Ch. 13 - Viruses, Virioids, and Prions Flashcards
What is the size range for viruses?
(what unit of measurement do we use to measure them)
wide range of sizes, but are VERY small
use nanometer (nm) (compared to bact. micrometer)
How is viral structure unique?
- acellular = not cells; no cytoplasm/CM/organelles
- single type of nucleic acid is present = DNA or RNA
-> viruses start off as either DNA or RNA virus
What are the structural components of a typical virus?
Briefly draw these structures and label them
(Genetic) Core: contains genetic material; DNA/RNA; AKA Genome
Capsid: surrounds/protects core; composed of capsomere proteins
Envelope: surrounds capsid (optional)
Spikes: attach to envelope (optional)
Viruses DO NOT ____________.
reproduce
Instead, they MULTIPLY
Where do viruses multiply?
inside living host cells (REQUIRED)
Describe what is meant when viruses are referred to as “obligate intracellular parasites”
this means viruses must enter inside of a living host cell and will cause harm to the host
TRUE or FALSE: A plant virus will infect an animal cell
False, because viruses show host specificity
TRUE or FALSE: Viral Hepatitis will infect the brain.
False, because viruses also show tissue specificity.
Understand host specificity and tissue specificity of viruses
Include examples
Host specificity = virus will only attack a specific host (Bacterial virus; bacteriophage will attack bacterium)
Tissue specificity: virus will only infect specific tissue (Viral Hepatitis infects liver; Viral Encephalitis infects brain)
Name some ways in which viruses are transmitted
by food, water, air, insects, direct contact
What is meant by “phage”
virus
PRACTICE:
What is a bacteriophage?
What is the host cell for a bacteriophage?
What is phage DNA?
Whose DNA does it belong to?
bacterial virus
bacteria
viral DNA
virus
Name the different “shapes”/morphology of viruses
Briefly describe and know/draw the shape
helical viruses (cylindrical head)
polyhedral virses
complex viruses
TRUE or FALSE: A complex virus will be found in an animal host cell.
False, because complex viruses are bacterial viruses, meaning it will only attack bacteria (bc of host specificity)
Describe the taxonomy of viruses
Include any information/examples about them
Family - Highest Taxon
- ends in -viridae
- ex: Herpesviridae, Retroviridae, Coronaviridae
Genus
- ends in -virus
- enterovirus, influenzavirus
Viral Species - Lowest Taxon
- A group of viruses sharing similar genetic information and ecological niche (host)
-> HIV (humans) and SIV (apes)
- Viral subspecies/strains
-> HSV-1; HSV-2; Influenza H1:N1
Describe the growth of Bacteriophages in the labroratory
Include what it will grown on, what does it form?
Bacteriophages are bacterial viruses, so they will be grown on a bacterial lawn on a plate
Plaques will form, which are areas of dead/damaged bacterial cells and no bacterial growth is happening in these areas
-> corresponds to single virus
-> expressed as PFU
Describe how animal viruses are grown in lab
grown in living animals, embryonated eggs, or animal cultures
-> virally infected animal cell is detetected via its deterioration, called cytopathic effect (CPE)
What is CPE (cytopathic effect)?
visible damage done to animal host cell
is specific/unique to animal host cell
How are viruses identified?
Which is the most common method?
Cytopathic effects (CPE): for animal virus identification\
Serological tests: MOST COMMON METHOD; look for the virus or antibody against virus
Polymerase Chain Reaction (PCR): isolate some viral DNA to make many copies
What is required in order for a virus to multiple?
must invade living host cell
virus must take over hosts metabolic machinery (host DNA); will telll the host DNA to make viral parts and to assemble them
What two cycles can Bacteriophages multiply by?
Describe
Lytic Cycle: required; causes lysis and death of bacterial host cell
Lysogenic Cycle: optional; does NOT cause death -> host cell divides; phage DNA embedded into bacterial host cell’s DNA = hybrid DNA/prophage
What is a virion?
newly-formed, mature virus
this is what leaves the bacterial host cell
Briefly describe the two options Bacteriophages have to multiply
Option #1: Enter and complete Lytic cycle ONLY -> Bacterial host cell death
Option #2: Enter Lytic cycle only and then pause -> enter and complete Lysogenic cycle (bacterial host cell divides and host already infected) -> Re-enter and complete Lytic Cycle -> host cell death
What are the stages of the Lytic Cycle for Bacteriophages?
Briefly describe them
- Attachment = to bacterial host cell
- Penetration = of phage DNA into host cell
- Biosynthesis = making the viral parts
- Maturation = assembly of viral parts
- Release = of virions -> will leave host cell and destroy host
Describe ATTACHMENT of the LYTIC CYCLE
- bacterial virus uses its tail fibers to attach to the cell wall receptors of bacterial host cell
- viral lysozyme (enzyme) makes hole in bacterial cell wall (so that viral DNA can enter host cell; bacterial virus does NOT enter)
Describe PENETRATION of the LYTIC CYCLE
- viral sheath is contracted which will push the viral DNA into bacterial host cell
- viral DNA now present in bacterial host cell
Describe BIOSYNTHESIS of the LYTIC CYCLE
- viral DNA incorporates into bacterial host DNA and takes over bacterial host cell’s DNA
- Bacterial host forced/committed to make viral components (proteins) through transcription and translation
(hybrid DNA –transcription-> RNA –translation–> protein)
Describe MATURATION of the LYTIC CYCLE
- viral components get assembled into virions
- virions are newly-made, mature viruses capable of infecting other cells
Describe RELEASE of the LYTIC CYCLE
- bacterial host cell lyses/ruptures when new virions are released
- results in death of bacterial host cell
Define Lysogeny
phage DNA integrates and remains dormant (delay in biosynthesis) in a host cell; phage particle (protein) production is delayed
Define prophage
“hybrid” DNA; is when phage DNA gets incorporated into host cell (bacteria) DNA
How does Lysogeny happen?
