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48 Cards in this Set
- Front
- Back
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Describe viral chromosome structure. |
Viruses can be DNA, RNA, single stranded, or double stranded, linear, or circular. It can do it all! |
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What is the difference between a virion and a virus? |
Virus is the infected cell whereas virion is the infecting particle |
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Virions may have a wide range of sizes, shapes, and chemical compositions, however they always have a _____ geometric pattern. Either ___ or ____ |
Regular, rods with helical symmetry or spheres with icosahedral (20 faces) symmetry |
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What virus structures are unique to bacteriophages. Describe this structure |
Complex viruses with a head, tail, and tail fibers |
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What type of virus is a common infectious agent of animals and humans? What is the purpose of being in this form and where do the viruses get the materials to do it? |
Enveloped viruses have an outer layer of membraneous material outside the capsid which is attains from the host cell to mask the foreign nature |
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What is the difference between a capsid and nucleocapsid? |
Capsid = Coat + Shell
Nucleocapsid = Capsid + Genome |
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What is the basic subunit of a virions capsid? |
Capsomeres |
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What enzymes function in penetrating the cell? |
Neuraminidase breaks down glycolipids = connective tissue of cells Lysozyme breaks down peptidoglycan and releases virions from the infected cell |
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What 3 can we methods use to harvest viruses? |
1) Infect Bacteria to cultivate bacteriophages 2) Infect Chicken embryos 3) Infect Tissue cultures |
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How do we do viral quantification? What is the unit of viral concentration? |
Plaque assay where we infect a lawn of cells from a known dilution. After a finite incubation period plaques form each representing a plaque forming unit. The titer is the concentration of virus |
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What are the 7 steps of viral reproduction? |
1) Attachment (Adsorption) 2) Penetration (Injection) 3) Early steps in replication where we alter host cell machinery 4) Replication of viral genome 5) Structural protein synthesis 6) Assembly/Packing into capsids 7) Release |
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What does the host supply to the virus? |
1) Energy-generating systems 2) Ribosomes 3) Amino Acid activating enzymes 4) tRNA 5) Soluble factors |
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What is required for attachment of a virus? Is this the only way to enter a cell? |
Viral proteins that interact with host cell surface receptors. Some viruses can enter via phagocytosis, endocytosis, or cell membrane fusion |
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What dictates if the whole virion enters the cell or just the genomic code? |
Host cells that lack cells walls are often penetrated by the whole virion |
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How do prokaryotes deal with infection from viruses? |
They use restriction enzymes to degrade foreign DNA |
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How do bacteriophages prevent excision by bacteria? |
They glucosylate and methylate after replication has occured |
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What are all viral protein made from? |
Viral-specific mRNA |
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The nucleic acid strand that is translated into protein is known as having what configuration? What configuration do we assign the complimentary strand? This also works for DNA |
positive configuration aka mRNA+/DNA+ for the translated strand whereas the complimentary strand is -mRNA/-DNA |
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When does it matter if we translate the positive or negative configuration of the viral nucleic acid strands? |
If the viral nucleic acid is not dsDNA or mRNA+, these configuration must be synthesized |
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Production of DNA from RNA is known as ____ _____ and is catalyzed by the ______ ______ enzyme |
Reverse transcription via Reverse transcriptase |
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What are the catagories of viral proteins? How do they differ? |
Early Proteins: Produced soon after infection and are needed for replication. Synthesized in small batches Late proteins: Produced following early proteins and include proteins of the virus coat. Synthesized in large batches |
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Describe the chromosomal structure of most RNA bacteriophages. |
Most are ssRNA, small, icosohedreal, and have 180 copies of coat protein per particle |
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What is the best characterized RNA bacteriophage and tell me about it's chromosomal structure. |
MS2 is the best characterized, it has mRNA+ such that the viral mRNA is translated directly. Has only 4 genes and a lot of overlapping regions which is common of small genomes |
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What are the 4 types of Bacterial Viruses and what are their protoyptical examples. |
1) RNA - MS2 2) ssDNA - X174 3) dsDNA - T viruses aka Lytic viruses 4) Temperate and Lysogeny |
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What virus is a major tool in genetic engineering. Describe it's replicative form? What is the purpose of this form? |
X174 is the major tool.Before replication occurs, X174 converted into a double-stranded replicative form from it's native +ssDNA. Fromthese, single-stranded genome copies are derived via rolling circle replication |
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How do the T-odd (T1, T3, etc.) and T-even (T2, T4, etc) phages differ? What do they have in common? |
T-odd have short tails T-even have long tails They both have heads, tails, tail fibers, and linear DNA |
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Lysogeny is a state that occurs in temperate phages. What is a temperate phage and what is lysogeny? |
Temperate phase is a virus that kills their host under some circumstances but not others. Lysogeny is the state in which viruses do not produce progeny and the virus genome is replicated in synchrony with the host chromosome. |
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What organisms undergo lysogeny and when is it triggered. |
Lysogeny occurs in bacteriophages and is induced when a virus genome is integrated into the bacterial genome. |
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Define prophage. What is the effect on an organism of having a prophage? How do we maintain this state? |
Virus integrated into a chromosome is a prophage which confers immunity preventing reinfection by other viruses of the same type. The prophage state is maintained by a repressor molecule that binds to the viral DNA in the bacterial chromosome.
