Viruses (lecture 14) Flashcards

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1
Q

def

A

A virus is a very small, non-cellular parasite of cells.
Its genome, which is composed of either DNA or
RNA, is enclosed in a protein coat.

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2
Q

Are viruses living or nonliving?

A

Viruses belong to biology because they possess
genes, replicate, evolve, and are adapted to
particular hosts, biotic habitats, and ecological
niches. However…they are nonliving infectious
entities that can be said, at best, to lead a kind of
borrowed life.”

no metabolism

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3
Q

Virions

A

Virions are the virus delivery unit to new hosts

consist of the viral genome, the capsid, and often of
further accessory components

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4
Q

virion structure

A

envelope

matrix

genome

capsid:
-> protect the viral genome against inactivation.
recognize and attach to an appropriate host cell.

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5
Q

env virus?

advantage?

A

capsid containing viral genome without matrix and eveloping proteins

advantage:
resistance against environment
high variability&raquo_space; evolutionary advantage (host specificity?)

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6
Q

The Baltimore classification

A

type of genome,
type of transcription,
type of replication.

DNA, RNA and RT Viruses

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7
Q

Viral lifecycle

A
  1. Attachment of a virion to a cell
  2. Entry into the cell
  3. Transcription of virus genes into mRNAs
  4. Translation of virus mRNAs into virus proteins
  5. Genome replication
  6. Assembly of the virus proteins and genomes into
    virions
  7. Exit of the virions from the cell
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8
Q

Attachment of a virion to a cell

A

receptor involvement

viruses attach to specific structures on host cells -> cell specificity

e.g. HIV - CD4

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9
Q

diff between env and nakes virus entering a cell

A

naked: only by endocytosis

env: by endocytosis and membrane fusion
have fusion proteins with hydrophobic regions

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10
Q

bicistronic mRNA

A

bicistronic mRNA contains code for the translation of two genes. In the same vein, polycistronic RNA contains code for multiple genes, while monocistronic RNA contains code for only one gene. polycistronic RNA occurs most often in prokaryotes– an example is the lac operon

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11
Q

translation of viral mRNA

A

transcription of viral genome can be done by viral or host RNA Pols
(RdRp are always viral)
DdRp can be both

RdDp always viral (RTs)

traslation is always done by host cell
translation machinery

However, many
mRNAs are bi-cistronic

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12
Q

HSV-1

A

env

ds DNA

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13
Q

HIV

A

env

ss + RNA

retrovirus

genome for gag, pol, env, and auxiliary proteins

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14
Q

Viruses are used in research and clinics

A

Phage typing of bacteria

Source of enzymes

Pesticide

Anti-bacterial agents

Anti-cancer agents

Gene vectors for protein production

Gene vectors for treatment of genetic diseases

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