Chap 14 - Viruses Flashcards
Name three virologists who contributed to the early understanding of viruses. Hint: they studied the Tobacco Mosaic Virus.
IBM: D. Ivonwsky, and B. Beijerinck, A. Mayer
What was on of the first viruses studied?
Tobacco Mosaic virus.
Viruses are considered nonliving and are composed of nucleic acid and ___.
Protein (protein coat aka capsid)
Walter Reed studied this disease which goes to the liver, causing jaundice. Hint:mosquito is vector.
Yellow Fever
Twort and d’Herelle studied viruses that infected bacteria. What are those viruses called?
bacteriophages
The Viral genome contains either ___ or ___, but not both.
DNA or RNA
Name for the protein coat made up of capsomeres?
Capsid
T or F - Viruses lack the machinery for generating energy and large molecules
True
Receptor binding proteins that help the virus attach to the host cell as well as facilitate entry (can also help with release of virus)
Spikes
_____ + ____ = virus
capsid + genome
The first human virus discovered was? HInt: mosquito vector
Yellow fever
The first plant virus was?
Tobacco mosaic virus
Bacteriophages are what?
A bacteriophage is a virus that infects and replicates within a bacterium
What are the three shapes of viruses
Helical. Icosahedral, and Complex
This shape is a 20 sided polygon
Icosahedral
This shape has both helical and icosahedral
Complex
Do viruses have tissue specificity?
Yes- Tissue Tropism
The host range refers to what; and is based on what?
Organisms that the virus can infect. Capsid, envelope or spike structure.
T or F - Viruses do not need a specific receptor in order to invade the host cell.
False - they do need specific receptors.
Name the committee who is developing a classification system for viruses
International Committee on Taxonomy of Viruses (ICTV)
How are viruses currently classified?
By their genomes (DNA vs RNA)
T or F - RNA Viruses can be either single or double stranded RNA genomes
True.
Where is virus RNA replicated?
At the host cell ribosomes (in cytoplasm)
Where is virus DNA replicated?
In the Host cell DNA (nucleus if euk)
What is a retrovirus and which is the most famous retrovirus?
HIV
Retroviruses are replicated indirectly through DNA intermediate using an use this enzyme called?
Reverse transcriptase enzyme. RTE
Viral Replication follows these steps:
Attachment - Penetration - Biosynthesis - Assembly (maturation) - Release (APBAR)
If the virus does not go to directly to the biosynthesis phase, what is this called?
Latency
This stage of replication “makes the parts” of the virus
biosynthesis
Replication of bacteriophages follows what two cycles?
Lytic (virulent) and Lysogenic (lazy)
Herpes is an example of the “lazy” phase of bacteriophage replication. What is the name for this phase?
lysogenic
Steps in Animal virus replication involve:
Attachment by receptors - Penetration (capsid and genome get in together!!!) - UNCOATING (Capsid off -releases genome) - Biosynthesis - Assembly - Release by budding
In Animal virus replication, where does the RNA replicate?
In the cytoplasm
Why are latent proviruses immune to the host body’s defenses?
because they are a part of the DNA. THe immune system looks for foreign protein, caps or spikes.
Antibodies are what?
Proteins made by immune system, they can clump up virus for removal.
When attempting to detect a viral infection, a light microscopes can be used to look for what?
CPE - cytopathic effects (damaged host cells)
In a primary cell culture, cells form a ______ in a culture dish?
Monolayer
In viewing a plate containing a monolayer of animal cells, what do you look for formation of in terms of virus detection?
formation of plaques (clear zones where the virus has killed the host cell)
The only vaccine that exists to combat cancer is for what virus?
HPV (Human Papilloma Virus)
(SKIPPED SLIDE) Protooncogenes can be transformed to oncogenes by:
Radiation - chemical carcinogens - DNA damage - viruses
The construction of the capsid’s amino acids protect viruses from _____, ______, and _______.
Temperature, pH, and other environmental fluctuations
The completely assembled and infectious virus outside its host cell is known as a:
A Virion
Archaeal viruses are morphologically unique because why?
They often have spindle shapes
Even within its host range (rang of organisms it can infect) there are limitations as to which TISSUE it can infect. This limitation is called?
tissue tropism
Can a negative RNA genome virus be directly transcribed into protein?
No. Only a positive single strand can be read by ribosome and converted immediately in to protein.
Negative Strands of RNA viruses must go through a step to be converted into proteins. What is the step?
First converted to (+), then can be made into protein (spikes, capsids, etc.)
What is the name for an RNA virus that can convert back into DNA?
Retroviruses (retro = go backward)
The viral DNA of a bacterial virus that is inserted into the bacterial DNA and is passed on from one generation to the next during binary fission.
