Viruses, Prions, Viroids Flashcards by Comptone013 Unknown

What are characteristics of viruses?

-minuscule, acellular infectious agents
-have either DNA or RNA
-causes many infections of humans, animals, plants and bacteria (all living organisms)
-causes most of the diseases that plague the industrialized world
-cannot carry out any metabolic pathway
-neither grow nor respond to the environment
-CANNOT reproduce independently
-recruit a cell’s metabolic pathways to increase their numbers
-no cytoplasmic membrane, cytosol, organelles (one exception)
-have extra cellular and intracellular state

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What is the extracellular state of viruses?

-called virion
-protein coat (capsid) sorrounding nucleic acid
-nucleic acid and capsid also called nucleocapsid
-some have phospholipid envelope (around capsid)
-outermost layer provides protection and recognition sites for host cells

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What is the intracellular state of a virus?

-capsid removed
-nucleic acid only/ all that is left
(Genome)

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What is a capsid?

*PROTEIN COAT
-provide protection for viral nucleic acid
-means of attachment to host’s cells
-composed of proteinaceous subunits called “CAPSOMERES”

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Are capsomeres made of single or multiple types of proteins?

Multiple types of proteins

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What makes up capsids?

Capsomeres together make up capsids

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Can viruses be DNA, RNA, or both?

Viruses can be either DNA or RNA but never both.

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What types of DNA or RNA can viruses be?

-dsDNA (double stranded DNA)
-ssDNA (single stranded DNA)
-dsRNA (double stranded RNA)
-ssRNA (single stranded RNA)

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Viruses can usually appear__________________ or ___________________

-linear and segmented
-single and circular

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Most viruses are host ____________.

-specific

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Give example of host specific viruses.

-virus that infects liver only affects liver cells

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What is generalists?

Infect many kinds of cells in many different hosts

(Usually stick to same types of cells)

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Can viruses mutate and infect other host?

Ex. Horse——->Human

Y/N

YES

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What 3 basic shapes are viruses?

-Helical (Ebola)
-polyhedral (20 sides)
-complex (nucleocapsids w/ other membranes & proteins involved)

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What type of microscope can you see viruses in?

Light microscope

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Viruses are usually ___________

Geometric

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What creates the virus shape?

Capsid

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What is the viral envelope composed of ?

-phospholipid bilayer
-proteins

*some proteins virally coded glycoproteins (spikes)

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Envelope’s proteins and glycoproteins often play role in_________________.

Host recognition

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When a virus has a “corona” or “crown” what does this mean ?

It is covered in spikes

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The parts of a bacteriophage virus? (Virion)

-base
-tail
-sheath
-DNA
-capsid
-head
-tail fibers (legs)

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What are they 2 types of viral replication processes called? (Bacteria)

-Lytic replication
-lysogenic replication (lysogeny)

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What is lytic replication ?

-replication cycle usually results in death and lysis of host cell.

(Related to lysis; bursts out of cell)

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Stages of the lytic cycle?

-attachment
-entry
-synthesis
-assembly
-release

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What is lysogeny (lysogenic replication)

-lytic cycle is delayed, virus infects bacterial dna, which then replicates on its own until some external factor activates the lytic cycle. -modified replication cycle -infected host cells grow and reproduce normally -temperate phages—-prophages-inactive phages -lysogenic conversion results when phages carry genes that alter phenotype of a bacterium (transduction)

Replication of animal viruses have __________ ____________ replication pathways as bacteriophages.

Same basic

Differences result from: (ANIMAL VIRUSES replication vs. bacteria)

-presence of ENVELOPE around some viruses -eukaryotic nature of animal cells -LACK of cell wall in animal cells

In replication of animal viruses how does the virus find the host cell? (Attachment of animal virus)

Chemical attraction

Do animal viruses have tails? Do animal viruses have tail fibers?

-NO -NO

What are viruses without envelopes called?

-Naked Viruses

What are the 3 mechanisms of viral entry for animal viruses?

-Direct penetration -Membrane Fusion -Endocytosis

Explain Direct penetration of a virus

-virus without an envelope’s (naked virus) capsid attaches to receptors on cytoplasmic membrane and viral genome leaves capsid and penetrates host cell directly (only the genome, no capsid)

Explain membrane fusion of a virus .

ENVELOPED VIRUS attaches to receptors on cytoplasmic membrane of the host and envelope fuses with cytoplasmic membrane leaving behind viral glycoproteins , both capsid and genome enter the host cell and capsid begins “uncoating” inside the cytoplasm exposing the viral genome .

Explain endocytosis of a virus

Happens when EITHER enveloped or naked virus lands on plasma/cytoplasmic membrane and the membrane of the host ENGULFS the virus, which proceeds into the cytoplasm where it breaks down to reveal viral genome. *absorbed by phagocytosis

In synthesis of animal viruses, It requires various strategies depending on its?

