Chapter 10 Viruses – Flashcards
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| Obligate intracellular parasite |
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| Organisms that MUST use a cell to replicate. Includes: viruses, chlamydias, rickettsias |
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| Capsid |
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| A viral component made of protein and that surrounds the virus' nucleic acid. |
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| Envelope |
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| A membrane that surrounds some viruses made of lipid bilayer. |
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| Virion |
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| A complete virus particle, which includes an envelope, if it has one. |
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| Genome |
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| Genetic information |
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| Capsomeres |
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| Protein subunits that are part of the protein capsid that surrounds a virus. |
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| Enveloped viruses |
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| Viruses that have a bilayer membrane outside their capsids. Viruses that have no bilayer membrane are "naked". |
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| Nucleocapsid |
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| Comprises the viral genome together with its capsid. |
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| Naked |
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| A virus with only a nucleocapsid but no envelope, or non-enveloped viruses |
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| Glycoproteins |
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| The substance that makes up the spikes that are projections found on the envelopes of certain enveloped viruses. |
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| Spikes |
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| Projections on the envelope of certain enveloped viruses. Certain spiked viruses cause RBCs to clump. Useful in virus identification. |
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| Complex viruses |
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| Viruses with more elaborate coats or capsids. |
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| Bacteriophages |
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| Viruses that infect bacterial cells. They have specialized heads, tails, and tail fibers. The tail fibers are the spikes that the virus uses to attach to the host bacterium. |
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| Host range |
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| The spectrum of hosts that a virus can infect. |
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| Viral specificity |
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| Refers to the specific type of cells that a virus can infect. |
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| Positive (+) sense RNA |
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| One of two types of single-stranded RNA viruses. Positive sense RNA acts like mRNA and can be translated by the host's ribosomes. |
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Negative (-) sense RNA
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| One of two types of single-stranded RNA. Negative sense RNA acts as a template during transcription to make a positive (+) sense RNA (acts like mRNA) AFTER a host cell has been entered. From there it can be translated by host ribosomes just like positive (+) sense RNA can. |
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| Enteroviruses |
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| entero, Greek for "intestine", are viruses that can live in the intestine of the host. |
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| Hepatoviruses |
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| hepato, Greek for "liver", viruses that infect the liver. |
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| Rhinoviruses |
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| rhino, Greek for "nose", is one genera of viruses responsible for the common cold. |
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| Reverse transcriptase |
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| The enzyme used by retroviruses to do reverse transcription where they use their RNA to make dsDNA. It's called reverse transcription because it is the reverse of the typical transcription step where normally DNA -; RNA in protein synthesis. |
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| Retroviruses |
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| Enveloped viruses that have two complete copies of (+) sense RNA with which they can do reverse transcription. |
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| Provirus |
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| Viral DNA that has been incorporated into the chromosomes of the host DNA. |
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| togaviruses |
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| small, enveloped, polyhedral, (+) sense RNA viruses that multiply in the cytoplasm of many mammalian and arthropod host cells. |
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| Flaviviruses |
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| Enveloped, polyhedral, (+) sense RNA viruses that are transmitted by mosquitoes and ticks. |
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| paramyxoviruses |
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| medium-sized, enveloped, (-) sense RNA viruses with a helical nucleocapsid. |
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| Rhabdoviruses |
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| medium-sized, enveloped viruses, whose capsids are helical and so are rod or bullet shaped. |
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| orthomyxoviruses |
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| medium sized, enveloped, (-) sense RNA viruses that vary in shape and whose genome is segmented into eight pieces. i.e. influenza virus A. |
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| filoviruses |
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| Enveloped, filamentous, single (-) sense RNA viruses that can be transmitted from person to person by close contact with blood, semen, and other secretions and by contaminated needles. I.e. ebola. |
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| Bunyaviruses |
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| Enveloped, (-) sense RNA viruses whose genome has three segments. Transmitted by arthropods. |
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| Arenaviruses |
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| Enveloped, (-) sense RNA viruses, but their genome has two segments. Carried by rodents. Passed among humans via aerosols or exposure to rat bites or excrement. |
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| Reoviruses |
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| naked, polyhedral capsid, medium-sized dsRNA viruses that replicate in the cytoplasm and form distinctive inclusions that stain with eosin. Includes: orthoreoviruses, orbiviruses, rotaviruses. |
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| Adenoviruses |
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| Medium-sized, naked, viruses with linear dsDNA that are resistant to chemical agents and are stable from pH 5 to 9 and from 36 degrees celsius and 47 degrees celsius |
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| Herpesviruses |
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| herpes, Greek for "creeping", relatively large, enveloped viruses with linear dsDNA that cause a broad spectrum of diseases. Tendency to go latent between relapses. |
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| Latency |
