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Microbio L6
| Question | Answer |
|---|---|
| Viruses: | Small infectious particle Non living, acellular, not metabolism Obligate intracellular parasite! |
| Virion | a virus particle |
| Viruses are not made of | cells |
| Capsid: | protein shell, protects the genome Individual capsid proteins called capsomeres |
| Helical: | spiral around the genome |
| Icosahedral: | shell around the genome (20 sided die) |
| Complex: | non-symmetrical or complicated shapes |
| Enveloped viruses: | have a lipid membrane Take from host cell, another layer of protection |
| Naked viruses: | lack a lipid envelope Usually burst host cell |
| Spike proteins: | large proteins that extend from the envelope (or from the capsid in naked viruses) The key that lets the virus into the cell |
| Tropism | what cell type/species a virus can infect |
| 2 spike proteins on influenza virus: | Hemagglutinin- used for attachment Neuraminidase: used for exit |
| Viral genomes | Could be DNA or RNA Could be single-stranded or double-stranded Could be linear, circular, or segmented |
| DNA viruses: | usually steal host polymerases, still follow the central dogma |
| RNA viruses: | break central dogma Make RNA from an RNA template Needs a new special polymerase |
| RNA -> RNA | RdRp |
| Retroviruses: | throw the central dogma out the window From RNA template, makes DNA (transcription in reverse) Then turn DNA back into RNA |
| RNA->DNA->RNA | RT |
| Viral genomes change | very rapidly!!! Compared to eukaryotic (or even prokaryotic) genomes |
| Random mutations: | occur due to errors in replication RdRp and RT have terrible proofreading |
| Reassortment: | when segmented viruses co-infect, they can swap genome segments |
| Drift: | gradual accumulation of many small changes - random mutations - predictable with the flu |
| Shift: | sudden big change in genome - reassortment - you cannot predict! |
| Bacteriophage (phage): | virus that infects bacteria 5 main stages of replication |
| Lytic | Replicate, then burst of out the cell, killing the cell |
| Lysogeny: | phage goes “quiet,” inserts its genome into the host genome Integration Prophage: integrated viral genome Can switch back to lysis when host is stressed Abandon ship |
| Animal virus replication 6 steps | Attachment Penetration Uncoating Replication Assembly Release **All steps could be inhibited by some antiviral |
| Attachment | Controlled by spike proteins Tropism of both what species is infected, and what tissue/cell type |
| Entry | Fusion and Endocytosis |
| Fusion: | envelope fuses with host membrane, dumping capsid inside |
| Endocytosis | whole virus is taken in a vesicle, eventually has to escape into cytoplasm |
| Release | Budding and Naked viruses usually just lyse the hose |
| Budding: | virus pushes out through host membrane, getting its own membrane DOES NOT KILL THE CELL |
| Infection types | Acute and Persistent |
| Acute: | short term infection, then cleared |
| Persistent: | asts for a long time (never fully cleared) Chronic and Latent |
| Chronic | slow replication |
| Latent: | no replication, then suddenly a short burst viruses that flare up, like chicken pox...stays in your body forever :( |
| Oncoviruses | Some persistent viruses can cause cancer During their “hiding” the viral proteins can dysregulate cell division |
Created by:
liladdoyle