General-Structure-Etc. (Ex1)

Question 1

What are viruses?
General Features (6)

Answer 1

• non-living entities
• contain nucleic acid genome surrounded by protein coat
• do not possess organelles
• cannot make energy or proteins by themselves
• are obligate intracellular parasites
• cannot multiply by division

Question 2

What is a virion?

Answer 2

a complete virus particle that consists of an RNA/DNA core with a protein coat

Question 3

Edward Jenner

Answer 3

• invented vaccinations

- cowpox matter to prevent small pox

Question 4

Charles Chamberland

Answer 4

• invented the Chamberland filter

- pores smaller than bacteria

Question 5

Louis Pasteur

Answer 5

• created Rabies vaccine

- infected rabbit brain material into patients

Question 6

Martinus Beijerinck

Answer 6

• called infectious substance a virus

- Tobacco Mosaic virus

Question 7

Friedrich Loeffler and Paul Frosch

Answer 7

• discovered cause of foot and mouth disease

Question 8

Walter Reed

Answer 8

• conqueror of yellow fever

- spread by mosquitoes

Question 9

Peyton Rous

Answer 9

• isolated first tumor-causing animal virus

- Rous sarcoma virus

Question 10

Ernst Ruska and Max Knoll

Answer 10

invented electron microscope

Question 11

Woodruff, Goodpasture, and Burnet

Answer 11

• propagated fowlpoxvirus in embryonated hens eggs

Question 12

Which are the smallest viruses?

Answer 12

• Porcine circovirus type 1

- Parvoviruses

Question 13

Which are the largest viruses?

Answer 13

• Pandoravirus

- Poxvirus

Question 14

What is a capsid?

Answer 14

the protein shell of a virus that encases the viral nucleic acid or genome
- made up of capsomeres

Question 15

What is the Triangulation number and what is the equation to calculate it?

Answer 15

• describes the relation between the number of pentagons and hexagons of the icosahedron
• the larger the number, the more hexagons relative to pentagons
• T=(h^2 + h)(k + k^2)

Question 16

What are the functions of the viral envelope?

Answer 16

• facilitates entry into host cells

- helps virus adapt fast and evade host immune system

Question 17

Describe virus envelope glycoproteins

Answer 17

• anchored in the lipid bilayer by hydrophobic bonds
• transmembrane proteins with large external domain and small cytoplasmic domain
• external (antigens), channel, fusion

Question 18

Features of Electron Microscopy

Answer 18

• Biological materials need to be stained
• Requires negative staining with electron dense material
• not very detailed

Question 19

Features of Cryo-Electron Microscopy

Answer 19

• biological specimens in their native environment

Question 20

What are the functions of the viral capsid?

Answer 20

• structural symmetry of virus particle
• protects viral nucleic acid
• facilitates attachment to receptors on host cell
• transport of viral genome to specific site
• determines antigenicity of virus

Question 21

Describe the virus envelope matrix proteins

Answer 21

• link the internal nucleocapsid to the envelope
• crucial role in virus assembly
• stabilization of lipid envelope
• recognition site of nucleocapsid at the plasma membrane and mediates encapsidation of nucleoprotein cores into membrane envelope

Question 22

Positive Sense RNA Virus

Answer 22

• has an infectious genome

- similar to mRNA and can be immediately translated by host cell

Question 23

Negative Sense RNA Virus

Answer 23

• has non-infectious genome

- complementary to mRNA and must be converted to positive sense before translation

Question 24

What happens in each of the point mutations?

silent, nonsense, missense

Answer 24

Silent: codes for the same amino acid
Nonsense: codes for a stop codon
Missense: codes for a different amino acid

Question 25

What happens in recombination?

Answer 25

exchange of nucleotide sequences between different, but closely related, viruses during replication - involves a single gene segment

Question 26

What happens in reassortment?

Answer 26

coinfection with two different strains - segments mixed up in host - forms reassortment progeny - only in viruses with multiple gene segments

Question 27

What are lysins?

Answer 27

hydrolytic enzymes produced by bacteriophages to cleave the host's cell walls

Question 28

What is retroviral integrase?

Answer 28

enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cells

Question 29

What is reverse transcriptase?

Answer 29

enzyme used to generate complementary DNA from an RNA template

Question 30

What are neuraminidases?

Answer 30

enzymes that cleave glycosidic bonds which allows release of viruses from host cell

Question 31

What are Defective Interfering Particles?

Answer 31

when the defective virus cannot replicate, but it can interfere with other congeneric mature virions entering the cells

Question 32

What is a pseudovirion?

Answer 32

- contains non-viral genome within the viral capsid | - looks ordinary but does not replicate