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55 Cards in this Set
- Front
- Back
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contagium vivum fluidum |
a contagious fluid |
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Virus |
- latin for poison - semi-living: have only some of the characteristics of life - no metabolism - able to reproduce only with considerable help from host cell - no ribosomes - no plasma membrane - obligate intracellular parasites - high mutation rate |
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Viruses and Bacteria compared |
check |
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Obligate Intracellular Parasites |
require living host cells to multiply - will not grow on artificial media - do exist outside of host cells (ex.) some are transmitted through the air |
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Size of Viruses |
small: 20-1,000 nm |
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Virus Structure |
- no cells - neither prokaryotic or eukaryotic |
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Virion |
- complete, fully developed, infectous viral particle composed of a nucleic acid and surrounded by a protein coat outside a host cell - individual unit, virion is to a virus as cell is to a unicellular organism |
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Capsid |
- nucleic acid of a virus protected by a protein coat, structure determined by viral nucleic acid and accounts for most of the mass of a virus - protects the genome and gives shape to a virus |
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Capsomeres |
- individual protein subunits that make up a capsid |
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Genome |
core of nucleic acids - either DNA or RNA never both - either single or double stranded |
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Host range |
- the species that a pathogen can infect - most viruses are host specific: infect only one or a few species of hosts - most are tissue specific (infect only one kind of host tissue) |
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Bacteriophages or PHAGE |
- viruses that infect bacteria -receptor part that bacteriophages may interact with is part of the cell wall of the host - can wipe out a bacterial culture - they often make the bacteria they infect more pathogenic for humans |
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Viral Replication (Reproduction) in ANIMAL Viruses |
1. Attachment of host cell: Virus penetrating host cell 2. Entry or Pentration: into host cell - either whole virus or just nucleic acid (protein and envelope may be left behind) - either into cytoplasm or nucleus of host cell 3. Biosynthesis A. Replication of viral nucleic acid (may dissolve host genes to get ingredients) B. Synthesis of viral protein: viral genes take control of host ribosomes and direct synthesis of viral protein 4. Maturation: assembly of new virions - up to several hundred 5. Release: of new virions - enveloped viruses escape one by one, taking along some cell membrane for their envelope (a budding process) = host cell may survive - other viruses may rupture host cell to escape |
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Phage replication |
20 to 40 minutes = 50 to 200 new phages emerge |
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Spikes |
- carbohydrate-protein complex that project from the surgace of the envelope, used for attachment - can be used as a means of identification |
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Viral Species |
- group of viruses sharing the same genetic information and ecological niche (host range) - specific epithets for viruses aren't used, viral species designated by descriptive common names, with a subspecies designated as a number |
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Example of a Viral Species |
Family: Herpesviridae Genus: Simplexvirus Human Herpes Virus 2 |
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Taxonomy of Viruses |
- oldest classification of viruses based on symptomatology: based on what disease they cause - Based on nucleic acid, strategy for replication, and morphology Genus -virus Family -viridae Order -ales Ex. Family Herpesviridae, genus Simple Virus |
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How are bacteriophages cultured? |
can be grown either in suspensions of bacteria in liquid media or in bacterial cultures on solid media 1. Bacteriophage sample mixed with host bacteria and melted agar 2. Agar containing bacteriophages and host bacteria is poured in a Petri plate containing a hardened layer of Agar growth medium 3. Virus-bacteria muxture solidifies into a thing top layer that contains a layer of bacteria approx. one cell thick 4. Each virus infects a bacterium, multiplies, releases more viruses 5. Infects other bacteria in immediate vicinity 6. All bacteria surrounding originial virus are destroyed produces clearings of "plaques" visible against a lawn of bacteria growth on surface of agar |
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How are animal viruses cultured? |
1. In living animals (mice, guinea pigs), animal inoculation may be used as a diagnostic procedure for identication/isolating virus - its diff to use animals as test subjects for human disease because some human viruses can't be grown in animals or can be grown but dont produce disease |
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How are animal viruses cultured |
s |
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Lysogeny |
Host's DNA not destroyed and viral genome remains inactive in the cell - hibernating virus for generations... then excised later to a lytic virus - many bacteria that infect humans are lysogenized by phages |
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Retrovirus (ex. HIV) |
Retroviridae, genus: Lentivirus, HIV - carry their own enzyme (reverse transcriptase) - uses viral RNA to synthesize DNA (reversal of the usual biochemical direction) in host cell |
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Provirus |
Newly synthesized viral DNA integrated into host cell's chromosome by a Retrovirus - can produce viruses or transform a host cell, can be activated by a catalyst such as UV light |
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Techniques used to Identify Viruses |
1. Serological methods 2. Observation of cytopathic effects 3. PCR (polymerase chain reaction) 4. RFLP's (restriction fragment length polymophisms) 1. inoculate viruses into fertilized eggs and lok for characteristic changes due to viral replications 2. search for antibodies in patient's serum (serological tests) 3. look for pathological signs in the diseased tissue |
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Lytic Cycle (ends in lysis and death of host cell) |
- the virions of T-even bacteriophages are large, complex and nonenveloped 1. Attachment: Phage attahes to host cell 2. Penetration: Phage penetrates host cell and injects its DNA 3. Biosynthesis: Phage DNA directs synthesis of viral components by the host cell 4. Maturation: Viral componenets are assembled into virions 5. Release: Host cell lysis and new virions are released |
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Lysogenic Cycle (doesn't cause cell lysis) |
- lysogenic phages or temperate phages Three Results of Lysogeny 1. Immunity to reinfection by the same phage 2. Phage conversion --> new properties 3. Specialized Transduction --> Bacterial genes picked up by phage coat and transferred to another bacterium |