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What happens when the prophage repressor molecule fails to bind its recognition sequence? |
The prophage undergoes the lytic cycle whereby it produces progeny virions and lyses the cell |
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What is a cryptic virus? |
A phophage that has lost its ability to exit the lysogenic cycle and is permanently carried as a prophage in the bacterial genome |
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Animal virus infection can result in 4 effects that we need to know for the test. What are they? |
1) Transformation of normal cells into tumor cells 2) Lysis of host cell causing host cell death 3) Persistent infection leading to chronic disease and shedding of virions 4) Latent infection resulting in asymptomatic period with no evidence of viral presence |
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Disregulation in what 2 types of genes can lead to uncontrolled cell growth and cancer? Viruses can cause cancer via what mechanisms? |
Proto-oncogenes which promote cell growth and division Tumor suppressor genes which restrain cell growth and division Viruses can activate proto-oncogenes and mutate/deactivate tumor suppressor genes |
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What 3 viruses have a strong relationship with tumorigenesis? |
Papilloma - Cervical and skin cancers Hepatitis B - Hepatocellular carcinoma (liver) Epstein-Barr - Nasopharyngeal carcinoma |
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What are the 7 types of human viruses? |
1) Positive Strand RNA 2) Negative strand RNA 3) dsRNA 4) ssDNA 5) dsDNA 6) Retroviruses 7) Viroids and Prions |
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How do you classify the family of viruses that includes rhinovirus, heptaitus A, and polioviruses? What is the name of this virus family. Describe their genome. |
Picornavirus includes the other viruses. It is a RNA+ genome thus the RNA acts directly as mRNA |
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What class of viruses are all enveloped, all ssRNA, and all use virally encoded RNA Pol? What 3 major viruses are included in this? |
Negative-strand viruses. RNA is transcribed into complementary strand to make mRNA.
1) Rhabdovirus 2) Influenza virus 3) Filovirus |
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What is the causative agent of rabies? Describe it's morphology. What class of animal virus is this? |
Rhabdoviruses which are rob shaped and are part of the negative-strand RNA viruses |
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What member of the orthomyxoviruses has no defined shape, a segmented genome, and can result in a major epidemic should an antigenic shift occur. What is a segmented genome and what is an antigenic shift. |
Influenza virus! Segmented genome = the genome has 8 fragments similar to having 8 chromosomes Antigenic shift is when the RNA from 2 different strains infect the same host, mix, and are repackaged leading to a new infectious strain |
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What family of viruses includes ebola? Describe it's morphology. Describe it's chromosomal structure. |
Filoviruses include ebola and are filamentous hemorrhagic viruses of the non-segmented ssRNA- type |
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The 2014 ebola outbreak was due to a variant of what virus? |
EBOV Zaire |
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How long is the replication cycle of ebola zaire? How long do it's cytopathic effects (structural changes in the host cells that are caused by viral invasion) take to set it? What is the incubation period. How is it spread? |
12 hours to replicate 48 hours for cytopathic effects 2-21 day incubation period Spread via infected body fluids, blood/lymph/sweat/tears/saliva, etc |
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What is the only dsRNA virus? This is a common causative agent in what pediatric pathology? |
Reoviruses are the most common causative agents of infant diarrhea |
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What is the only ssDNA virus? What is it's relevance? |
Parvovirus is an important pathogen in animals |
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What class of animal viruses include both enveloped and non-enveloped icosahedral viruses that are of human medical importance? What are 3 viruses in this catagory? |
dsDNA which includes adenoviruses, herpes viruses, poxviruses |
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What does the adenovirus do? |
Acute respiratory diseases in humans |
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What virus is ssRNA+ and replicates via a dsDNA intermediate. What molecule facilitates this? Give an example of this virus |
Retroviruses are ssRNA+ and they use reverse transcriptase causing HIV. |
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What are viroids? Tell me about the genome. |
Naked RNA without a capsid. No genes are encoded by the RNA and it is circular ssRNA |
