LEC EXAM #1 CHP. 6 Flashcards
Is a virus a living organism?
No, viruses are considered acellular and needs a host cell/genome to survive
What is the general structure of a virus?
- Extremely small
- Bacteriophage structure
- Capsid protein coat that protects viral genome
- Has spikes that binds to host cell receptor
Enveloped virus:
-Contains genetic material, capsid and lipid bilayer surrounding capsid
Naked/non-enveloped virus:
- No surrounding bilayer
- Contains only genetic material and capsid
Outer shell of a virus is made of?
Capsomeres that make up capsid
How are viruses grown in the laboratory?
Viruses can be grown in a host (in vivo) or in a petri dish, or flask (in vitro).
How are animal viruses identified in the lab?
Virus is grown in vivo (inside the cell) and the cell is observed for cytopathic effects
Mycoplasma vs. viral particles
Mycoplasmas have the ability to replicate their own genome
Viral particles have to use host cell to replicate
Mycoplasmas contain:
Cholesterol in their cell membrane
Where do mycoplasma cells enter the body first?
Mucosal cell in genitals
Mycoplasma characteristics: (6)
- No cell wall
- Smallest known living organism
- Pleomorphic
- Contains cholesterol + other sterols in cell membrane
- Can survive inside cells
- Found in soil, plants, and animals
Goal of capsid:
To protect genome in cell
Spikes help with:
Attachment to the host cell in BOTH enveloped and non-enveloped viruses
What do bacteriophages do?
Replicate genetic material and proteins
Spikes are made of:
Glycoproteins
Spikes on capsids are:
Sheath and tail fibers that attaches and inserts genomes into host cells
Capsid in both enveloped and non-enveloped can cause:
Immune response
How do bacteriophages replicate in prokaryotic host?
LYTIC CYCLE
Attachment to cell-> infects by penetration of genome-> host DNA destroyed-> new phage particles are made -> lyses and kills cell
Lytic and lysogenic cycle: (temperate phage)
Attachment to cell-> phage DNA integrates itself with host DNA-> cell replicates-> under stressful condition phage pops out of genome and produces its parts-> goes through lytic cycle-> lyses and kills cell
Viral infection of eukaryotic host cell: lytic cycle
- Entry is either by endocytosis for non-enveloped or membrane fusion for enveloped
- Attachment of virus
- Penetration of virus into membrane
- Uncoating of viral contents
- Biosynthesis: RNA enters nucleus and is replicated by RNA polymerase
- Assembly of new phage particles
- Release of viral particles into EXF but host cell does NOT die
Family ends in:
-virdidae
Genes end in:
-virus
What is the filter porte size for viral isolation from bacterial particles?
0.2 microns
Viral classification of +ssRNA and -ssRNA:
+ssRNA (sense strand)
-ssRNA (anti-sensens strand that is complimentary to sense strand)
Goal of temperate phage:
To incorporate DNA into host cells DNA
In latent infection:
Viral loads increased
In viral growth:
Viral loads deceased
HeLa cells by:
Henrietta Lax
Antibodies are specific for spikes on specific viruses.
T or F
True
What process happens in HIV?
HIV binds GP120 to CD4-> causes it to bind to coreceptor CCR5-> fusion of membranes + viral genetic material inserted into host cell-> dumps reverse transcriptase, integrase, and RNA into host cell-> viral DNA is formed from viral RNA via reverse transcription-> viral DNA combines with integrase to go into nucleus to make viral proteins (capsids and spikes) and viral proteins come out to get used or packaged-> buds off to infect other cells
Viruses enter eukaryotic host cell via:
Endocytosis for non-enveloped viruses or membrane fusion for enveloped viruses
How are viruses treated?
With antiviral drugs that interfere with some parts of their “life cycles”
What are some cytopathic effects of viruses on human/animal cells? (7)
- Loss of adherence to surface
- Changes in cell shape from flat to round
- Shrinkage of nucleus
- Vacuoles in cytoplasm
- Formation of cytoplasmic membrane and formation of mutlinucleated syncytial
- Inclusion bodies in the nucleus or cytoplasm
- Complete cell lysis
What is generalized transduction?
- Transfer and packaging of pure DNA into the virus
- Lytic cycle
What is specialized transduction?
- Transfer and packaging of small percentage of bacterial DNA with the viral DNA genome
- Lysogenic cycle
Steps of generalized transduction?
- Phage infects bacterial cell
- Phage DNA replicates and bacterial DNA is fragmented/hydrolyzed into small pieces
- During assembly, bacterial DNA fragment accidentally gets packaged into a phage head
- New phages lyse out and kill cell
- Phages infect other cells, some of these have bacterial genes that they donate to the new host cell= crossing over of genes
Steps of specialized transduction?
- Phage infects bacterial cell
- Integrates its DNA with bacterial DNA
- Host cell with phage DNA + bacterial DNA replicates into daughter cells
- Phage remains dormant until stressful condition arises
- Goes through lytic cycle*
- Phage destroys bacterial DNA and replicates its DNA but has some bacterial DNA parts in it
- Phage DNA is packaged with bacterial DNA
- Phages lyse out and kill cell
- Phages infect other cells with mixed DNA-> donates genes to a new host cell= crossing over of genes
Difference between packaging processes in generalized and specialized transduction?
In generalized transduction, bacterial DNA is packaged separately from phage DNA
In specialized transduction, bacterial DNA is MIXED with phage DNA
If you have a -ssRNA virus, what must it do to its genome before it can start making proteins/proteins?
Make its +ssRNA compliment
Double stranded RNA have:
BOTH + and -
Single stranded RNA have:
+ OR -
RdRP:
RNA polymerase that does transcription of any - strand and makes it into + strand to make proteins
+ssRNA is used:
By the host cell’s 80s ribosome to make viral proteins (spikes and capsids)
OR
Make more -ssRNA for new viral particles
What is responsible for converting RNA into DNA?
Reverse transcriptase
In acute infection:
Viral load increases immediately
In persistant infection:
Viral load increases consistently over time
Viral growth steps: (4)
- inoculation: inoculum of virus binds to cell
- eclipse: virions penetrate the cell
- burst: host cells release many viral particles
- burst size: number of visions released per bacterium
Antibodies are specific for the spikes on a specific virus:
T or F
TRUE
Direct assay:
Spikes cause hemagglutination of virus and RBC
Indirect assay:
No hemagglutination because antibodies bind to virus-> virus can’t bind to RBC
