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VMCB: Veterinary Virology > Lesson 1: Introduction to the study of viruses > Flashcards

Lesson 1: Introduction to the study of viruses Flashcards

1
Q

are the
smallest viruses (20nm)

A

picornavirus

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2
Q

are the largest viruses
(300nm)

A

poxviruses

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3
Q

Viruses cannot be seen by light microscope because of their small size except?

A

poxviruses

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4
Q

General description of Virus

A

• Filterable agents
• seen only by the aid of electron microscope
• No cellular organization and do not have organelles
• Composed of nucleic acid surrounded by a protein coat
• Contain only one type of nucleic acid, either DNA or RNA
• viable host
cells are required for replication
• Viruses are unaffected by antibiotics
• Viruses multiply by a complex process involving protein synthesis and nucleic
acid production

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5
Q

Three categories;

A

✓ DNA viruses
✓ RNA viruses
✓ Viruses that utilize both DNA
and RNA for replication

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6
Q

the viruses that infect bacteria

A

Bacteriophages or phages

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7
Q

an infectious extracellular virus particle consists of nucleic acid (DNA or
RNA) that is covered by a protein coat called CAPSID.

A

Virion

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8
Q

a shell of subunits of proteins called CAPSOMERE that encloses the
genome of vertebrate viruses

A

Capsid

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9
Q

a shell of subunits of proteins called CAPSOMERE that encloses the
genome of vertebrate viruses

A

Capsid

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10
Q

capsid functions

A

• offers protection for the nucleic acid against adverse conditions
• it facilitates attachment and entry of the virus into host cell
• it
possesses antigens used for virus identification in serological tests
• it
determines the symmetry of the virus

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11
Q

two types of capsid symmetry
described in viruses;

A

Icosahedral and helical symmetries

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12
Q

large viruses with large genome have
complicated symmetry which is neither icosahedral nor helical such as?

A

Poxviruses

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13
Q

used to refer to the combined nucleic acid and capsid
which can either be naked or covered with a membrane termed an envelope

A

nucleocapsid

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14
Q

The viral
genome also codes for important enzymes called _______________
required for viral replication but are not incorporated in the virion.

A

non-structural proteins

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15
Q

proteins that make up the subunit of capsid

A

structural proteins

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16
Q

generally assembled in the host cell prior to
incorporation of the viral nucleic acid

A

icosahedral capsid

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17
Q

formed by the insertion of protein units between each turn of
the nucleic acid helix, incorporating the RNA in the tubular package

A

Helical capsids

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18
Q

lipid bilayer and associated glycoproteins that cover a nucleocapsid

A

envelope

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19
Q

acquired when the nucleocapsid buds through a cellular membrane,
endoplasmic reticulum, the Golgi apparatus or the nuclear membrane

A

envelope

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20
Q

are usually susceptible to detergent and are rendered noninfectious following damage to the envelope

A

enveloped viruses

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21
Q

the proteins encoded by viral nucleic acid for binding to
receptors on host cells, membrane fusion, uncoating of the virion and destruction
of receptors on host cells

A

glycoproteins

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22
Q

are knob-like projections from the envelope formed from
the oligomers of glycoproteins.

A

peplomers/spikes

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23
Q

Peplomers/spikes are present in certain viruses including;

A

coronaviruses, retroviruses, orthomyxoviruses, rhabdoviruses and
paramyxoviruses

24
Q

a layer of protein present between the nucleocapsid and the
envelope in some enveloped viruses that provides additional rigidity to the virion

A

matrix protein

25
Q

Some viruses are named according to the type of disease they cause (creeping lesion) Examples;

A

poxviruses
herpesviruses

26
Q

viruses named based on acronyms of disease example

A

picornavirus and papovavirus

27
Q

Viruses are also named based on morphology as revealed by electron microscopy example;

A

coronavirus, togavirus, rhabdovirus, and calicivirus

28
Q

viruses are named after individual discoverer

A

Epstein-bar viruses

29
Q

developed and expanded the universal scheme in which characteristics of
virions are used to assign them to five hierarchical levels (order, family,
subfamily, genus and species).

