viruses Flashcards

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1
Q

what are viruses

A

They are simple, acellular entities of one or more molecules of DNA or RNA not both and are enclosed in a coat of protein, lipids or carbohyratesand can only reproduce in living cells- obligate intracellular parasites

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2
Q

examples of airborne disease

A

chickenpox, shingles, germen measles (rubella) and influenze

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3
Q

examples of arthropod borne disease

A

yellow fever arbovirus

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4
Q

examples of direct contact diseases

A

AIDS, cold sires, common cold, genital herpes, rabies and hepatitis

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5
Q

examples of food-borne diseases

A

polio and infectious hepatitis

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6
Q

examples of other virueses

A

warts, verucas, HPV

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7
Q

what is the geonme of a viruse

A

RNA or DNA, double or single stranded, segmeted or non-segmented

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8
Q

what is the compoisition of the envelope

A

lipids from host cell membrane, proteins and glycoproteins

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9
Q

what is the function of the enevlope

A

camoflage and recognition and attachment to host cell

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10
Q

what are capsids

A

the proteins forming the virus shell. they are rings

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11
Q

what is verial shape

A

helical or isometric (cubic). the number of protein molecules in the virus are large but rarely more than one

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12
Q

what are icosahedral capsids

A

form ring shape units called capsomeres- 5 or 6 protomers

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13
Q

explain the classification of viruses

A

host range= very specific, but can jump between species through mutations
envoloped or non
type of nucleic acid= single or double
shape= different shapes

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14
Q

what is the size of viral shape

A

10-500nm and 1000 microletersin a naometre

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15
Q

what is icosahedral

A

polyhedron with 20 triangular faces

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16
Q

what is helical

A

hollow rigid or flexible cylinders

17
Q

what is envoloped

A

outer membranous layer surrounding either of the 2 above shapes

18
Q

what is complex

A

they have a head (icosahedral) and a tail (helical) and other parts

19
Q

what happens to viruses if they are left for long periods

A

they crystalise

20
Q

explain intracellular and extracellular

A

extracellular- outside of cell- they dont breath or have any activity
intra- inside the cell
attaches to chromosome and then becomes alive

21
Q

how did viruses used to be cultivated

A

old way was using fertilised chicken eggs 6-8 days after fertilisation . Different viruses like different parts of the embryo and when it grows it forms pocks

22
Q

what are used more now

A

use animal and plant tissue cultures- monolayer of cells or protoplasts,causing plques or necrotic lesions or abnormalaties called cytopathic effects

23
Q

why are bacterial and fungal antibiotics needed on cultures

A

the media we use for tissue cuultures are rich and stop growth and allow viruses to grow we need bacterial and fungal antibiotics

24
Q

what are bacteriophagus cultivated in

A

broth or agar cultures - results in clearing of broth or plaques on agar plates

25
Q

what are the signs of viral propagation

A

death of an embryo
plocks on membranes
plaque- disease that affects humans and other mammels
necrotic lesions that lead to discolouration of skin

26
Q

what are the techniques for isolating viruses

A

centrifugation, precipitation, denaturation and enzymatic denaturation

27
Q

types of centrifugation

A

differential or gradient

28
Q

what is precipitation

A

using ammonium sulphate followed by centrifugation

29
Q

what is denaturation

A

using heat, pH changes or solvants and may inactivate the viruses

30
Q

what is enzymatic denaturation

A

looks into cell components leaving viruses unharmed

31
Q

what is LD50

A

lethal dose- amount of ingested substance that kills 50% of a test sample

32
Q

what is ID50

A

Infected dose- inoculum required to infect 50% of a population

33
Q

tools used to study viral replication and mechanisms can be carried through…

A

enumerationand measuring infectious units

34
Q

what are PFUs

A

plaque/ pock forming units