Microbiology Final- Chapter 13 (Viruses) – Flashcards

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viruses are _______ outside the cell
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Complex Chemicals
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Viruses are _______ within live cells
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living entities
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are viruses composed of cells?
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no!
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are viruses made up of nucleic acid?
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yes, SINGLE nucleic acid (DNA OR RNA) surrounded by protein coat
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viruses are what type of parasites?
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viruses are obligate intracellular parasites (as are some bacteria-table 13.1)
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how do viruses multiply
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by using cells' synthetic machinery!
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what range of diameter do Viruses have?
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20nm and up!
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what length do viruses have?
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20-1000 nm
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Host range=__________
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organisms that viruses infect
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what 3 hosts do viruses infect?
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plants, animals, and bacteria
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what is an example of a plant virus?
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TMV- Tobacco Mosaic Viruses
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what is are four examples of animal viruses?
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Herpes, influenza (flu) virus, poliovirus and rabies virus
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Genome=
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viral nucleic acid (NA)
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Capsid=
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viral protein coat- fig 13.2
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Capsomere=
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protein subunits of the capsid
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Nucleocapsid=
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NA + capsid
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Virion=
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complete, fully developed, infectious viral particle.
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The viral nucleic acid (genome)-can be:
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1.DNA or RNA (never both in a VIRION)!
2. Non-segmented or segmented
3. Linear or circular
4. Double or single stranded
5. Single stranded genome:
-Is a sense or (+) strand if it behaves like mRNA
-Is antisense or (-) strand if it can't act like mRNA
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when is a single-stranded genome a sense (+) strand?
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if it behaves like mRNA!
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when is a single-stranded genome a antisense (-) strand?
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when it can't behave like mRNA
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Viral morphology (shape) is:
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based on capsid architecture
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Viral Morphology- Helical viruses:
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-long or curved rods/ threads
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What is an example of a Helical virus?
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TMV, rabies virus, ect.
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Viral Morphology: Polyhedral viruses:
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Icosahedrons structure (many sided)
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what is an example of a polyhedral virus?
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Adenoviruses, and picornaviruses
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Viral Morphology: Enveloped Viruses:
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Envelope surrounds the capsid, is derived from cellular membranes
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what is an example of and enveloped helical virus?
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Influenza virus
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what is an example of an enveloped polyhedral virus?
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herpes simplex virus
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Viral Morphology: Complex viruses:
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Have complex structure!
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what is an example of a complex virus?
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T-even phages (T2 and T4) and poxviruses (smallpox virus and cowpox virus).
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Viral Taxonomy is what?
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viral classification!
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Viral Taxonomy is based on what 3 things
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nucleic acid type, morphology and replication strategy (retrovirus-HIV example)
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Viral Taxonomy-family, genus/species names:
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-Family suffix is viridae ex) retrovirade
-Genus suffix is virus ex) lentivirus
-Species: a descriptive name ex) HIV
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Growing Viruses in the Lab:

1.Bacteriophages
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Example-T4 grown in E. coli:
-Lawn of E.coli on AGAR + T4-> areas of clearing on agar, called PLAQUES!

-BROTH culture of E. coli + T4-> CLEARING of broth is an indication of T4 growth!
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Growing Viruses in the Lab:

2.Animal viruses-where can they be grown in?
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1.Lab animals
2.Embryonated eggs
3.Cultured cells (cell lines):
-cells + virus = cytpathic (cell disease) effects (CPE) indicates growth
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Growth Viruses in the Lab:

3. Cell Line types (2)
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1. Primary cell line
2. Continuous cell line (CCL)
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Primary cell lines:
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cells with finite lifespan, cultured directly upon removal from animal.
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Continuous cell line (CCL):
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Immortalized cells-growing indefinitely in culture.
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Viral Multiplication steps:
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1.Attachment
2.Penetration
3.Uncoating
4.Biosynthesis
-includes replication, transcription, and translation
5.Maturation (assembly of body parts)
6.Release
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Types of Bacteriophage Multiplication:
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Lytic and Lysogentic cycles
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Lytic and Lysogenic cycles are present depending on virus type:
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-Both cycles found in lambda phage
-Only lytic cycle in T-even phages.
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Lytic Cycle:
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Ends with lysis and death of host cell
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what is an example of a type of phage that uses the lytic cycle:
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T-even phages attacking E. coli
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Lysogenic Cycle:
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Phage DNA becomes inserted i host cell genome as PROPHAGE
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what is an example of a phage that uses the lysogenic cycle?
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Lambda phage attacking E. coli
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how does Lambda phage transfer bacteria DNA to a different bacterium?:
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via TRANSDUCTION
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Animal Virus Multiplication:

Where do DNA VIRUSES multiply:
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multiply in the nucleus
-HOST enzymes transcribes viral DNA to give mRNA
-(EXCEPTION: in PROXVIRIDAE, viral enzyme does that!)
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Do ALL hosts enzymes of ANIMAL viruses transcribe viral DNA to give mRNA?
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NO!!! PROXVIRADAE- this viruses enzymes transcribes its own DNA to make mRNA.
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Animal Virus Multiplication:

In Retroviruses: (ex HIV, an RNA Virus)
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-Viral RNA is copied to make DNA by RNA-DEPENDENT DNA POLYMERASE, also called REVERSE TRANSCRIPTASE!
-DNA moves from cytoplasm to the nucleus and inserts into the host genome as PROVIRUS
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Animal Virus Multiplication:

RNA Viruses:
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Multiply in the CYTOPLASM
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What are the Enzymes involved in RNA replication?
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RNA-dependent RNA polymerase (RRP)
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Viruses and Cancer:

Why is viral cause of cancer difficult to establish/diagnose?
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Because:
1.Viruses
-are difficult to see
-many infect cells without causing cancer.
2.Cancers:
-are not contagious
-may not develop until long after viral infection is established.
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Viruses and Cancer:

Viruses that cause cancer are called oncogenic viruses:
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-many DNA viruses are oncogenic (ex-Papilloma virus)
-Oncogenic RNA viruses are found only in Retrovirade-and RNA Virus! (HIV)
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Viruses and Cancer

C. Cancer=uncontrolled cell proliferation cells become transformed and show what?
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1. Loss of contact inhibition
2. Chromosome changes
3. Tumor-specific transplantatioleus)n antigens-TSTA-(on cell surface)
4. T antigens (in nucleus)
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Latent vs. slow viral infections:

-Latent:
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-viruses remains for long periods without diseases
-infectious virus appears suddenly
-usually not fatal-does not kill-ex.
-cold sores by latent HSV-1
-Shingles by latent chickenpox virus
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Latent vs. slow viral infections:

slow/persistent
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-a disease process; occurs over long period of time
-infectious virus gradually builds up
-usually fatal-ex-
-AIDS dementia by HIV
-SSPE by measles virus
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Prions:

Prion disease is caused by what?
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an infectious protein called prions
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a Prion disease in sheep, cattle and humans
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-sheep: scrapies disease (Sc)
-cattle/cow: mad cow disease (also called bovine spongiform encephalopathy-BSE)
-Humans: Creutzfeld-Kakob disease and Kuru
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Viroids:

Viroid disease:
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-Is a plant disease-cause plant diseases
-caused by naked RNA
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Viroids:

Properties:
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-The RNA is 300-400 nucleotides long
-lik introns, the RNA does not code for a polypeptide
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Viroids:

Examples:
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-coconut cadang cadang viroid (CCCV) disease
-Potato spindle tuber viroid (PSTV) disease
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