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14 Cards in this Set
- Front
- Back
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a ______ (protein coat) surrounds the viral genome. Some viruses have a ______ or _____ as well.
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- capsid
- lipid coat or "envelope" |
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What hapens in the lytic growth cycle?
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- bacteriophage inserts genome --> replicate/transcribe --> at right time lysin breaks open cell wall --> progeny phage spilled out
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What are the 7 stages of bacteriophage infection (APGRSAL)
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1) adsorption
2) penetration (injection/endocytosis/membrane fusion) 3) gene expression 4) nucleic acid replication 5) synthesis of structural proteins 6) assembly of virions 7) lysis - release |
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What can phages adsorb to on bacterial cell surfaces (4 things - POCP)? On eukaryotic cell receptor (1 thing - S)?
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Prokaryotes:
1) O-antigen in gram (-) bacteria (aka endotoxin, LPS) 2) porins in gram (-) bacteria 3) pili (adhesins) - gram +/- 4) capsules (antiphagocytic) - gram +/- Eukaryotes: 1) sialic acid residues |
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Difference b/w RNA virus (round one vs. filamentous) in terms of attaching to pilus?
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- round RNA virus adsorbs to pilus and rolls down into the bacteria
- filamentous DNA virus attaches to pilus and waits for it to retract to inject genome |
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What are the components of a phage?
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- capsid (coat protein), DNA core, collar, contractile sheath
- base plate w/ spikes - tail fibers |
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What are the 6 steps of adsorption & penetration by injection (ACCPIT)?
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1) attachment of tail fibers to outer membrane of gram - or cell wall of gram +
2) contraction fo tail fibers to allow base plate to touch cell surface 3) contraction of contractile sheath 4) passage of needle through cell wall 5) injection of phage DNA into intermembrane space 6) transportation of phage DNA into cytoplasm |
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Another way that eukaryotes can get a virus (that prokaryotes cannot) is ______. Viruses can also infect via ______
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- endocytosis
- membrane fusion |
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Once the head & tail are assembled, the joining happens _______ without covalent modification from chaperones that were needed in beginning
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- spontaneously
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What are the two mechanisms of transcript termination?
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1) factor-independent: coded in DNA as region of dyad symmpretry - when transcribed RNA forms "stem loop" aka hairpin structure --> RNA polymerase senses this & transcription stops & RNA is released
2) factor-dependent: Rho factor binds directly to RNA poymerase & causes polymerase to stop & release when reaching factor-dependent terminator |
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is phage T7 early mRNA synthesis factor-dependent or independent termination?
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- both
- first 8 minutes |
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Phage T7: First 1-8 minutes only ________ transcribed, 8-12 mins _______ transcribed, 12 mins only ______ made
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- early mRNA
- early & late RNAs - late RNAs |
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Phage T7: early promoter is recognized by ______, gene product 1 does what? How does regulation occur after this?
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- host RNA polymerase
- gene product 1 (Gp1): RNA polymerase specifically for late RNA promoters - late gene product 2 (Gp2) binds to host RNA polymerase holoenzyme & inhibits transcription initiation |
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How can bacteria survive virus infection?
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- mutation phage receptor, then phage mutates to recognize receptor, etc.
- survivors make enzymes that degrade (restrict) viral DNA --> mutants can arise that have lost restriction sites, host mutates again, etc. |
