I&d How Viruses Multiply

Front 1

Do viruses have any metabolic activity of their own?

Back 1

No

Front 2

What must a virus do in order to replicate itself? How does it achieve this?

Back 2

Infect the cell - The virus takes over the biochemical machinery of the host cell and redirects it to manufacture viral components

Front 3

What is the name for the special proteins that allow viruses to bind to a receptor on the cell membrane?

Back 3

Attachment proteins

Front 4

What are the two ways for a virus to enter the cell?

Back 4

Fusion (enveloped viruses)
Endocytosis (enveloped & non-enveloped viruses)

Front 5

What is 'uncoating'?

Back 5

Release of the virus' genome from its protective protein coat - it is then 'accessible' so that viral genes can be expressed.

Front 6

What are the five stages of viral replication?

Back 6

Attachment, penetration, uncoating, expression and replication of viral genomes, viral assembly and release

Front 7

How is a non-enveloped virus assembled and released?

Back 7

Assembly of capsid and viral genome occurs in nucleus/cytoplasm

DISINTEGRATION of dying cell needed for release of virus

Front 8

How is an enveloped virus assembled and released?

Back 8

Nucleocapsid attaches to viral proteins inserted into the cell membrane, new virion 'buds' from the still viable cell

Front 9

What is a 'nucleocapsid'?

Back 9

Genome and the protein coat of a virus.

132941110 - Thurs, intermodular week (:

Front 10

What is a 'capsid'?

Back 10

The protein coat of a virus

Front 11

List the process involved when a dsDNA virus attacks a cell (4)

Back 11

1. Early genes transcribed (take over cell's machinery but maintains cell's viability)
2. DNA replication (DNA genome synthesised)
3. Later transcription and translation (produce late mRNAs which code for structural proteins)
4. Productive infection (Release of progeny virus from infected (permissive) cell)

Front 12

What is the name for a cell that has been infected?

Back 12

A 'permissive' cell

Front 13

What replicative enzyme is used in a dsDNA virus?

Back 13

DNA-dependent DNA polymerase

Front 14

What type of virus encodes its own DNA polymerase?

Back 14

Herpesvirus

Front 15

What is the name for the type of virus that hijacks the cell's DNA polymerase?

Back 15

Papillomavirus

Front 16

What is the Baltimore Classification?

Back 16

A classification system for viruses according to their type of genome and their method of replication.

Front 17

What is the positive sense strand?

Back 17

It serves as a template for protein synthesis.

Front 18

What is the negative sense strand?

Back 18

It serves as a template for the transcription of viral complementary RNA.

Front 19

What is a 'latent' virus?

Back 19

When infected by a virus in the latent stage, the cell is transiently non-permissive - it does not produce the infectious virus

The viral genome is maintained with few genes expressed - when the virus reactivates, full replication occurs and infectious progeny virus is produced

Front 20

Comment on the genetic diversity of viruses. (3)

Back 20

Greater genetic diversity than any other group of organisms - produced by:
point mutation, reassortment, recombination

Front 21

What is a retrovirus?

Back 21

An RNA virus that is replicated in a host cell via the enzyme reverse transcriptase to produce DNA from its RNA genome. The DNA is then incorporated into the host's genome by an integrase enzyme. The virus thereafter replicates as part of the host cell's DNA. Retroviruses are enveloped viruses that belong to the viral family Retroviridae.

Front 22

What type of virus is HIV?

Back 22

A retrovirus

Front 23

What is the HIV replication cycle? (9)

Back 23

Attachment via CD4 and a co-receptor
Uncoating
Reverse Transcription
Linear dsDNA in viral pre-integration complex
Integration
Transcription
Translation
Core particle assembly
Final assembly and budding

Front 24

What is CD4?

Back 24

(Cluster of differentiation 4) is a co-receptor that assists the T cell receptor (TCR) in activating its T cell following an interaction with an antigen-presenting cell

Front 25

What is Haemagglutinin?

Back 25

A viral attachment protein.

Front 26

The viral attachment (VA) protein normally binds to a cellular receptor. What receptor is this?

Back 26

Sialic acid

Front 27

HIV Envelope Protein Offers Key
to Cell Entry

Back 27

Viral envelope protein
is a trimer (think: monomer, dimer)
– 3 gp120 subunits
bind cell receptors
– 3 gp41 subunits
cause fusion

Coreceptor binding—the trigger leading
to changes in gp41 & membrane fusion

Front 28

Back 28

.

Front 29

What is integrase?

Back 29

An enzyme produced by a retrovirus (such as HIV) that enables its genetic material to be integrated into the DNA of the infected cell.

Front 30

What is proviral DNA?

Back 30

Retroviral DNA integrated into the
host cell genome = provirus.

Template for retroviral mRNA &
genomic RNA

Front 31

RNA viruses often much higher error rate because...

Back 31

They have no proof reading system

Front 32

What is a quasispecies?

Back 32

A normal virus, but with a mutation (very common due to lack of proof-reading)

Front 33

What is a positive sense strand?

Back 33

One which acts as mRNA

Front 34

What is a negative sense strand?

Back 34

One which is complimentary to mRNA - when it is copied it acts as mRNA

Front 35

What does haemagglutin (causes RBCs to agglutinate) bind to?

Back 35

Sialic acid

Front 36

Define 'Agglutination'

Back 36

The clumping of particles/cells

Front 37

What is reassortment? (Wrt contributing to bacterial genetic diversity)

Back 37

Exchange of entire RNA molecule within a virus (there are lots of segmented parts of the genome in some viruses)

Front 38

What is recombination? (Wrt contributing to bacterial genetic diversity)

Back 38

Exchange of part of an RNA genome (remember that the genome is segmented sometimes)