Prophage
This is a malignant tumor that begins growing in connective tissue such as muscle bone, fat, or cartilage.
Sarcoma
These are tiny fragments of infectious RNA, that lack capsid and spikes, and cause diseases in crop plants.
Viroids (infectious RNA that lacks capsid and spikes)
One hypothesis about viroids suggests that they originated as what?
Introns
Infectious proteins (lack DNA and RNA)
Prions
Early virologist who coined the term virus
Beijernick
What are signs of Tobacco Mosaic Disease
Tobacco leaves shrivel and assume mosaic appearance
Which is smaller, bacteria or virus?
VIrus
How are viruses cultured?
Egg method developed by woodruff and goodpasture
Who developed a method to mass produce vaccine?
Salk
True or False: Viruses replicate by taking over the host cell
True
Does Nucleic Acid occur in single or double strand? Linear or circular?
Both. Both.
A virus without an envelope is referred to as a ___________ virus.
Naked
Flu Viruses are made of _NA. Herpes is made of _NA.
Flu = RNA/ Herpes = DNA
Where does the virus obtain materials such as lipids and proteins?
From host cell
Does shape determine where the virus will attach?
Yes
How does viral structure determine host range and tissue tropism?
HR: is based on virus’ capsid or envelope.
TT: Specific receptors are required. WIthout receptor and complementary protein, virus cannot infect.
How do antivirals work?
remove the receptor, virus cannot bind
In Viral replication, what takes place during biosynthesis ?
Nucleic acid is replicated. Viral proteins, including capsid and tail fiber/spike proteins are made.
What takes place during assembly?
Capsid proteins and nucleic acid are assembled into nucleocapsids.
What may happen as the virus is released during replication?
Possibly kill host as rips through membrane.
Damage the host
VIRUS MAY STEAL NUCLEOTIDES, ATP and ENZYMES!
What is the name for a virus that has been emptied of it’s DNA and is now worthless?
Ghostphage
How does a virus benefit from the lysogenic cycle (lazy cheetos)?
Once the prophage (dna->bacterial chromosome) is inserted, it is copied during fission. Also, immune system cannot detect.
Herpes is an example of a virus that leaves the ______ cycle for the _______ cycle.
Lysogenic; lytic
The lytic cycle includes the steps from penetration, through release (the active assembly and maturation of viruses) in an an animal cell? Many virions are produced.
This infection is considered?
productive
Produces virus, they are productive at maturing…
In animal cells, at the attachment site, the virus enter the cell through endocytosis or though fusion with membrane. What is the next step that happens in animal cells but not bacterial cells?
uncoating! Once inside the cell, the capsid disassembles from the genome, genome then heads for replication or transcription.
Where in an animal cell are “parts” made for the virus?
Cytoplasm. Parts are protein which is made by ribosomes in the cytoplasm.
Do proviruses hang out and wait or are they active?
Hang out and wait.
What is it called when a virus fuses with the plasma membrane and then releases the virion outside of the host cell?
budding
What is the difference between a retrovirus and a provirus?
A retrovirus is an infectious unit that exists outside of a cell and has a protein coat and a lipid membrane
A provirus is a integrated retrovirus in the host DNA.
Which virus encodes a repressor protein that prevents activation (hint: prevent activation = not active)?
provirus
What are two possible types of infections one may experience?
Productive or Latent
If a cell is not destroyed after the virus exits, will it be attacked again?
“Why the F not?” - Dr. Pepper
Yes!
How are most viral diseases diagnosed?
Symptoms (measles rash - herpes blister - etc)
Light microscopes (view syncytia)
electron microscopes (view cells)
Serology (looks for large amount of antibodies in the blood. If present (+) for virus)
How do antibodies, which are made by the immune system, remove virus?
Clumps to virus, macrophage destroys
A clone of abnormal cells…
tumor
Uncontrolled growth and spread of cells…
cancer
Difference between benign and malignant
Benign - non cancerous
Malignant - metastasizes
Name for viruses that cause cancer…
Oncogenic virus
How do viruses cause cancer?
Interrupt meitosis (causing uncontrolled cell division)
Activate oncogenes
What is it called when 2 or more viruses exchange info?
genetic recombination
Can genetic recombination expand the host range of a virus? New viruses?
Yes. Yes.
TSE: Transmissible (from one organism to another) spongeform (turns brain to a sponge) encephalopathies (inflammation of brain) is related to what infection?
Infection caused by prion
Stanley Prusiner discovered the proteinaceous infectious particle known as?
Prion (Prusiner…prius…prions)
How do prions damage brain cells?
abnormal prions change the shape of normal protein in the brain (normal prions).
