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Quizlet > Cellular Genetics: Virus Quiz > Flashcards

Cellular Genetics: Virus Quiz Flashcards

1
Q

What is a virus?

A

An obligate, intracellular parasite made up of nucleic acid (DNA or RNA) and protein, sometimes surrounded by a membrane

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2
Q

Viruses lack the ability to acquire energy ____ .

A

Independently

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3
Q

How do viruses differ from each other?

A

In size, structure, genome type, host type, transmission

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4
Q

What are the 2 unifying characteristics of viruses?

A
  • All must make their own ribosomes that can be translated by the host (no viruses contain their own ribosomes)
  • All are obligate, intracellular parasites that can’t function or replicate outside of a cell
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5
Q

What is the main difference between viruses and bacteria?

A

Viruses do not grow and divide and do not have the metabolic properties of bacteria

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6
Q

What are two functions of the structural proteins found on viruses?

A
  1. Protection of genome
  2. Delivery of the genome
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7
Q

What does it mean that virus particles are metastable?

A
  • Must protect the genome (stable)
  • Must come apart on the infection (unstable)
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8
Q

What was the first ever virus to be discovered and what did it teach us?

A
  • TMV helped us understand that virus particles form spontaneously from subunits without any extra information
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9
Q

What is the implication of these self-assembling virus particles?

A
  • Particle is the most energetically favorable structure of the components
  • Gives the particle its inherent stability and is an important feature of virions.
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10
Q

What is a zoonotic virus?

A

One that is transmitted form an animal to human.

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11
Q

What is a vector?

A

An intermediate organism through which viruses are transmitted from one type of host to another.

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12
Q

What is a virome?

A

The entire population of viruses associated with the human body

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13
Q

What are the 3 virus particle types in the world of viruses?

A

Helical, icosahedral, and complex

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14
Q

Identify the 3 types of axis symmetry that govern the rules of icosahedral symmetry.

A
  • An axis of two-fold rotational symmetry through the center of each edge.
  • An axis of three-fold “ “ of each face.
  • An axis of five-fold “ “ of each corner (vertex).
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15
Q

What is the complex virus shape?

A

Bacteriophage

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16
Q

What is the helical virus shape?

A

Hollow, cylindrical capsid

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17
Q

What is the icosahedral virus shape?

A

Polyhedral capsid with 20 triangular facets

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18
Q

Distinguish among subunit, structural unit, capsid, nucleocapsid, and envelope.

A

Capsids are made up of repeated structural units, and structural units are made up of redundant subunits. The capsid is an effective barrier that when coated in a lipid envelope, together becomes the nucleocapsid. Viruses can either have or not have an envelope.

19
Q

What is a subunit? What is another name for it?

A
  • A single folded polypeptide chain
  • Also known as capsomere
20
Q

What is a structural unit?

A

One or more subunits from which capsids or nucleocapsids are built.

21
Q

What is a virion?

A

Infectious virus particle

22
Q

What is the capsid?

A

Protein shell surrounding genome

23
Q

What are some of the enzymes you can find in the capsid?

A
  • RNA-dependent RNA polymerase (enzyme that uses RNA as a template to produce RNA)
  • Reverse transcriptase (enzyme that uses RNA as a template for DNA synthesis)
  • Integrase (enzyme responsible for integrating viral DNA into host cell’s DNA)
  • Protease (enzyme that breaks down and modifies proteins)
24
Q

What does IRES stand for?

A

Internal ribosome entry site

25
Q

What does UTR stand for?

A

Untranslated region

26
Q

What is the nucleocapsid? When is it used?

A
  • Nucleic acid core and protein assembly
  • Used when is a discrete substructure
27
Q

What is the envelope?

A
  • Host cell derived lipid bi-layer
  • Outermost coating that surrounds the capsid and contains glycoproteins
28
Q

What does it mean for a cell to be susceptible?

A

A cell has a functional receptor for a given virus (may or may not to be able to support viral replication)

29
Q

What does it mean for a cell to be resistant?

A

A cell has no receptor (may or may not be competent to support viral replication)

30
Q

What does it mean for a cell to be permissive?

A

A cell has the capacity to replicate virus (may or may not be susceptible)

31
Q

What is required of a host cell to take up a virus particle AND replicate it?

A

Must be both susceptible AND permissive

32
Q

What are the basic steps of the replication cycle?

A
  1. Attachment and entry into the host cell
  2. Un-coating or release of genome
  3. Translation of viral proteins
  4. Replication of viral genome
  5. Assembly of new virus particles
  6. Release from cell
33
Q

What happens in attachment and entry?

A
  • Proteins on exterior of virus adhere to host cell membrane (absorption)
  • Attach to specific receptor molecules
34
Q

What are the two basic methods of uncoating?

A
  1. Fusion at the plasma membrane
  2. Within endosomes (endocytosis or engulfment)
35
Q

When does assembly begin?

A

When genome is copied AND viral proteins are synthesized (the capsid)

36
Q

What happens at assembly that only applies to enveloped viruses?

A

Only for enveloped viruses are there additional steps: acquisition of an envelope and maturation of virus particles

37
Q

Where do assembly happen?

A

Nucleus or cytoplasm

38
Q

How do enveloped and nonenveloped viruses exit the host cell?

A
  • Enveloped viruses exit through budding
  • Nonenveloped viruses exit through exocytosis, lysis (viral infected cell bursts and releases viruses) and death of cells
39
Q

Do animal viruses need receptors? Fungi and plant viruses?

A
  • Animal viruses need receptors
  • Fungi and plant viruses don’t. They enter cells by damage/openings.
40
Q

What are the receptors for influenza?

A

HA (hemagglutinin) binds to oligosaccharides

41
Q

What are the two receptors for HIV-1? Where are they found OR what is their function?

A
  • CD4 found on helper T-cells
  • CCR5 is necessary to trigger a fusion of the membrane
42
Q

What are the receptors for SARS CoV-2? What is their function?

A
  • ACE (angiotensin converting enzyme)
  • Plays a central role in controlling blood pressure through the regulation of fluids in the body
43
Q

What are (+) RNA viruses?

A

Genome can be directly translated to functional proteins by the ribosomes of the host cell

44
Q

What are (-) RNA viruses?

A
  • Require synthesis of an RNA strand complementary to the (+) RNA strand
  • Must carry an RNA replicase in virions to make complementary strand

Quizlet (3 decks)

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