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Viruses: 13
Viruses, Viroids & Prions
| Question | Answer |
|---|---|
| each virus particle | virion |
| virus characteristics | obligatory intracellular parasites contain DNA or RNA Some are enclosed by an envelope Don't have own metabolism, multiply by using synthesizing machinery of host host specific infection |
| virus sizes | various sizes, mostly smaller than bacteria |
| Structure of a Polyhedral Virus | Nucleic acid Helical or spiral capsid Envelope spikes |
| Nucleic acid: DNA or RNA viruses | may be linear, circular, double-stranded, or single-stranded |
| Helical or spiral capsid: protein coat | composed of many capsomeres |
| Envelope: double lipid layer | some viruses that infect animals |
| Morphology of a Helical Virus | based on a capsid structure, complex |
| Helical | long rod |
| polyhedral | many sided |
| Virus family names | end in -viridae |
| Virus genus names | end in -virus |
| virus species | group of viruses that share same genetic information & host |
| subspecies | designated a number |
| names based on | nucleic acid, morhphology, strategy of replication |
| Herpesviridae: Herpesvirus | human herpes virus HHV-1 HHV-2 HHV-3 |
| Retroviridae: Lentivirus | Human immunodeficiency virus HIV-1 HIV-2 |
| Methods for growing viruses | living animals, cell culture, chick embryo |
| plaque method | bacteriophages 1)prepare a spread plate of bacteria 2)add bacteriophages 3)as virus replicates bacteria in area are destroyed leaving a clear zone:plaque |
| single viruses cause a plaque | pfu: plaque forming unit |
| continuous cell lines | HeLa cells: active telomerase, may be maintained indefinitely |
| Animal & plant viruses | homogeneous cells grown in culture media, can be propagated like bacterial cultures |
| CPE: can be detected and counted similar to plaques | cytopathic effect |
| virus infects cells | Cells in monolayer deteriorate as virus multiplies, CPE |
| Virus ID | Serological tests, Nucleic acids, CPE |
| Serological tests | most commonly used, detect antibodies against viruses in a patient,Western Blot |
| Nucleic Acids | restriction fragment length polymorphisms(RFLPs) & PCR(Polymerase chain reactions) |
| Viral multiplication | lytic cycle or lysogenic cycle |
| lytic cycle | ends with death & lysis of cell, virulent phage: T-even bacteriophage |
| lysogenic cycle | host cell remains alive, phage conversion, specialized transduction, temperate phage |
| Lytic Cycle | attachment, penetration, biosynthesis, maturation, release |
| attachment | called adsorption, phage attaches by tail fibers to host cell |
| penteration | opens cell wall(phage lysozyme), tail sheath contracts to force tail core & DNA into cell |
| biosynthesis | production of phage DNA & proteins, viral proteins(anti-sigma factor, DNase) interfeere with transcription & degrade host DNA |
| matruation | tails & head(DNA & capsids) are separately assembled |
| release | phage lysozyme breaks cell wall, T-even bacteriophage: large virus, complex virus, non-enveloped, head & tail |
| burst time | time elapse from attachment to release, 20-40 min |
| burst size | number of synthesized particle released, 50-200 |
| one-step growth experiment | mix bacterial host & phage, brief incubation(attachment), dilute greatly(no new infection), over time collect sample, & enzyme rate viruses |
| lysogenic cycle | capable of incorporating their DNA into host cell's DNA through specific recombination, chromosome replicates prophage replicates, may proceed to the lytic cycle depending on host cell's condition |
Created by:
mandilucille
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