Final Flashcards
(64 cards)
Define a virus and give some general characteristics
- obligate intracellular parasites
- have a nucleic acid EITHER: RNA or DNA
- invaded in a protein capsid that surrounds the Na
- May contain am envelope around the capsid
Old taxonomic system
Based only on human symptoms
Some cause more than one disease
Didn’t work for viruses that don’t infect humans
New taxonomic system
Nucleic acid
How they replicate
Morphology
Major steps for lytic bacteriophage infection
- attachment
- penetration- injects just DNA or RNA (protein stays outside)
- biosynthesis
- Maturation: components assemble into virions
- release host cell dies!!
What is biosynthesis
Phase DNA directs synthesis of viral components using host stuff
Lysogenic pathway in bacteriophage
Steps are same as lytic except what happens with the DNA
- DNA sometime integrates with bacterial DNA
- bacteria can then replicate normally
- cell doesn’t die
-sometimes virus DNA separates from bacterial DNA and continues with tthe lytic cycle (than cell dies)
What is a prophage
Happens In the lysogenic pathway
- bacterial viruses when some virus DNA integrates into the bacterial DNA
Animal virus life cycles
- Lyric
- Latent- cannot code for proteins
- Persistent/slow-small amts of virus always found
Where do DNA and RNA replicate in animal viruses
DNA - in nucleus of host
RNA - in cytoplasm of host
How do animal viruses differ from bacteriophage replication
Attachment- •receptor on cell membrane
•av do not have tails
Penetration- •endocytosis
•fusion
Fusion
Envelope fuses with plasma membrane and releases capsid
Endocytosis
Plasma mem folds inward to form vesicle which virus is in loses the envelope
How do animal viruses release
Budding- enveloped
Lysis- non enveloped
Antivirus drugs that inter fear with DNA and RNA synthesis
- Acyclovir
- Ribavirin
- Zidovudine (Azt)
Acyclovir
Inter fears with DNA and RNA synthesis
- for herpes virus
- administered orally/topically/or injected
Ribavirin
Stops RNA synthesis
- rotavirus treatment
- administered as aerosol
Zidovudine (Azt)
Inter fears with DNA and RNA synthesis
- HIV treatment
- blocks synthesis by reverse transcription
- fairly toxic
Enzyme inhibitors
- Nevirapine
2. Indinavir and saquinavir
Nevirapine
Enzyme inhibitor
- HIV treatment
- Inactivates reverse transcriptase
Indinavir and saquinavir
Enzyme inhibitor
- HIV treatment
- Protease inhibitor
Interferon
A natural product of the immune system which cells can produce antiviral proteins
- hepatitis treatment
Prions
proteinaceous infectious particle
-causes rare degenerative disorders
• diseases with long incubation periods
• always progressive and fatal
Mode of prion in the body
Folds abnormally from normal cellular form
Causes large vacuoles in the brain (spongiform encephalopathy)
Transmission of prions
- Eating cns from infected animal
- Transplanting nerve tissue
- Contaminated surgical instruments