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UCLMS Yr 1 Mod 2: Infection and Defence > Viruses > Flashcards

Viruses Flashcards

1
Q

What is Koch’s postulates (To prove an agent causes a disease) (4)

A

Find Lesions
Isolate in pure culture
Inoculate pure culture to living organisms and cause disease
Recover again from lesion of host

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2
Q

What is the indirect demonstration of viruses (5)

A 
Grind animal/plant infected tissue into fluid suspension
Filter to retain bacteria
Inoculate filtrate
Watch for disease
Repeat the whole process to confirm
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3
Q

What is a pock

A

Damage due to smallpox virus

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4
Q

What are 3 uses of tissue culture to grow virus

A

Develop Vaccines
Identify new viruses
Virus Diagnosis

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5
Q

What type of symmetry are present in “spherical” caspids

A

Icosahedral

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6
Q

What are the main compositions of Infectious particle or virion (6)

A 
Genetic Material - DNA/RNA
Protein Coat - Capsid
Capsid and nucleic acid - nucleocapsid
Non-structural proteins - enzymes
Some viruses have an envelope - lipid bilayer and embedded glycoproteins
Virus symmetry based on capsomeres
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7
Q

What are Satellites (2)

A

Contin Nucleic Acid but lack genes for replication

Depend on coinfection with helper virus

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8
Q

What are Prions

A

No nucleic acid
Infectious proteins
Disease

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9
Q

What are the properties of Viruses (7)

A

Infect animals, plants, bacteria
Size - too small for light microscope
Classified by morphology, genome and replication
Extracellular infectious phase
Obligatory Intracellular regulation
Viral Genes subvert cell biosynthesis to replicate

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10
Q

What is the overview of the infectious cycle (6)

A 
Attachment and entry of the virion
Decoding of genome information
Translation of viral mRNA by host ribosomes
Genome replication
Viral Assembly 
Release of particles containing genome
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11
Q

What is the name of the viral attachment protein of influenza virus

A

Haemagglutinin

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12
Q

What is the viral receptor of influenza virus on the red cell

A

Sialic Acid

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13
Q

What is the name of the poliovirus receptor

A

PvR

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14
Q

What are 3 methods of viral entry

A

Fusion
Endocytosis and Fusion
Endocyosis

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15
Q

What does the viral genome contain

A

Information for instituting and completing an infectious cycle within a cell

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16
Q

What does expression and replication of the viral genome always depend on (2)

A

Depends on viral DNA or RNA

ALWAYS depends on viral mRNA

17
Q

Which genes are transcribed pre replication

A

Early Viral Genes

18
Q

What do Early Viral Genes do (3)

A

Regulate cell NA and protein synthesis
Regulate expression of the viral genome
Code for viral enzymes required for replication of viral nucleic acid

19
Q

When are late viral genes transcribed

A

post-replication

20
Q

What are the general features of the virus replication cycle (10)

A 
Attachment
Penetration
Uncoating
Transcription of Early mRNA
Translation of early proteins
Replication of viral DNA
Transcription of late mRNA
Translation of late proteins
Assembly virions
Release
21
Q

What are the 2 types of Viral RNA polarity

A

Positive - acts as mRNA

Negative - complementary to mRNA, when copied (by RNA dependent RNA polymerase) acts as mRNA

22
Q

What is the Baltimore classification

A

All viral genomes lead to mRNA

23
Q

What are the 7 types of Nucleic acid used by viruses in Baltimore classification

A 
dsDNA
ssDNA
dsRNA
ssRNA (+)
ssRNA (-)
ss retrovirus RNA (+)
Partially ds hepadnavirus DNA
24
Q

How does HIV enter the cell

A

gp120 (on HIV) binds to CD4 on the cell surface of the Th Cell
Co-receptor on the surface of the Th cell attracts gp120 by chemotaxis
gp41 (on HIV) inserts a fusion peptide into the target bilayer
A 6-helix bundle brings the two membranes closer, allowing the membranes to fuse

25
Q

What are the enzymes involved in the HIV replication cycle

A

Reverse Transcriptase
Integrase
Protease

26
Q

What is pro-viral DNA (2)

A

Retroviral DNA integrated into the host cell genome = provirus
Template for retroviral mRNA and genomic RNA

27
Q

Why do point mutations occur in RNA viruses

A

RNA polymerases have no proofreading

e.g. reverse transcriptase has no proofreading

28
Q

What is a quasi species

A

a mixture of molecular variants of an RNA virus

UCLMS Yr 1 Mod 2: Infection and Defence (7 decks)

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