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15 Cards in this Set
- Front
- Back
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What are the 6 (SIX) steps of a phage life cycle?
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Attachment
Injection of DNA (or other nucleic acid) Transcription and Translation of viral genome Reproduction of genome / Synthesis of new particles Packaging Lysis |
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What is one way to detect the presence of phages?
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Plaques -- a small circular zone of no visible bacteria within the lawn of growth
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Name/describe the period in the life cycle of phage infection.
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Eclipse period -- no detectable infectious particle in or out of cell
Intracellular growth -- infectious particles can be found inside but not outside cell Latent period -- time while no phage particle are outside cell |
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Are tail fiber binding and baseplate binding reversible (weak) or not reversible, respectively?
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Tail fiber binding -- reversible
Baseplate binding -- irreversible |
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What is a temperate phage?
Name an example. |
Following infection, the phage might not necessarily begin production of phage particles and host cell lysis
--Lambda |
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Describe the lytic life cycle of Lambda.
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Binding of particle and DNA entry
Linear genome has ss overhangs (cos sites) at each end The ss overhangs are complementary to each other -- become circular with ss nicks Host DNA ligase seals nicks Bidirectional "theta" replication makes copies of lambda genome Circular genome undergoes rolling circle replication -- ss concatamer Second strand replication Concatamers cleaved at cos sites |
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What enzyme facilitates binding of the att phage region to the att region in the host genome?
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Integrase
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What competes with the Lambda repressor for binding to OL and OR?
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The cro gene
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What are OL and OR?
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OL and OR are operator/promoter sites found in the Lambda genome
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What compound does the Lambda repressor repress and cro activate?
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txn
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If the Lambda repressor wins the competition for binding to OL and OR, what process occurs?
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Lysogeny
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If the cro wins the competition for binding to OL and OR, what process occurs?
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Lysis
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How is the repressor also responsible for interference in Lambda?
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A cell with a prophage will make lambda repressor protein. This will bind the DNA of any incoming phage and prevent its transcription
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In reference to Lambda, what is induction?
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A switch from lysogeny to lysis.
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What cause induction in Lambda? How?
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DNA damage (i.e. UV radiation) -- UV radiation activates the protease activity of RecA, and RecA will proteolyze lambda repressor.
This allows production of cro, which leads to the lytic cycle, including excision of the prophage from the genome (prophage leaves the bacterial genome as a circle) |
