Definitions (Ppt I)

Question 1

Progressive hypothesis

Answer 1

Viruses arisen from mobile genetic elements that could move between cells

Question 2

Regressive or reduction hypothesis

Answer 2

Evolved from free-living ancestors that adapted a parasitic replication strategy

Remnants of cellular organisms

Question 3

Virus first hypothesis

Answer 3

Viruses predate or coexist with their current host

Question 4

3 reasons why viruses are beneficial

Answer 4

Biodiversity, residual immunity to subsequent infection, eliminate harmful bacteria

Question 5

All viruses are obligate _______ organisms

Answer 5

Intracellular

Question 6

Nucleocapsid parts

Answer 6

Capsid and nucleic acid

(Some have an envelope)

Question 7

Virus

Answer 7

General description

Question 8

Virion

Answer 8

Mature infectious particle

Question 9

Viroid

Answer 9

Plant virus

Question 10

Are empty capsids infectious?

Answer 10

No

Question 11

Common viral shapes

Answer 11

Icosahedral, helical, complex symmetry

Question 12

Which shape is the most common

Answer 12

Icosahedral

Question 13

Grouping of viruses are based on…

Answer 13

Shape & size of virus, shape & size of nucleic acid, type of nucleic acid, host, vector, location of viral replication, + or - sense, enveloped or non enveloped, capsid symmetry

Question 14

Families end in

Answer 14

-viridae

Question 15

Genus end in

Answer 15

-virus

Question 16

Where are proteins found in viruses

Answer 16

Lipid envelope, capsids, tegument

Question 17

4 stages of virus cycle

Answer 17

Attachment, penetration, uncoating/replication, release of viral proteins

Question 18

What are non-specific electrostatic binding molecules & why are they important?

Answer 18

• dextran, heparin sulfate, protoglycans
• assist in attachment stage

Question 19

What are the specific binding molecules that are used during the attachment stage & their importance

Answer 19

Cell surface receptors determine virus tropism

Question 20

Binding of FIV to CD4 involves interactions between

Answer 20

Gp120 and CD4

Question 21

Which viruses don’t require receptors

Answer 21

Viroids

Question 22

2 methods of penetration for enveloped viruses

Answer 22

Endocytosis (influenza virus) & plasma/endosomal membrane fusion (FIV, reoviruses)

Question 23

2 methods of penetration for non-enveloped viruses

Answer 23

Pore entry(enteroviruses), lysis of cell endosomal membrane(adenovirus)