Test 3 (viruses) Flashcards
Viruses components
Bacteriophages
viruses that kill bacteria
difficult to grow since they duplicate inside cells.
virion
-one complete virus
-they have more elaborate structure
Enveloped virus
- On surface add an extra layer for microbicides to target
-harder for immune system since they look like the host due to the host’s cell membrane.
plaques on lawn of bacteria
bacteriophage that killed the bacteria
Animal viruses
are grown in eggs, influenza vaccine are grown in chicken eggs or cell lines.
Lytic (lysis- to burst) cycle (bacteriophage replication)
-Attachment, bacteriophage attach to bacteria cell wall
-Penetration, DNA injected into bacteria
-DNA replication (using host’s enzymes)
-Transcription and translation, makes capsid
-Assembly, Makes new virus
-Release, bacteria cells bursts.
Lytic cycle process time and viruses per cell
20-40 minutes
50-200 viruses.
Lysogenic Cycle
- attaches and penetrates
-viral DNA incorporates to bacteria chromosome (prophage)
-as bacteria divides, viral DNA is copied too
-the prophage can stage inactive for many generations.
What triggers the prophage to leave the bacterial chromosome and start the lytic cycle ?
Random. UV light, chemicals, starvation.
CRISPR-Cas
Immune system for bacteria against phages.
-CRISPR gene gets transcribed RNA and binds to DNA of phage (become immune)
-Cas gene transcribed and translated producing Cas protein-DNAse (break down DNA that CRISPR RNA is bound to.
Animal viruses attachment
Animal cells don’t have walls, so animal viruses attach to cell membrane proteins.
-gives species specify and portal entry specificity (eg.. a virus that enters through respiratory tract may no be able to enter through urogenital)
Animal viruses penetration
ENDOCYTOSIS
-the whole virus enters cell
-virus ends up in a vesicle called phagosome (enveloped or not enveloped virus)
FUSION
-envelope virus fused into cell since they have host cell membrane
Animal virus uncoating
-uncoating is freeing nucleic acid from capsid.
-endocytosis virus, phagosome fuses with lysozome, and the enzymes uncoat the virus
-some bring own uncoating enzymes
-in bacteriophages no uncoating is necessary since DNA is injected.
Nucleic acid replication (animal viruses) in DNA viruses
Viral DNA enters host cell nucleus.
- DNA replicates (usually host or viral DNA polymerase) multiple copies of viral DNA.
-Transcription (using hosts RNA polymerase)
-Messenger RNA gets translated using hosts ribosome and tRNA.
-Capsid proteins, viral enzymes, and other proteins are made.
How can DNA viruses lead to cancer
when viral DNA is inserted into host DNA can interrupt genes controlling growth .
What is latency in DNA virus?
viral DNA inserted but not transcribed and translated (Ex chicken pox)
Positive strand RNA viruses (ready for translation, acts as mRNA)
-positive strand RNA enters host cell acts as mRNA
-translated using hosts ribosomes and tRNA which produces capsids, enzymes, and also RNA DEPENDENT RNA POLYMERASE.
-RNA DEPENDENT RNA POLYMERASE makes a complimentary RNA strand called negative strand RNA
-RNA DEPENDENT RNA POLYMERASE then read and makes complimentary positive RNA strands
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ANIMAL VIRUS ,,,,,,,, Negative strand RNA viruses (not ready to be translated)
-enter hosts with RNA dependent RNA polymerase (already in virion)
-RNA dependent RNA polymerase copies negative strand into positive strand
-positive strand gets copied and translated to CAPSIDS and RNA dependent RNA polymerase
-RNA dependent RNA polymerase copies positive strand RNA to more negative strand RNA
RNA Retroviruses (Animal viruses)
- RNA used to make DNA
-the enzyme REVERSE TRANSCRIPTASE converts RNA into DNA
-DNA is then incorporated into host DNA
——–possibility for latency and disruption of hosts genes (cancer)
-DNA transcribed (RNA polymerase, host or viral) producing viral RNA
-Translated (with host ribosome and tRNA) making capsids and REVERSE TRASNCRIPTASE.
Negative and positive strand RNA do not cause latency or cancer why?
They never become DNA so not incorporated into our DNA.
Human genome project revealed about endogenous retroviruses?
-lots of them in us
- they incorporate into DNA then become egss+sperm which get passed on to future generations.
Assembly (Animal viruses)
Whatever they came in with will be packaged out with capsids and enzymes.
Release (Animal viruses)
LYSIS - cell burst (non-enveloped viruses)
Budding - take piece of cell membrane with them, does not burst the cell. (enveloped viruses)
Gene therapy?
inserting a good gene copy into cells that have bad ones.
Why are viruses used in gene therapy? and what type?
viruses get DNA into cells. modify virus to carry gene of interest.
-DNA viruses and retroviruses
Prions?
-infectious proteins.
-normal brain proteins occasionally (spontaneous) change in folding (not infectious) (mutations make more common)
-(infectious) contact with misfolded proteins due to contaminated instruments in brain surgery
-eating infected tissue
——prion diseases
-Kuru (due to canabolism)
-mad cow - (due feeding with ground up meat product
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