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Virology > Viral Genetics And Cultivation > Flashcards

Viral Genetics And Cultivation Flashcards

1
Q

What is viral Genetics??

A

Knowledge of heritable information in virus which include viral genome structure, replication and genetic change

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2
Q

Viruses are continously changing as a result of Genetic selection

True /false

A

True

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3
Q

What are the methods virus use to change their structure??

A

Mutations
Recombination

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4
Q

What is genetic mutation??

A

Change in dna sequence of an organism

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5
Q

What factors facilitate the survival of a progeny that has been genetically mutated??

A

Early occurrence of mutation in the course of infection.

Provision of selective advantage by mutation.

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6
Q

What are the four types of viral genetic recombination??

A

Intramolecular recombination
Reassortment
Reactivation
Marker rescue or cross reactivation

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7
Q

Intramolecular recombination is commonly seen in which kind of viruses??

A

DsDNA viruses and retrovirus

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8
Q

Intramolecular recombination is rarely seen in which virus?

A

Poliomyelitis virus

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9
Q

Viral Reassortment occurs only in what kind of viruses??

A

Segmented viruses

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10
Q

What are the examples of segmented viral families?

A

Arenaviridae
Bunyaviridae
Birnaviridae
Reoviridae
Influenza A and B

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11
Q

How many segments does arenaviridae have??

A

2

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12
Q

How many segments does Bunyaviridae have?

A

3

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13
Q

How many segments does Birnaviridae have?

A

2

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14
Q

How many segments does influenza A and B virus have?

A

8

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15
Q

How many segments does Reoviridae have?

A

10-12

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16
Q

What is viral Reassortment??

A

Exchange of segments occurring btw two viruses resulting in the synthesis of various stable viruses

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17
Q

Explain the mechanism of viral reactivation?

A

Two viruses of the same strain infect the host, both these viruses having lethal mutations on different genes.

Coinfection results into viable recombinants.

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18
Q

What are the examples of viruses that undergo viral reactivation?

A

Pox virus
Orthomyxoviruses
Reovirus

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19
Q

What are the mechanism of cross reactivation or Marker Rescue??

A

Two viruses, one infectious and the other inactivated enter a host cell simultaneously

By the process of gene transfer, they produce a recombinant that has active gene from both viruses

The recombinant now continues to produce its yield

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20
Q

Cross Reactivation or Marker Rescue occurs btw
Infectious + non infectious
Two infectious
Two noninfectious
True/false

A

True

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21
Q

What is complementation??

A

It’s a phenomenon in which the proteins and enzymes produce by two viruses complement the action of each other to have increased yield of one or both viruses

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22
Q

Complementation can occur btw unrelated viruses
True/false

A

True

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23
Q

What is phenotypic mixing?

A

This occurs when a progeny has the phenotypic character of both the parents and the genome of the true parent. Occurs in envelopes of the enveloped virus and capsid of naked virus.

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24
Q

What is interference??

A

It is the inhibition of the growth of a virus in the host cell when it is simultaneously infected by another virus

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25
Q

What mediates interference??

A

Interferon

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26
Q

What are the importance of viral cultivation?

A

Studying the properties and behaviour of different viruses

Developing vaccines and treatment for viral infections

27
Q

What is virus cultivation??

A

This is the process of growing and propagating virus in a laboratory

28
Q

Describe the mechanism of viral cultivation

A

It’s done by infecting a host cell culture with a virus of choice.

Host cell can be animal, plant or bacteria cell

The virus replicates and forms more virus and they are harvested and used for experimentation

29
Q

Where are the methods of viral cultivation??

A

Animal inoculation,
Embryonated egg,
Cell culture.

30
Q

Purpose of virus cultivation??

A

Scientific research,
Development of vacancies,
Treatment of viral infection,
Understanding virus behaviour.

31
Q

List the specimens used for virus cultivation

A

Blood
Tissue
Saliva/Sputum
Urine
Stool
Swab
Fluids

32
Q

Where are swap samples gotten from?

A

Body surface

33
Q

Example of viruses cultured on blood samples?

A

Hiv, hepatitis b and c, dengue virus

34
Q

Examples of viruses cultured in Saliva samples

A

Influenza, respiratory syncitial virus(rsv)

35
Q

Examples of viruses cultured in urine sample?

