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61 Cards in this Set
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- Back
Describe what happened when the Spaniards conquered America |
600 Spaniards conquered 8 million native Americans. They brought with them small pox and the native americans had no immunity to the virus. They did not have the right genes to fight small pox. They got conjunctivitis and died from it. The pink eye became meningitis.
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What happened during the Spanish flu virus? |
from 1918 to 1920 3% of the world population died/up to 100 million people. |
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What took place during the 1930's in regard to viruses? |
The study of viruses took place with the invention of the microscope. Could actually see them and document them |
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What are the main features of Viruses, Viroids and Prions? |
Not living agents they require a host intracellular environment they are much smaller than bacteria (nanometer scale)
For viruses: carrier or normal host-harbor the virus without symptoms Accidental host-not usual carrier, may develop disease. Example - Ebola virus. Bats are the carriers and we have accidental exposure to them, we become the accidental host... |
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What is the structure of Viruses, viroids and prions? |
Capsid - protein coat, made up of sub units called capsomers nucleocapsid - protein coat + genetic material, naked viruses - nucleocapsid is the virus enveloped viruses - nucleocapsid is covered by a lipid membrane called an envelope ( very susceptible to environmental factors) Ex. HIV virus. after a few moments of exposure to the environment it will loose effectiveness. |
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What is the taxonomic criteria based on for viruses? |
The genomic structure (the nucleic acid) whether it has RNA or DNA and if it is single stranded (SS) or double stranded (DS). either linear or circular |
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What are the virus particle structures? |
Isometric - spherical shaped (circular)
pleomorphic - ability of some bacteria to alter their shape or size in response to environmental conditions
Helical or rod shaped (linear) can also be segmented
icosahedral (20 triangles) |
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The presence of an envelope is called what |
enveloped, a lipid layer
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The absence of an envelope is called what |
naked, absence of a lipid layer |
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What do viral proteins (coat) accomplish? |
provide protection mediate adhesion give host and organ specificity some are enzymes some can act like toxins
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what is the matrix protein |
located in the inner side of envelope and mediates between the capsid protein and envelope |
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What is the viral envelope constructed of? |
Lipids and proteins it has a hybrid structure, which contains host and viral molecules the envelope gives instability to the virus. it is susceptible to soaps and lipid solvents (alcohol), environmental factors, such as heat and drying
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Enveloped viruses rely on what? |
direct transmission examples, HIV, Herpes, Hepatitis B and C |
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How do non enveloped viruses survive? |
They can only survive for a short period of time. They are more exposed to the environment. Examples, Hepititis A, Norovirus and rotavirus |
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Viral Growth Curve |
Attachment phase, number of virus acquired. falls into eclipse phase, where the virus lays dormant for a period of time (3 to 4 hours). then the log phase, where fast replication takes place. During the burst or release phase, this is when you are the most contagious. at the peak of the curve. you don't necessarily have to have a fever. |
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During the replication phase what happens to the host |
the host does not survive. replication happens fast, once the host has been used, it dies and the virus finds a new host. |
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What happens during genome replication and expression? |
the first step for replication is the production of viral mRNA. DNA viruses replicate in the nucleus. RNA viruses replicate in the cytoplasm.
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How can RNA viruses be divided up? |
The positive RNA strand virus has the genome with the mRNA. (SSRNA)
The negative RNA strand virus needs RNA ploymerase to make mRNA. (SSRNA)
Ambisense - Double Stranded RNA
Reverse transcription - where RNA produces DNA
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How does protein production happen during genome replication and expression? |
The positive strand of RNA is translated into a polyprotein, which is more than one protein translated together.
The virus proteins are separated by Virus Protease. |
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What are the steps of the Lytic cycle? |
1. The virus enters the cell 2. Hijacks the cells machinery 3. immediately initiates replication 4. the host cell ruptures after a few cycles of replication. 5. viral particles are released to infect new cells.