Nucleic acid

In replication of animal viruses, Where do DNA viruses enter?

The nucleus

In replication of animal viruses, Where do RNA viruses replicate?

Cytoplasm

How is mRNA synthesized? (Animal replication)

RNA polymerase

DNA-containing viruses replicate their DNA in? (Animal replication)

Nucleus of host cell (By using viral enzymes)

Where is the capsid and other proteins synthesized for DNA-contains viruses (Animal replication)

In the cytoplasm (Using host cell enzymes)

What serves as a template for nucleic acid replication ?

-Viral RNA (Viral mRNA?)-Have to ask prof if its the same thing ?

In a retrovirus, how is DNA transcribed from the +RNA?

-uses enzyme Reverse Transcriptase

What is a common example of a retrovirus?

HIV

Where do most DNA viruses assemble? (Animal virus)

In the nucleus.

Where do most RNA viruses develop? (Animal viruses)

Cytoplasm

Number of viruses produced depends on type of virus and size and _________ ___ ________ ______

-health of host/ cell

Enveloped viruses cause persistent infections. Explain and give example.

-virus hangs around the cytoplasm _ex. HERPES

Naked viruses are released by ?

Exocytosis

What is latency? (Replication of animal viruses)

When animal viruses remain DORMANT/INACTIVE in host cells

How long can a virus be prolonged or latent?

Any length of time: days, weeks, months, years

Some latent viruses ____________ become incorporated into host chromosome

Do not

Incorporation of _____________ into host DNA is __________

-Viral genome -permanent

Any DNA that inserts into animal genome is permanent. T/F?

TRUE

Can viruses cause cancer ?

Yes, can sometimes cause cancer.

Cells are programmed for cell division a __________ number of times.

Specific

What is neoplasia?

-uncontrolled cell division in multicellular animal -on/off switches not working properly

Mass of neoplasticism cells is called ?

Tumor

What is a benign tumor?

Tumor that is not going to do anything

What is a malignant tumor? What is metastasis?

-Tumor that can spread by metastasis (cancerous) -pieces of malignant tumor break away/land somewhere else in the body

What is the oncogene?

It is a tumor gene

What are some environmental factors that contribute to the activation of oncogenes?

-ultraviolet light -radiation -carcinogens -viruses (only some, not all)

Viruses cause what percentage of human cancers?

20-25%

Some viruses carry copies of _________ as part of their genomes.

Oncogenes

Some viruses _________oncogenes already present in host.

Promote

Some viruses ___________ interfere with tumor repression .

Interfere

Specific viruses are known to cause about ________% of human cancers

Can viruses be seen in a light microscope? Y/N?

What CAN you study about viruses in a light microscope?

You can study host cells that have been infected using a light microscope.

What are the 2 types of cell cultures? (Culturing viruses in cell (tissue) culture)

-Diploid cell cultures -continuous cell cultures

Explain culturing viruses in cell (tissue) culture

Consists of cells isolated from an organism and grown on a medium or in a broth

Are viruses alive?

(Not by definition) -some consider them complex pathogenic chemical -others consider them the least complex living entities

Why do some believe that viruses are least complex living entities ?

-use sophisticated methods to invade cells -have the ability to take control of their host cell -are able to replicate themselves

Define coronaviruses

-large family of viruses causing upper respiratory infections

Explain the following : SARS-CoV MERS-CoV SARS-CoV-2

-Severe Acute Respiratory Syndrome (NOV 2002) -Middle East Respiratory Syndrome (2012) -Severe Acute Respiratory Syndrome causing Corona virus [COVID-19] (2019)

Characteristics of Viroids

-Extremely small, circular pieces of RNA -Similar to RNA viruses, but LACK CAPSID -may appear linear due to H bonding

Explain the structure of a viroid

-circular single-stranded RNA with some pairing between complementary bases and loops where no such pairing occurs.

What are other parasitic particles ?

-viroids -prions

Characteristics of prions?

-proteinaceous infectious agents -Cellular PrP protein -Prion PrP -Normally, nearby proteins and polysaccharides for PrP into cellular shape -PrP mutations result in formation of prion PrP

Explain cellular PrP protein

-in glial cell membranes of the brain -made by all mammals -normal structure with a-helices called cellular PrP

Explain Prion PrPed

Disease-causing form with B-pleated sheets called prion PrP

Explain prion diseases

-fatal neurological degeneration, fibril deposits in brain, and loss of brain matter. -large vacuoles from in brain -spongiform encephalopathies (looks like sponge, encephalo=in brain, Pathies=disease

How are prions destroyed ?

Only destroyed by incineration or autoclaving in 1N NaOH -under pressure

Vacuoles form from prions make it look ?

Makes tissue look spongy