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Genetics > Virology1 > Flashcards

Virology1 Flashcards

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Biology 101 flashcards
1
Q

briefly explain the history of virology

A
  • filterable agent infectivity for TMV & foot and mouth disease virus
  • first human virus described causes yellow fever
  • filterable viruses = Rinderpest, Vaccinia, Rabies, Cassava mosaic
  • Avian leukosis & poliomyelitis & chicken sarcomas shown to be caused by viruses
  • bacterial viruses discovered
  • spanish flu pandemic
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2
Q

what are 6 characteristics of viruses?

A
  • small & infectious (20nm - 300nm)
  • acellular pathogens
  • obligate intracellular parasites (host & cell-type specificity)
  • DNA/RNA genome (never both)
  • lack genes for products needed for reproduction
  • infect all types of cells
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3
Q

what is a virus’ genome surrounded by?

A

protein capsid (sometimes a phospholipid membrane w viral glycoproteins)

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4
Q

what are virions?

A

virus particles viruses reproduce through the exploitation of host-cell genomes

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5
Q

what are capsomers?

A
  • small structural unit that makes up a capsid
  • are an outer covering for the protection of the genetic material of a virus
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6
Q

what is a nucleocapsid?

A

capsid + genome

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7
Q

what are peplomers?

A

viral proteins that modify a virus envelope that was acquired from nuclear or plasma membrane of the infected host cell

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8
Q

what are the arguments for viruses being non-living? (4)

A
  • acellular
  • no cell nucleus, organelles or cytoplasm
  • can’t move
  • can’t reproduce
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9
Q

what are the arguments for classifying viruses as living? (4)

A
  • can only reproduce in living cells
  • obligate intracellular parasite
  • can evolve
  • genetic material
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10
Q

what type of microscope do you need to see viruses?

A

electron microscope

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11
Q

what’s the difference between the phylogeny of viruses and bacteria?

A

viruses → tangled
bacteria → natural

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12
Q

do viruses have ribosomes?

A

no

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13
Q

what are naked (nonenveloped) viruses ?

A

viruses that don’t have an envelope

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14
Q

what type of capsid structure is found in enveloped and nonenveloped viruses?

A

enveloped = helical
non enveloped & enveloped = icosahedral

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15
Q

which type of DNA virus isn’t icosahedral?

A

poxvirus

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16
Q

what are 3 characteristics of RNA viruses?

A
  • ss/self-duplicating RNA
  • high mutation rate
  • all plant viruses
17
Q

explain positive/negative sense of RNA

A

Positive sense (+sense) RNA = mRNA
Negative sense (-sense) RNA = Requires RNA polymerase to be converted to +sense RNA

18
Q

what are 3 characteristics of DNA viruses?

A
  • DNA dependent and replicate using DNA pol
  • dsDNA but sometimes can be ssDNA
  • most animal viruses are DNA viruses
19
Q

what are 3 types of viruses (ito what they infect)?

what type of genetic material does each type have

A
  • animal viruses → DNA or RNA
  • plant viruses → RNA
  • bacteriophage → DNA
20
Q

what are the different ways in which viruses can be transmitted?

A

direct contact, indirect contact with fomites or through a vector (mechanical or biological)

21
Q

what are zoonoses and reverse zoonoses?

A

zoonoses → transfer from animal to human
reverse zoonoses → transfer from human to animal

22
Q

what are the four viral structures?

+ describe them

A
  • helical (nucleic acid is spiral w capsomers helically around coil)
  • icosahedral (spherical shape w nucleic acid inside capsid, composed of 20 triangular faces)
  • spherical (round & some have spikes)
  • complex (don’t confirm into any category i.e. bacteriophages, poxvirus)
23
Q

what does a species, genus, subfamily, family and order refer to?

A
  • species → pop of viruses that share distinct pool of genes
  • genus → group of related viral species
  • subfamily → group of related viral genera
  • family → group of a related subfamily
  • order → group of family
24
Q

what are the 3 criteria for clasification of viruses?

+ brief explanation

A
  • morphology (size & shape, presence of envelope)
  • structural protein (contributes to molecular weight of virion)
  • nucleic acid properties (ds/ss, positive/negative sense sequence)
25
Q

what do segmented genomes do?

A

facilitate exchange of genome segments between different virus strains during coinfection of a single host cell (viral reassortment)

26
Q

what are the 2 major priorities of the virus life cycle?

A
  • make viral proteins
  • make copies of the viral genome
27
Q

what are the different polymerases and what do they do?

A
  • DdDp DNA dependent DNA pol = synthesises DNA from DNA (DNA → DNA)
  • DdRp DNA dependent RNA pol = synthesises RNA from DNA (DNA → RNA)
  • RdRp RNA dependent RNA pol = synthesises RNA from RNA (RNA → RNA)
  • RdDp RNA dependent DNA pol = synthesises DNA from DNA (RNA → DNA) (REVERSE TRANSCRIPTASE)
28
Q

what is the baltimore scheme?

A

a system that divides viruses into genome type and the mechanism of mRNA production

29
Q

what are class i viruses?

+ examples + type of enzyme (pol)

A

ds DNA
mRNA transcribed directly from DNA template

e.g. herpesvirus, adenovirus, most bacteriophages

dddp → copy + & - to produce dsDNA
ddrp → copy - into mrna → into proteins using host’s ribosomes

30
Q

what are class ii viruses?

+ examples

A

ssDNA
DNA coverted to double stranded before RNA is transcribed

e.g. canine parvovirus

dddp → copy + to produce dsDNA intermediate
ddrp → copy - strand of dsdna intermediate to produce + viral mRNA → translated into viral protein
dddp → copy - dsdna intermediate strand to produce ss(+) DNA viral genome

31
Q

what are class iii viruses?

A

dsRNA
mRNA transcribed from RNA genome

e.g. rotavirus (childhood gastroenteritis)

rdrp → copy both + & - to produce dsRNA genome
rdrp → copy - into + viral mRNA → translated into viral proteins

32
Q

what are class iv viruses?

+ examples

A

ssRNA (+)
genome functions as mRNA

e.g. coronavirus, pircornavirus (common cold), polio

rdrp → copies + to produce -ssRNA → rdrp copies - to produce +ssRNA
viral genome translated into viral protein

33
Q

class v viruses

+ examples

A

ssRNA (-)
mRNA transcribed from RNA genome

e.g. rabies or influenza

rdrp → copies - RNA to produce +ssRNA → rdrp copies +ssRNA to produce -ssRNA viral genome
rdrp → copies -RNA to form + viral mRNA → translated into viral proteins

34
Q

class vi viruses

+ examples

A

ssRNA viruses w reverse transcriptase
reverse trans → makes ssDNA from RNA genome → DNA incorporated into host genome → mRNA transcribed from incorporated DNA

e.g. HIV

reverse transcriptase possesses ribonuclease activity → degrade RNA strand of RNA-DNA hybride

reverse transcriptase → used as DNA pol to yield dsDNA → insert into host = provirus

35
Q

class vii viruses

+ examples

A

dsDNA w reverse transcriptase
DNA is replicated thru RNA intermediate (may serve directly as mRNA or template to make mRNA)

e.g. hepatitis B virus

36
Q

what is a provirus?

A

can remain latent indefinitely or cause expression of viral genes, leading to production of new viruses

37
Q
A

Genetics (14 decks)

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