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| The ability of viruses, like the herpes virus, to remain in host cells, usually in neurons, for long periods and to retain the ability to replicate. |
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| poxviruses |
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| A group of enveloped viruses with linear dsDNA that are the largest and most complex of all viruses. Can infect nearly every animal species. They replicate in parts of the host cell's cytoplasm called viroplasm. |
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| Papovaviruses |
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| Small, naked, polyhedral dsDNA viruses that replicate in the nuclei of the host cells. Includes: papilloma, polyoma, vacuolating viruses |
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| Hepadnaviruses |
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| Small, enveloped, mostly dsDNA (partially ssDNA) viruses. They cause liver infection. |
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| parvoviruses |
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| Small,naked, linear ssDNA viruses. Their genetic information is so limited that they must enlist the aid of an unrelated helper virus or a dividing host cell to replicate. Three genera: dependovirus, parvovirus, erythrovirus. |
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| Emerging viruses |
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| Recently discovered and unexpected viruses that were previously endemic but that has expanded its host range to become potential pandemic. |
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| Phage therapy |
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| The use of phages aka bacteriophages (viruses that infect bacteria) to treat bacterial disease. |
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| Replication cycle |
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1. Absorption - virus attaches to host cell 2. Penetration - entry of virions or their genome into host cell 3. Synthesis - Use of cell machinery to make new parts 4. Maturation - assembly of viral the synthesized components 5. Release - departure of new virions from host cell. |
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| Virulent (lytic) cycle |
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| Phages that lyse its host cell upon release of new viruses. |
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| Lytic cycle |
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| The replication process of the type of viruses that end with the lysing of the host cell. |
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| Burst time |
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| Time from absorption to release of a virus' lytic cycle. |
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| Viral yield aka burst size |
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| The number of new virions released from each bacterial host. |
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| Replication curve |
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| Curve that describes and represents viral growth which includes an eclipse period (penetration through biosynthesis) and a latent period (from penetration through phage release). |
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| Plaque assay |
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| A way for virologists to estimate phage number using serial dilutions and inoculating them onto a series of plates containing a susceptible bacterial lawn (a layer of bacteria). After incubation the plaques are counted since they represent the areas where viruses have lysed host cells. |
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| Plaques |
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| Each plaque represents the progeny from one infectious phage... such counts are reported as plaque-forming units (pfu). |
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Plaque forming units (PFU) |
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| The estimate count of phages based on the number of plaques seen on a plate |
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| Temperate phages |
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| Bacterial attacking viruses that do not necessarily undergo a lytic cycle with its host |
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| Lysogeny |
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| A stable, long-term relationship between a phage and its host in which the phage nucleic acid becomes incorporated into the host nucleic acid |
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| Prophage |
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| Is the viral DNA within the bacterial chromosome placed there by the phage during its lysogenic state |
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| Lysogen |
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| The combination of a bacterium and a temperate phage |
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| Lysogenic conversion |
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| When "immunity" is given to a lysogen by its phages that "protects" it from other phages of that same type (same DNA) |
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| Lysogenic cycle |
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| The growth of lysogens, meaning, when a bacterial host with phage DNA in its chromosomes undergoes its binary fission the phage DNA gets replicated along with its own and passed down this way. If the phage activates the lytic cycle in any of the daughter cells will by lysed by these phages when they break out. |
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| Induction |
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| The term used for when a dormant phage becomes active and initiates the lytic cycle. Reasons: lack of nutrients, presence of chemical toxins, or some other reason for the virus to seek greener pastures elsewhere |
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| Uncoating |
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| When the viral genome of an animal virus separates from its protein coat so it can enter the host |
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| Monolayers |
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| a layer of cells one cell thick that is spread on a plastic surface. It is used for culturing animal viruses. |
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| Subculturing |
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| The process by which cells from an existing culture are transferred to new containers with fresh nutrient media |
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| Tissue culture |
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| AKA cell culture: The technique of sub-culturing animal tissue for the study of animal viruses |
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| Primary cell cultures |
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| are cultures obtained directly from the animal and are not subcultured |
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| Cell strain |
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| What is produced from a primary cell culture when it is repeated and one type becomes dominant |
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| diploid fibroblast strains |
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| Immature animal cells that produce collagen and other fibers as well as the substance of connective tissues, such as the dermis of the skin... derived from fetal tissue they retain the ability to divide rapidly |
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| continuous cell line |
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| cells that will reproduce for an extended number of generations, i.e. the HeLa cell line which has been maintained and grown in culture since 1951 and has been used in research world wide |
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| cytopathic effect (CPE) |
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| The visible effect viruses have on cells |
