L8 virus and virology

Question 1

How many groups in the Baltimore classification system

Answer 1

7

Question 2

List the four traits of viruses

Answer 2

• Virion
• Capsomere
• Assembly
• Capacity to evolve

Question 3

Decribe the four traits of virsuses

Answer 3

• Virion - extracellular infectious stage
• Capsomere - all have this cover that protexts nucleic acid in the virion
• Assembly - infected cells synthesise the virons component parts and then assembly into new virions. (in cytoplasm)
• Evolve - bc of its min composition of nucleic acids and protein capsomeres, virsus can change through evolution and alter nucleic acid in heritable ways.

Question 4

What are viruses

Answer 4

Obligate intracellular parasites

Question 5

What requires host cells to multiple with no machinery for protein synthesis and energy production?

Answer 5

Viruses

Question 6

Virus replication simple

Answer 6

Assembly of pre-made components

Question 7

Viruses are infectious particles minimally made up of what two things

Answer 7

Nucleic acids and proteins

Question 8

What is a capsid

Answer 8

The protein coat of capsomeres that surrounds the nucleic acids.

Question 9

What two classes are virions separated on?

Answer 9

Enveloped (has proteinaceous lipid bilayer) and naked (doesn not have lipid bilayer)

Question 10

Name Capsid shapes

Answer 10

• Spherical
• Helical
• Icosahedrons
• bacteriophages

Question 11

Spherical capsids are actually icosahedrons, which approximate the volume of a sphere yet are constructed from repeated subunits. Spherical capsids are somewhat rigid, whereas helical capsids can be rigid or flexible, depending on the virus.

Question 12

Spherical capsids are somewhat ____, whereas helical capsids can be ____ or ____, depending on the virus.

Answer 12

rigid
rigid or flexible

Question 13

Some bacteriophages combine icosahedral and helical elements, so that their heads that are full of nucleic acids are icosahedral but their tails are what?

Answer 13

helical assemblages of specialized tail proteins.

Question 14

what is a Nucleocapsid

Answer 14

In some viruses, the nucleic acid genome and the capsomeres are so intimately associated that their structure is termed a nucleocapsid.

Capsid together with enclosed nucleic acid

Question 15

Viral Structure

Answer 15

• Complete virus particle
• Infectious
• Composed of nucleic acid surrounded by protein coat, for protection
• Some viruses are enveloped

Question 16

Viral genomes

Answer 16

• DNA or RNA
• Sigle or double stranded
• Linear or circular
• Several separate segments
• Few thousand nucleotides to millions (giant viruses)

Question 17

Enveloped viruses may have what shapes of nucleocapsids

Answer 17

helical or icosahedral

Question 18

An example of a virus that lacks clearly defined capsids:

Answer 18

poxviruses

Question 19

Central dogma of molecular biology:

Answer 19

DNA —> RNA —> protein

Question 20

Which scheme is based on the central role of the translational machinery and the importance of viral mRNAs in programming viral protein synthesis?

Answer 20

Baltimore classification

mRNA is in the centre, with pathways to mRNA from DNA or RNA genomes.

Question 21

What is a quasispecies

Answer 21

Population structure of viruses with a large number of variant genomes (related by mutations).

Question 22

An example of a giant virus

Answer 22

mimivirus

Question 23

Cytopathic definition

Answer 23

Refers to structural changes in host cells that are caused by viral invasion.

Question 24

Animal cells in culture typically form ____ ____ in which cells introduced into a tissue culture flask attach to and spread out on the specially prepared plastic. As the cells undergo ____, the cell population increases in number until all the cells are touching one another without ________ (A); at this point, contact inhibition (touching other cells on all sides) prevents further population increase

Answer 24

• confluent carpets
• mitosis
• overlapping

Question 25

Virus-infected cells may display cytopathic effects that depend on the specific host cell and virus. For example:

Answer 25

many viruses cause infected cells to round up and detach from the tissue flask as they die.

Question 26

Virus-induced cytopathic effects (CPE) list

Answer 26

* Synctyia * Inclusion bodies * Transformed

Question 27

Describe virus-induced cytopathic effects (CPE)

Answer 27

* Synctyia: large multinucleate cells (Herpes) * Inclusion bodies: abnormal internal visible structuer and can form in cytoplasm/nucleus (Rabies) * Transformed: cancerous cells grow on top of each other instead of responding to contact inhibition as normal cells would.

Question 28

Virus naming schemes

Answer 28

* Disease they cause * Human body parts * Location found * Virion properties

Question 29

Viruses are cultured in animal and human cells in what type of lines

Answer 29

Continuous cell lines * Also cultured in whole animals, primary human cells and diploid cell strains

Question 30

Growth of virus in eggs

Answer 30

* Used to be propagated in chicken eggs * Today its used to grow influenza virus for vaccines * Egg placed in front of a light source to see and locate non-veined area of allantoic cavity below air sac * Virus injected into the cavity where it can replicate

Question 31

Growth of virus in laboratory animals

Answer 31

* Not common now * But mainly used as model system to study viral pathogenesis

Question 32

What is a Prion

Answer 32

Proteinaceous infectious particle

Question 33

Normal prion

Answer 33

Normal prion protein PrP (also known as PrP c ) encoded by PRNP gene is present in neurons as a normal cellular protein in tissue

Question 34

Prion function

Answer 34

Unknown but roles include tranport of copper and protection of neurons from injury and formation of neural synapse.

Question 35

Abnormal prions

Answer 35

* More than 30 abnormal forms -> Designated PrP(Sc) -> identified in people with familial disease * Cause spongiform encephalopathies: large vacuoles in brain * Major features include changes in memory, personality and behaviour; decline in intellectual function (dementia); abnormal movements, particularly difficulty with coordinating movements (ataxia)

Question 36

PrPc mutations that are associated with diseases including what change

Answer 36

single amino acid substitutions and truncated protein

Question 37

Formation of anormal PrP(C)

Answer 37

* The abnormal PrPSc can attach to PrPc and promote its transformation into PrPSc * Abnormal protein builds up in brain, forming clumps that destroy neurons * Loss of these cells creates microscopic sponge-like holes (vacuoles) in the brain, which leads to the signs and symptoms of the disease

Question 38

Prion diseases

Answer 38

* Scrapie (sheep) * Cronic wasting disease (deer) * Mad cow disease (– bovine spongiform encephalopathy) * Fatal familial insomnia (FFI)