Phase DNA get incorporated into host cell DNA -> forms Prophage (hybrid DNA)
When host cell replicates, it also replicated the prophage and DOES NOT lead to the production of phage particles in host cell (delayed biosythesis)
Name and understand the 3 consequences of lysogeny
Include examples when possible
Phage Conversion: non-pathogenic bacteria becomes pathogenic bacteria
Latent Viral Infections: virus “hides out” in tissue (usually NS); symptoms decrease (ex: Shingles, Herpes)
Transformation: viruses turn-on cancer-causing genes (ex: HPV -> cervival cancer)
At what point does the Lysogenic Cycle start after the Lytic Cycle begins in terms of Bacteriophages?
- Attachment
- Penetration
- 1/2 Biosynthesis (formation of prophage)
- LYSOGENIC CYCLE STARTS AND FINISHES
- 2/2 Biosynthesis (make protein particles)
- Maturation
- Release
TRUE or FALSE: The multiplication process for animal viruses can be/is involved with the Lytic Cycle and Lysongenic Cycle
True
What are the stages of multiplication (Lytic Cycle) for animal viruses?
- Attachment
- Entry: by RME (non-envelope) or fusion (envelope)
- Uncoating: viral/host enzyme get ride of capside to expose genetic core
- Biosynthesis
- Maturation
- Release: by budding (envelope) or rupture (non-envelope)
Compare presence of envelope between animal viruses and bacteriophage
bacteriophage: non-enveloped
animal virus: non-eveloped or enveloped
Name two ways in which a virus can enter an animal host cell
Fusion: for enveloped virus
Receptor Mediated Endocytosis (RME): for non-eveloped virus
After entry of capside into animal host cell, _________ _________ must be ________ to ________ the ________ ________
protein capsid
disintegrated
expose
viral DNA
When animal viruses DNA incorporates into the animal host cells DNA, it forms a ________________.
How is this different from bacteriophages?
provirus
When viral DNA is integrated into bacterial DNA, it forms a prophage
At what point does the Lysogenic Cycle start after the Lytic Cycle begins in terms of Animal Viruses?
- Attachment
- Entry
- Uncoating
- 1/2 Biosynthesis (formation of provirus)
- LYSOGENIC CYCLE STARTS AND FINISHES
- 2/2 Biosynthesis (making viral parts)
- Maturation
- Release
Compare the type of nucleic acid found in Bacteriophages vs. Animal Viruses
Bacteriophages = DNA
Animal Viruses = DNA or RNA
Animal viruses can exist either as DNA or RNA.
How does provirus formation differ between an animal virus containing DNA vs. an animal virus containing RNA?
DNA:
- animal virus DNA can incorporate into animal host cell’s DNA to form a provirus
RNA:
- animal virus RNA CANNOT incorporate into animal host cell’s DNA
- animal virus RNA must get converted into DNA by enzyme Reverse Transcriptase via Reverse Transcription -> can now incorporate into animal host cells DNA to form provirus
Name 2 ways in which animal virus is released from the animal host cell
Budding: enveloped animal virus (buds out of animal host cell using its CM)
Rupture: non-enveloped animal virus
Compare and Contrast:
Bacterial Viruses from Animal Viruses
Include similar or differences in: anatomy, cycle/stages, “hybrid” DNA names, DNA/RNA virus, enveloped/non-enveloped, how viral DNA enters host cell, and any other extra info/
Bacterial Virus:
- sheath
- tail fibers
- penetration stage
- prophage
- DNA virus only
- Non-enveloped viruses
- only genome (DNA) enters host cell; virus does not enter
Animal Virus:
- entry and uncoating stage
- provirus
- DNA or RNA viruses
- enveloped and non-enveloped
- entire virus enters host cell
- capable of reverse transcription
BOTH:
- capsid
- lytic and lysogenic cyel
- Attachment, Biosytnehsis, Maturation, Release stages
- “multiplication”
- obligate intracellular parasites
Name some families that are DNA viruses and RNA viruses.
Include examples
DNA viruses:
- Poxviridae
-> smallpox, cowpox - Herpesviridae
-> cold sores, genital herpes, chickenpox, shingles
RNA viruses
- Retroviridae
-> HIV/AIDS, COVID-19
Some cancers are caused by viruses called ________
oncoviruses
Describe oncoviruses
(how do they develop, and how do they cause cancer?)
- may develop after viral infection
- some oncovirses can turn on “oncogenes” found in normal cells -> uncontrolled cell division -> transform normal cells into cancerous cells
Explain how oncoviruses turn on oncogenes
oncoviruses DNA becomes integrated into the host cell’s DNA and induces tumor (turns on oncogenes and cancer develops)
Name the three “categories” of infections
Describe them and include examples.
Acute Viral Infections:
- rapid onset of symptoms and short duration of infection
- ex: influenza
Latent Viral Infections
- hidden, inactive, dormant infection (virus hides)
- ex: cold sores, genital herpes, shingles
Persistent/Chronic Viral Infections
- late onset of symptoms, long duration, subclinical/mild symptoms
- ex: HIV/AIDS
Define/Describe Viriods
- smallest infectious pathogens in the world
- infectious RNA molecules
- causes plant disease (ex: Potato disease)
Define/Describe Prions
- infectious protein particles (NO CURE)
- highly resistant = destroy via incineration
- cause transmissible neurological disease (ex: Spongiform Encephalitis)
List several examples of Spongiform Encephalitis
- Mad Cow Disease (Bovine Spongiform Encephalopathy); in cows
- Creutzfeldt-Jakob Disease (CJD); in humans
- Sheep Scrapie; in sheep