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Lysogeny |
phage remains latent or inactive |
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Lysogenic Cells |
participating bacterial host cells |
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Why are viruses difficult to control? |
due to few vulnerabilities of viruses: few structures, no metabolism |
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List ways viruses are inhibited |
1. Our body defenses 2. Antiviral drugs of limited value 3. Interferons: antiviral proteins produced by human cells in response to viral infection (protect healthy cells from viral damage by blocking various steps in viral replication) 4. viral vaccines: best method of controlling viruses at the time - Inactivated - Activated |
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Viruses and Cancer (1908 chicken leukemias) |
- cancer results from the uncontrolled reproduction of cells - certain chemicals are carcinogens (cancer causing) - cigarette smoke, asbestos, pesticides, dyes, environmental pollutants, UV/X-ray, including VIRUSES - some human (and many animal cancers) are known to be caused by viruses (oncogenic viruses) - approx. 10% of cancers are virus induced |
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Prions |
- infectious particles of protein only; no nucleic acid - associated with degenerative diseases of human nervous system/brain tissue - resistant to disinfection, heat and autoclaving EX. bovine spongiform encephalopathy - named for brain's appearance (mad cow disease from consumption of contaminated beef) |
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Oncogene |
- influence cellular growth to a higher than normal rate - causes tumors |
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Viroids |
- infectious particles of naked RNA only; no protein - 1/10 size of average virus - only associated with Plant diseases |
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Oncogenic Viruses |
viruses capable of inducing tumors in animals |
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Oncolytic Viruses |
infect and lyse cancer cells (destroys them) - these viruses are being genetically modified to take out virulence and instead add genes that promote white blood cell growth - ie. adenovirus, Simplexvirus, vaccina virus |
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Latent Viral Infection |
- some viruses enter host cell and remain dormant or replicate slowly with little damage to host cell - may activate later upon some stimulus ie. immune response, sunburn - ex. Leukemia, Cold sores |
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Persistent Viral Infection (or Chronic Viral Infection) |
- a viral infection that occurs gradually over a long period, typically fatal GAT DAM T-T - differs from a laten infection in that, detectable infectious virus gradually builds up over a long period, rather than appearing suddenly - ex. Cervical cancer, HIV/AIDS |
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Enveloped Virus |
- virus where the capsid is covered by an envelope, usually consists of some combination of lipids, proteins and carbohydrates. - determined by viral nucleic acid, materials derived from normal host cell components - may be covered with spikes that project from the surgace of the envelope |
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Nonenveloped Virus |
Viruses who capsids aren't covered by an envelope. - Capsid of a nonenveloped virus protects the nuclic acid from nuclease enzymes in |
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How does influenza cross the species barrier? |
- due to antigenic drift, when a different strains for a virus from different species infect the same host and end up mixing their genes |
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Vibrio cholerae produces toxin and is capable of causing cholera only when it is lysogenic. What does this mean? |
This means that Vibriocholerae is able to produce toxin and cause cholera thanks to a prophage which carries the gene coding for the toxin. |
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Oncogene |
a gene that can turn a cell into a tumor cell
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Transformed Cell |
- tumor cells that have undergone transformation and have acquired properties distinct from the properties of uninfected cells - contain a virus specific antigen Tumor-Specific Transplantation ANtigen (TSTA) on cell surface or an antigen in their nucleus called the T antigen |
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Is Shingles a persistent or latent infection? Explain. |
Shingles is considered a latent infection because changes in the immune (T cell) response activate latent viruses to cause rashes to appear on skin along the nerve in which the virus was latent |
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Discuss how a protein can be infectious |
1. PrPc produced by cells is secreted to the cell surface. 2. PrP Sc acquired or produced by an altered gene. 3. PrP Sc reacts with PrPc on cell surface which converts it to PrP Sc. 4. This conversion goes on until PrP Sc is taken into the cell through endocytosis. 5. PrP Sc endosomes accumulate and are transferred to lysosomes which results in cell death. If an abnormal prion protein (PrP Sc) enters a cell, it changes the normal prion protein to PrP Sc, which now can change another normal PrPc, resulting in an accumulation of the abnomal PrP Sc and cell death, |
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Differentiate between virus, viroid, and prion |
Virus - badbadbad Viroid - infectious pieces of RNA that cause some plant diseases Prion - infectious proteins, Prion diseases result of an altered protein |
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Viruses ARE living organisms |
Nucleic acid are active inside a host cell, from a clinical point of view they are living because they cause infection and disease, just as pathogenic bacteria, fungi, and protozoa do./ |
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Viruses AREN'T living organisms |
Nucleic acid of living cells are in action all the time BUT - they are inert outside of living host cells |
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What's the latest on the influence (flu) viruses? |
- nasal spray not used for 2016-2017 - flu activity is low, but will increase in upcoming weeks - yearly flu vaccine for everyone 6 months and odler |
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What does the H and N represent in H1N1? |
Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N).
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Discuss the relationship between DNA-containing viruses and cancer |
Adenoviridae, Hepesvirida, Poxyvirdiae, Papovaviridae
- Epstein-Barr (EB) virus ability to cause cancer accidentally demonstrated when a boy named David died from cancer after receieving a bone marrow transplant :{ |
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Discuss the relationship between RNA-containing viruses and cancer
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- only Retroviridae cause cancer - contain oncogenes or contain promoters that turn on oncogenes or other cancer-causing factors - ie. human T cell leukemia viruses (HTLV-1 and HTLV-2) |
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Draw that big chart out with examples and their different characteristics. |
DO IT 12 points bruhhh |
