Chapter 31 - Intro to Virology and Phage

Question 1

describe viruses

Answer 1

• simple organization
  -DNA or RNA genome
• unable to reproduce outside of living cells
• obligate intracellular parasites

Question 2

describe cellular organisms

Answer 2

• complex organization
• DNA genome and RNAs
• carry out cell division
• some are obligate intracellular parasites

Question 3

what are the 3 theories of viral origin

Answer 3

• reductive origin: viruses evolved by degenerative evolution from intracellular parasitic cells
• theory of intracellular origin: viruses evolved from functional parts of cells that acquired an ability to reproduce themselves uncontrolled by the cell
• theory of independent origin holds that viroid nucleic acids could have evolved outside of cells during the RNA world and acquired the ability to infect cells

Question 4

how big are pandoraviruses

Answer 4

1000nm

Question 5

what is the biggest virus

Answer 5

pandora virus

Question 6

multicomponent viruses genomes are segmented and the segments are distributed into _____

Answer 6

separate viral particles

Question 7

cultivation of viruses requires inoculation of living host cells. what are examples of the host cells

Answer 7

• suitable animals
• embryonated eggs
• tissue cultures
• cytopathic effects (CPEs)

Question 8

what can tissue (cell) cultures be

Answer 8

• monolayers of animal cells
• plaques: localized area of cellular destruction and lysis

Question 9

what are cytopathic effects (CPEs)

Answer 9

microscopic or macroscopic degenerative changes or abnormalities in host cells and tissues

Question 10

what makes up a nucleocapsid/naked capsid virus

Answer 10

• DNA or RNA + structural proteins +/- enzymes and nucleic acid binding proteins

Question 11

what makes up an enveloped virus

Answer 11

nucleocapsid + glycoproteins and membrane

Question 12

what makes up icosahedral symmetry

Answer 12

• nucleocapsid made of
• capsid
• capsomers
• nucleic acids

Question 13

what virus has icosahedral capsid symmetry

Answer 13

herpes

Question 14

what is an example of a virus with helical symmetry

Answer 14

ebola virus filaments (SEM)

Question 15

what do enveloped viruses have vs nonenveloped

Answer 15

glycoprotein spikes and lipid bilayer

Question 16

what is an example of an asymmetrical virus

Answer 16

vaccinia poxvirus

Question 17

what are the groups of RNA viruses

Answer 17

nonenveloped vs enveloped

Question 18

what are the groups of nonenveloped RNA viruses

Answer 18

-single stranded positive sense
- double stranded

Question 19

what are the groups of enveloped RNA viruses

Answer 19

-single stranded positive sense
- single stranded negative sense
- retrovirus

Question 20

what properties are used to classify viruses

Answer 20

• type and structure of nucleic acid used for viral genome
• presence or absence of envelope
• type of capsid symmetry
• replication strategy

Question 21

what are the groups of DNA viruses

Answer 21

nonenveloped and enveloped

Question 22

what are the groups of nonenveloped DNA viruses

Answer 22

• single stranded linear
• double stranded linear
• double stranded circular

Question 23

what are the groups of enveloped DNA viruses

Answer 23

• double stranded linear
• double stranded circular

Question 24

what are the steps of virus replication

Answer 24

• adsorption
• penetration and uncoating
• synthesis of viral proteins and nucleic acids
• assembly of virons
• release

Question 25

what is adsorption of virions

Answer 25

viral surface proteins and/or enzymes mediate attachment to specific host receptors

Question 26

what are the 3 mechanisms of penetration and uncoating

Answer 26

- injection of nucleic acid - fusion of envelope with host membrane - endocytosis

Question 27

describe the assembly of virus capsids

Answer 27

- capsid proteins: encoded by late genes - assembly of naked viruses: empty procapsids formed then nucleic acid inserted - assembly of enveloped viruses: similar to assembly of naked viruses - site of morphogenesis varies

Question 28

describe virion release of naked viruses and enveloped viruses

Answer 28

- naked viruses: usually by lysis of host cells - enveloped viruses: formation of envelope and release usually occur concurrently

Question 29

what are virus encoded proteins incorporated into

Answer 29

host membrane

Question 30

what are the virus replication events during a single infectious cycle

Answer 30

- attachment - disassembly - replication - assembly

Question 31

which type of infection has the highest number of virus in tissues: acute, chronic or latent

Answer 31

acute then chronic then latent

Question 32

what are other principles of viral disease

Answer 32

- viral spread and replication - host factors in defense and damage - diagnosis - emerging viruses

Question 33

are bacteriophages a part of the human virome

Answer 33

yes

Question 34

what is the bacterial product from prophage "phage C1"

Answer 34

botulinum toxin

Question 35

what is the bacterial product of beta phage

Answer 35

diptheria toxin

Question 36

what is the bacterial product of epsilon 34

Answer 36

LPS synthesis

Question 37

what is the human protein or regulator provided by HERV-W

Answer 37

syncythin 1

Question 38

what is the human protein or regulator provided by HERV-E

Answer 38

apolipoprotein C1

Question 39

describe the bacteriophage replication cycle: slow release

Answer 39

a filamentous phage produces phage particles without lysing the cell - the host continues to reproduce itself but more slowly than uninfected cells because many of its resources are being used to make phages

Question 40

what are the bacterial defenses against bacteriophages

Answer 40

- genetic resistance- mutations in bacterial genes - restriction endonucleases- enzymes that cut invading DNA - CRISP- a bacterial immune system

Question 41

why is phage therapy being explored as antibiotic treatment

Answer 41

- phages may limit bacterial numbers to levels that the immune system can tolerate - phage particles may modulate immune system activity - phages may attack biofilms