virology test 1

Martinus Beijerinck coined the name “virus” after his discovery that a filterable infectious agent infected what type of plants?

tobacco

virus is from the latin for what?

poison

what kind of coat does a virus have?

protein coat

are viruses able to multiply by themselves?

no

where is a virus only able to multiply?

in the living cells of a host

what kind of molecule does a virus consist of?

nucleic acid molecule

what are the four properties of all viruses?

small size, intracellular parasites, two basic components, viral genome

what does the small size property help viruses with?

allows them to be filterable infectious agents

what does it mean for a virus to be obligate, intracellular parasites?

they have to live in cells

what are the two basic components of a virus?

nucleic acid genome and protein coat

what are the two viral genomes?

DNA and RNA

can viruses pass through filters that trap most bacteria?

yes

what is used to visualize viruses?

electron microscope

what shape is this?

icosahedral

most viruses are how many nm in size?

20-300

what virus is this

herpes simplex virus

what virus is this

influenza virus

what virus is this

ebola virus

viruses are dependent on cells for what reasons?

supply energy and means of DNA and protein synthesis

what cell parts are viruses dependent on?

mitochondria, ribosomes, cellular enzymes

another word for a virus protein coat?

capsid

what are the two ways viruses are classified?

DNA and RNA

what are the three types of DNA genomes

single stranded, double stranded, circular

what are the three types of RNA genomes

pos or neg, segmented, double stranded segmented

what are the 6 DNA viruses?

parvoviridae, papovaviridae, poxviridae, adenoviridae, hepadnaviridae, herpesviridae

viruses must ____ required processes not provided by the cell

encode

do viruses undergo mitosis or meiosis?

no

do viruses undergo binary fission?

no

are viruses susceptible to antibiotics?

no

why cant viruses be cultured on artificial media, such as agar plates?

they require cells to grow

what are the two basic types of viral shapes?

icosahedral capsid and helical capsid

geometric shape composed of 20 identical equilateral triangles

icosahedron

what do all helical viruses have?

an RNA genome and an envelope

do helical viruses have any DNA genomes?

no

do all viruses have envelopes?

no

what are virus envelopes derived from?

cell plasma membrane

does the viral envelope have to be intact to be infectious?

yes

the viral envelope is environmentally labile, what does this mean?

sensitive to environmental and other factors, acid, detergents, GI tract

how are viruses with a viral envelope spread?

person-to-person contact

what are some examples of person-to-person contact that viruses can spread

respiratory droplets, secretions, blood, transplants, injections

envelope antigens are targets for what

immune responses and vaccine components

two examples of enveloped viruses with helical capsid symmetry

measles and influenza

two examples of non enveloped viruses with icosahedral symmetry

adenovirus and rotavirus

do all helical viruses have an envelope?

yes

do all icosahedral viruses have an envelope?

no

what kind of symmetry do poxviruses have?

complex

what is virus classification (taxonomy) based on?

physical and chemical properties

what are some examples of physical and chemical properties of viruses

size, morphology, DNA or RNA genome, replication strategies

what are some characteristics that prove viruses are alive?

can reproduce, can adapt and evolve

what are some characteristics that prove viruses are not alive?

not composed of cells, cannot live independently

what are some characteristics that prove viruses may be alive?

can grow in number but not in size, require energy but dependent on cell

viruses have limited capacity to synthesize all of the products needed to replicate due to what characteristic?

smaller genome

viral replication largely depends on using what?

cellular biosynthesis machinery

what unwinds the parental double helix?

helicases

what does the single strand binding protein stabilize?

the unwound parental DNA

in what direction is the leading strand synthesized?

5’ to 3’

what synthesizes the unwound strand in DNA replication?

DNA polymerase

what synthesizes a short RNA primer on the lagging strand?

primase