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14 Cards in this Set
- Front
- Back
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temperate phages can choose between a _____ or ______ existence
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- lystic
- lysogenic (equivalent of repression of the lytic phage, dormancy latency) |
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What is the gene regulation during the lambda phage lytic phase?
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- PL & PR use RNA polymerase (short transcripts have terminators)
- PL makes N protein which can (in sufficient amounts) bind to host RNA polymerase and cause it to not recognize PL & PR terminators - therefore N is an ANTITERMINATOR - Q made from non-termination of PR is an anti terminator for the Plate genes - once you go through Plate you are committed to lysis |
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The only gene not transcribed in the lytic cycle is _____, which is a repressor of lytic growth
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- cI (c1)
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What is the gene regulation during the lambda phage lysogenic cycle?
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- host RNA polymerase transcribes PL & PR
- N from PL causes RNA polymerase not to recognize termination sites (anti-terminator) - CII (C2) is now made from PR --> positive regulator of Pre promoter (promoter for repressor establishment) - when cII present in sufficient amounts can stimulate Pre promoter & Pint promoter (makes integrase) - Pre makes cI protein which dimerizes and shuts of PL & PR - it also binds Prm promoter (promoter for repressor maintenance) - positive regulator of itself - keeps making cI |
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Between what genes does lambda phage integrate? What is the orientation of J & integrase? What is the order of genes)
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- galactose & biotin
- galactose near integrase - J near biotin - order is galactose - attB - integrase --> J - attP - biotin |
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During lysogeny, there is _____ that is binding to Pint making integrase & _____ repressing PL & PR, also binding Prm to make more of itself
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- cII
- cI |
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What kind of mediums stimulate lysogeny vs. lytic phase?
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- lysogeny in poor carbon source environment b/c there is low cII protease
- lytic in rich medium with glucose & amino acids because there is high cII protease |
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N protein (anti-terminator) leads to transcription of ____ & ____ from the PR promoter. What determines lysis vs lysogeny?
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- Q
- cII - whether a bacterial protease cleaves up cII will determine lysis vs. lysogeny - if cII is chewed up/inactivated --> Q will accumulate = lysis --> under rich growth medium there is HIGH PROTEASE - if cII not chewed up then cI will be expressed & lysogeny will occur --> under poor growth medium there is LOW PROTEASE |
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______ is the process by which lambda gets out of the chromosome. It can only get out after what?
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- induction
- by SOS response elicited by DNA damage - this is an escape mechanism for damaged cell |
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Explain SOS response under normal bacteria conditions
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- physiologically: SOS (DNA repair) genes not expressed b/c repressed by LexA protein
- after DNA damage - RecA is activated --> touches LexA & induces autoproteolysis - LexA repressors autolyse & there is expression of SOS genes for DNA repair |
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How has lysogeny state adapted to work with SOS response in bacteria?
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- cI has designed itself to look like lexA protein
- RecA will touch it like it touches LexA & it will autoproteolyse - results in prophage excision & initiation of lytic program (if in good cell conditions) |
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What happens after induction?
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- phage genes expressed
- excision from chromosome - lytic/lysogeny decision made depending on conditions of cell |
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What is needed to insert lambda into bacterial chromosome? excise it?
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- integrase needed for insertion
- Xis & Int needed for excision |
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What happens during imprecise excision? Who can do this?
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- specialized transduction due to imprecise excision
- take out part of bacterial chromsome into lambda - ONLY TEMPERATE PHAGES can do specialized transduction |