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What happens during the Lysogenic cycle? |
1. The virus enters the cell 2. intregrates into the host's genome and stays latent, sometimes for years 3. latency is broken when the virus switches to Lytic phase. 4. the host cell ruptures after a few cycles of replication 5. viral particles are released and infect new cells |
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At what age does Herpes simplex 1 become viable? and what are the stages of this virus? |
age 3 usually. you will see blistering around mouth and nose. once out of lytic phase, the virus will hide in the cranial nerve, neuronal cell. This is the lysogenic cycle. It will periodically resurface and go back into lytic phase. |
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what viral cycle causes disease? |
the lytic cycle, when you are most contageous |
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What triggers disease? |
cell death by the virus |
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How are animal viruses classified? |
Disease causing viruses often grouped by route of transmission.
Example would be respiratory viruses |
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How are viruses grouped or classified by route of transmission? |
enteric viruses: generally transmitted via fecal oral route, often cause gastroenteritis and some can cause systemic disease.
respiratory viruses: usually inhaled via infected respiratory droplets and generally remain localized in respiratory tract.
Zoonotic viruses: transmitted from animal to human vial animal vector ( a vector is any agent (person, animal or microorganism) that carries and transmits an infectious pathogen into another living organism.)
Sexually transmitted viruses: can cause lesions on genitalia or cause systemic infection. |
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How do animal viruses interact with accidental hosts? |
the outcome of infection of eukaryotic cells depends on factors independent of the cell and the defense mechanisms of the host.
the relationships are divided into two categories:
1. acute: only lytic cycles. an example would be measles. once you've had the disease you won't get it again.
2. persistent: only lysogenic cycles. |
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How do animal viruses interact with their normal hosts? |
Normal host: no obvious disease or damage is caused to host.
there is a state of balanced pathogenicity.
example: lassa fever carried by rodents
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Explain the interactions of animal viruses with their hosts in regard to an acute infection. |
acute infections are usually short in duration. the host may develop long lasting immunity. results in productive infections, which means it produces large number of viruses during replication. The disease symptoms result from tissue damage and infection of new cells. |
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list the process of animal virus replication |
1. attachment 2. entry 3. targeting 4. uncoating, which exposes the nucleic acid 5. replication and synthesis 6. maturation 7. cell lysis 8. spreading within the host 9. shedding and transmission |
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Explain the interactions of animal viruses with their hosts in regard to a persistent latent infection. |
after initial infection, virus replicates in neurons in non-infectious state. Then virus is activated to produce new symptoms. Example: Chicken pox to zoster or shingles |
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Explain the interactions of animal viruses with their hosts in regard to a persistent chronic infection. |
after initial infection with or without disease symptoms, infectious virus is release from host with no symptoms. you are always contagious with a chronic infection. Example: Hep B and C With a chronic infection you have both lytic and lysogenic cycles happening simultaneously. |
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Explain the interactions of animal viruses with their hosts in regard to a persistent slow infection. |
slow developing disease. transmissible agents multiply without resulting in disease symptoms until they cause a fatal infection. Example: HIV becoming the aids virus after many years. |
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Where does the virus stay during the latent or dormant phase. |
it migrates and resides in the ganglia of the neck area. will show up in certain areas depending on which ganglia it resides in. Stress levels can activate a virus to migrate to the skin |
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protein can only be formed from |
RNA+ or messenger RNA |
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Review diagram on page 076 |
Single stand and double strand replication |
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Acute infections (Animal viruses with their host) |
Usually short in duration. host may develop long-lasting immunity. result in productive infections (produce large number of viruses during replication). disease symptoms result from tissue damage and infection of new cells. Example: measles
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Persistent infections are categorized how? |
1. latent 2. chronic 3. slow |
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Give the steps for animal virus replication Lytic cycle |
1. attachment 2. entry 3. targeting 4. uncoating (exposing nucleic acid) 5. replication and synthesis 6. maturation 7. viral release 8. spreading- within the host 9. shedding and transmission
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Animal virus replication-latency |
1. attachment 2. entry 3. targeting 4. uncoating --> 5. latency established 6. reactivation 7. replication and synthesis 8. maturation 9. viral release 10. spreading - within host 11. shedding and transmission |
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describe and give an example of a persistent latent infection |
the infection is followed by symptomless period, then reactivation. infectious particles not detected until reactivation. symptoms of reactivation and initial disease may differ. Example: herpes simplex viruses 1 and 2. after latent period may develop into shingles. |
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describe what happens with herpes simplex 1 latent infection and the development of a cold sore. |
first, the initial infection occurs in 3 to 5 year old children. with fever, soar throat, fever blister. It then moves into the trigeminal nerve and becomes dormant or latent in the sensory ganglia of the nerve. |
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describe what happens when the herpes virus is reactivated later in life. |
the virus becomes reactivated and travels back down the nerve and causes cold sores. |
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describe a persistant chronic infection |
infectious virus can be detected at all times. the disease may be present or absent during extended times or may develop late. example: hepatitis b (serum hepatitis) |
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describe slow persistant infections |
infectious agent increases count slowly over long period of time and no significant symptoms apparent during this time.