A

International Committee on Taxonomy of Viruses (ICTV) 1973

30
Q

The hierarchical levels are denoted with the following suffixes:

A

Order: -virale
Family: -viridae
Genus: virus
Species: virus

31
Q

Four orders containing viruses of animals are so far recognized:

A

• mononegavirale
• herpesvirales
• picornavirales
• nidovirales

32
Q

are infectious particles, which can transmit a disease, composed mainly
of a protein without any detectable nucleic acid.

A

Prions

33
Q

___________ causative agents of slow viral infections such as ___________

A

Prions
Subacute spongiform encelophathy

34
Q

After long incubation period of years, Prions produce
a progressive disease that causes damage to the central nervous system,
leading to

A

subacute spongiform encephalopathy

35
Q

Susceptibility to Physical and Chemical Agents

A

• Disinfectants
• Temperature
• pH
• lipid solvents
• radiations

36
Q

initial stage of virus replication
whereby the infecting virus loses its physical identity and most or all of its infectivity

A

eclipse phase

37
Q

stage as new viral particles are formed and released from the cell
wherein the number of viral particles increases exponentially.

A

productive stage

38
Q

Steps in Virus Replication

A

Attachment
Entry
Uncoating
Biosynthesis or Replication of nucleic acid
Maturation/Assembly of virus

39
Q

enveloped viruses enter the cell by an alternate method called
___________, in which the viral envelope fuses with the plasma
membrane and releases the capsid into the cell cytoplasm.

A

Fusion

40
Q

naked viruses or non-enveloped viruses undergo a
receptor-based endocytosis also known?

A

viropexis

41
Q

process of separation of viral nucleic acid from its protein
core for transcription to take place

A

uncoating

42
Q

in certain viruses, transcription may
proceed without complete release of the viral genome

A

reovirus

43
Q

Replication of DNA viruses

A

DNA viruses replicate their DNA in the
nucleus of the host cell by using viral enzymes.

44
Q

Replication of RNA viruses

A

RNA viruses replicate in the cytoplasm
except orthomyxoviruses and Borna disease virus which require host DNA
transcription inside the nucleus, paramyxoviruses which have a non-obligatory
nuclear phase of replication and retroviruses which replicate via a DNA
intermediate (provirus)

45
Q

Abnormal replicative cycles may occur in four ways:

A

incomplete viruses
pseudovirions
abortive infections
defective viruses

46
Q

Due to defect during assembly of viral components, some of
the daughter virions that are produced may not be infective

A

incomplete viruses

47
Q

viruses that occasionally enclose host cell
nucleic acid instead of viral nucleic acid, therefore, are non infective and lack the
capability to replicate.

A

pseudovirions

48
Q

type of infection, the virus components may be
synthesized but the maturation is defective maybe due to infection of the wrong host
cells by the virus.

A

abortive infections

49
Q

are viruses that produce fully mature virions only in the
presence of helper viruses which supplement the genetic deficiency in the defective
viruses

A

Defective viruses

50
Q

Example of defective virus

A

Hepatitis D virus, replicate only in the presence of Hepatitis B virus (helper virus)

51
Q

Spontaneous and random errors in the copying of viral nucleic acid

A

mutations

52
Q

can occur during the replication of viruses. It is the most important
mechanism by which a virus can be genetically modified which results in production
of new viral strains showing properties different from parental or wild-type virus such
as inactivation of viruses, altered antigenicity and pathogenicity of the virus, and
induce drug resistance in viruses

A

mutations

53
Q

resulting from single nucleotide substitutions, are the most common type
of mutation

A

point of mutations

54
Q

a new area of antiviral research wherein those RNA viruses with
inherently high mutation rates are administered with mutagenic agents to drive viral
extinction through violation of the error threshold and error catastrophe.

A

lethal mutagenesis

55
Q

is the extinction of an organism as a result of excessive
mutations

A

error catastrophe

VMCB: Veterinary Virology (7 decks)

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