Arg Cys His Leu Pro of colonies1 - + + + + + N2 + - + + + + N3 + + - + + + C4 + + + - + + N5 + + + + - + C6 + + + + + - NNutrient supplementation in medium(In this table, a plus sign indicates the presence of anutrient supplement, a minus sign indicates that asupplement is not present, N indicates no colonies, and Cindicates colonies present.)a. What genetic process is at work here?b. What is the approximate locus of the prophage?
Describe the process of replication of a Lytic phage and a Lysogenic phage. In your answer you must include the different steps of the replication process as well as appropriate terms used to name these steps of the process. Compare and contrast both methods of replication and indicate the relevance of lysogenic cycle of phage replication to bacterial antibiotic resistance.
What would happen to the ability of bacteriophage λ tolyse a host cell if it acquired a mutation in the OR bindingsite for the Cro protein? Why?
One of the reasons why phage therapy has not been applied widely is that bacteria can become resistant to bacteriophages as well, through mutations in genes encoding for specific proteins. What would be a protein in the bacterial cell that, if mutated, would make that cell resistant to phage infection?