two groups of infectious agents cause slow infections.
examples: retroviruses (HIV) and prions |
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double stranded DNA viruses are responsible for most virus induced tumors in humans, how? |
20% of viral infections become cancer. cancers caused by DNA viruses result from integration of viral genome into host DNA, changing the make-up of the host DNA. you have uncontrolled growth results.
Examples: kaposi's sarcoma (HSV8 - cancer of the connective tissue) EBV - burkitt's lymphoma, nasopharyngeal carcinoma (back of throat, nose), B cell lymphoma HPV - cervical CA Hep B and C - liver HTLV-1 - T cell lymphoma (retrovirus)
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a culture prepared directly from an animal host is called |
primary culture |
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How are viruses cultivated |
viruses only multiply inside host cell. host cells are cultivated in the laboratory in cell culture or tissue culture. |
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What are prions? |
proteinaceous infectious agent they are linked to a number of fatal human diseases. They are always fatal. they always affect the central nervous system. It causes brain degeneration with sponge-like holes. the disease is transmissible and called spongiform encephalopathies symptoms include: dementia, comma and then death |
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Examples of prion diseases |
scrapie agent - the host is sheep (scrapie spongiform encephalopathy) kuru agent - the host is humans (kuru spongiform encephalopathy) creutzfeidt-jacob agent - the host is humans (creutzfeidt-jacob disease) mad cow agent - the host is humans and cows (mad cow spongiform encephalopathy) chronic wasting disease agent - the host is deer and elk (chronic wasting disease) transmissible mink agent - the host is ranched mink (transmissible mink encephalopathy) |
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Do prions replicate? |
No. They convert normal proteins into prions. they affect the Tertiary structrue of a protein. mutation caused otherwise normal host protein to have different folding properties. they are resistant to proteases. they are resistant to UV & nucleases because of their lack of nucleic acid. inactivated by chemicals that denature proteins. very tough to kill. surgical equipment has to be discarded.
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describe viroids |
smaller than viruses. replicate autonomously in susceptible cells. single viroid capable of infecting a cell. small circular ss RNA molecule and resistant to RNAses. vary in length. have no protein coat and resistant to proteases.
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What do viroids infect? |
all indentified viroids infect plants examples: potato spindle tuber, chrysanthemum stunt, cadang-cadang (coconuts, do not produce coconut water) when it affects agriculture, the land has to be free of plant with viroids for 25 years to clear it. |
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How can viral vectors be used for therapeutic value |
adenoviruses for gene therapy which allows the replacement of mutated genes in humans promising results for cystic fibrosis. a good copy of the virus is inserted, which could rectify the disease entirely. the symptoms will revert
genetically engineered vaccines. viruses that can immunize against malaria. |
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Some viruses contain regulatory proteins in a structure called the _____. Where is it located and what do they do or accomplish? |
Tegument they are located between the nucleocapsid and the envelope. they include transcription and translation factors that control either viral or cellular processes.
Example: herpes simplex virus and cytomegalovirus |
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The envelope is comprised of what type of protein? |
lipoprotein lipid derived from the host cell membrane and protein that is viral specific. |
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What are the spike like projections found on viruses comprised of? |
glycoproteins |
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What does the matrix protein do? |
mediates the interaction between the capsid protein and the envelope. |
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the capsid is composed of repeating subunits called: |
capsomers |
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typically the envelope is acquired as the virus exits from the cell in a process called |
budding |
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what is a virion? |
the complete, infective form of a virus outside a host cell, with a core of RNA or DNA and a capsid. |