A

Zika virus

36
Q

Examples of viruses cultured in Stool samples?

A

Norovirus, rotavirus

37
Q

Examples of viruses cultured in Swab samples?

A

Herpes simplex, varicella zoster virus

38
Q

Lab mice of age less than 48hours is animal of choice for the cultivation of which virus?

A

Toga virus, coxsackie virus

39
Q

What is the method of animal inoculation??

A

Suckling lab mice/ any other animal is used for inoculation of a virus sample

After inoculation, animals are observed for symptoms of disease till death

And finally virus is isolated from tissue of animal

40
Q

What’s the time frame for the egg embryo used for Embryonated egg culture?

A

7-12 days

41
Q

Which part of the egg is pox virus cultivated in?

A

Choriallantoic membrane

42
Q

Which viruses are cultivated in the allantoic cavity??

A

Influenza, mumps, yellow fever, rabies

43
Q

Which virus is cultivated in the yolk sac?

A

Herpes virus.

44
Q

Why is allantoic cavity culture done??

A

To prepare for vaccines and to obtain large amounts of virus load

45
Q

When influenza virus is cultured in amniotic sac, what’s the essence??

A

For isolation of virus from clinical sample

46
Q

Describe the mechanism of Embryonated egg culture?

A

An egg is incubated for embryo dev for up to 7-12 days,

A virus sample is introduced into the egg with paraffin wax to seal the opening,

Then the egg is incubated for a sufficient time.

47
Q

What are pocks?

A

The grey white lesions growing in the choriallantoic membrane.

Number of pocks represents the number of viruses inoculated in the specimen.

48
Q

What are the three types of cell culture technique?

A

Organ culture,
Explant culture,
Cell line culture.

49
Q

Describe the organ culture technique

A

Used to study the growth and replication of virus using a specific organ,

Organ/ tissue is cut into small pieces and put in a culture dish containing a nutrient rich medium,

Virus is inoculated into the organ and culture is incubated under appropriate conditions.

50
Q

What is Explant culture?

A

It’s a culture used to study the growth and replication of cells and tissue outside of the body.

51
Q

What are the advantages of Explant culture?

A

Ability to study virus replication in a more physiologically relevant environment.

52
Q

Mechanism of Explant culture.

A

Same with organ culture

53
Q

What are the types of cell line culture?

A

Primary,
Semi continuous,
Continuous.

54
Q

Describe the mechanism of cell line culture?

A

At first, growth media is prepared by maintaining stable salt conc, all essential amino acids, buffer agents, glucose, etc.

A tissue fragment is obtained and trypsionised to dissociate cell.

Dissociated cell is washed and suspended in culture media in a periplate and incubated for a sufficient time.

On incubation, cells divide and spread to form a confluent mono layer of cells which is now used for virus culture.

55
Q

About primary cell line??

A

They are normal cells gotten from human and animal.

They divide by mitosis to form confluent mono layer.

Used for isolation of virus and preparation of vaccines.

Cannot be maintained in serial sub culture.

56
Q

Examples of primary cell line include??

A

Monkey kidney cell line
Human amnion cell line

57
Q

About semi continuous cell line?

A
  1. They are fibroblastic cells.
  2. They are diploid cells containing same number of chromosomes as the parent cell.
  3. Can be sub cultured for limited generation.
  4. Susceptible for a wide range of culture and used for vaccine production.
  5. There is rapid cell division and undergo senescence after 50 serial sub culture.
58
Q

Where are fibroblastic cells obtained from??

A

Embryo tissue

59
Q

Examples of semi continuous cell line

A

Rhesus embryo cell,
Human embryonic lung strain.

60
Q

About continuous cell line

A
  1. Cells of a single type capable of infinite growth.
  2. Usually derived from cancerous tissues.
  3. They grow faster and are haploid.
  4. Used for viral culture but not vaccine preparation.
  5. Maintained by serial sub culture or deep freezing at - 70°C.
61
Q

Examples of continuous cell line??

A

HeLa
Hep-2
Vero

62
Q

Where is HeLa cell line obtained from?

A

Cervical cancer

63
Q

Where is Hep-2 obtained from?

A

Human epithelioma of larynx cell line

64
Q

Where is vero obtained from?

A

Vervet monkey kidney cell line

Virology (4 decks)

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