Chapter 29 - General Properties of Viruses

Question 0

It is acquired when the viral nucleocapsid buds through a cellular membrane in the course of maturation

Answer 0

Lipid

Question 1

Lipids in viral membranes are derived from?

Answer 1

Host cell

Question 2

Occurs only at sites where virus-specific proteins have been inserted into the host cell membrane

Answer 2

Budding

Question 3

Proteins that are protruding from the envelope and exposed on the external surface of the virus particle

Answer 3

Viral glycosylated proteins

Question 4

Proteins that are underneath the envelope that anchor the particle together

Answer 4

Viral unglycosylated proteins

Question 5

Viruses that are sensitive to treatment with ether and other organic solvents

Answer 5

Lipid-containing viruses

Question 6

Viruses that are generally resistant to ether

Answer 6

Nonlipid-containing viruses

Question 7

Viral envelopes contain ________

Answer 7

glycoproteins

Question 8

Enzymes that cleave DNA at specific nucleotide sequences

Answer 8

Restriction endonucleases

Question 9

The entire infectious unit is termed ________.

Answer 9

virion

Question 10

True or false. The viruses are inert in the extracellular environment.

Answer 10

True

Question 11

What encases and stabilizes the viral nucleic acid against the ECE and facilitates the attachment and penetration by the virus

Answer 11

Capsid

Question 12

The viruses that attack bacteria

Answer 12

Bacteriophages

Question 13

Morphologic units on the surface of icosahedral virus particles that represent clusters of polypeptides

Answer 13

Capsomeres

Question 14

A virus particle that is functionally deficient in some aspect of replication

Answer 14

Defective virus

Question 15

Basic building blocks of the coat

Answer 15

Structural units

Question 16

A single folded viral polypeptide chain

Answer 16

Subunit

Question 17

Two theories of viral origin

Answer 17

Derived from DNA or RNA nucleic acid components

Degenerate forms of intracellular parasites

Question 18

Performed early in virus identification

Answer 18

Genome sequencing

Question 19

Basis of Classification

Answer 19

• Virion morphology
• Virus genome properties
• Genome organization and Replication
• Virus protein properties
• Antigenic properties
• Physicochemical properties
• Biologic properties

Question 20

Virus family names have the suffix

Answer 20

-viridae

Question 21

Genus names carry the suffix

Answer 21

-virus

Question 22

The ______________________________________ had organized more than 4000 animal and plant viruses

Answer 22

International Committee on Taxonomy of Viruses

Question 23

Ex. of heavy metal stain to emphasize surface structure

Answer 23

Potassium phosphotungstate

Question 24

The heavy metal permeates the virus particle like a cloud and brings out the surface structure of viruses by virtue of ___________

Answer 24

"Negative staining"

Question 25

The typical level of resolution

Answer 25

3-4 nm

Question 26

Uses virus samples quick frozen in vitreous ice

Answer 26

Cryoelectron microscopy

Question 27

Can provide atomic resolution info, generally at a level of 0.2-0.3 nm

Answer 27

X-ray crystallography

Question 28

Types of arrangement of morphologic subunits

Answer 28

Cubic symmetry Helical symmetry Complex structures

Question 29

The most efficient arrangement for subunits in a closed shell

Answer 29

Icosahedral pattern

Question 30

Describe the icosahedron

Answer 30

20 faces (each an equi triangle), 12 vertices, fivefold, threefold, and twofold axes of rotational symmetry, vertex units have five neighbors (pentavalent) and others six (hexavalent)

Question 31

How many identical subunits on the surface of an icosahedron

Answer 31

60

Question 32

Physical appearance of most viruses with icosahedral symmetry

Answer 32

Spherical

Question 33

Involved in the condensation of the nucleic acid into a form suitable for packaging

Answer 33

Cellular histones

Question 34

"__________________" on viral nucleic acid are involved in assembly into virus particles

Answer 34

Packaging sequences

Question 35

Expression of ______ proteins from cloned genes often results in self-assembly and formation of empty virus-like particles.

Answer 35

capsid

Question 36

Viral architecture where protein subunits are bound in a periodic way to the viral nucleic acid, winding it into a helix

Answer 36

Helical symmetry

Question 37

True or false. It is possible for "empty" helical patterns to form.

Answer 37

False

Question 38

All known examples of animal viruses with helical symmetry contain (a. DNA b. RNA) genomes.

Answer 38

b. RNA

Question 39

Classic attributes of viruses

Answer 39

Small size | Ability to pass through filters

Question 40

Most widely used method for estimating particle size

Answer 40

Direct observation in the electron microscope

Question 41

Another method in determining particle size aside from the use of the EM

Answer 41

Sedimentation in the ultracentrifuge

Question 42

Virus range in diameter from about

Answer 42

20 nm to 300 nm

Question 43

Particles with a twofold difference in diameter have an ___________ difference in volume

Answer 43

eightfold

Question 44

What virus has a greater mass, the poxvirus or the poliovirus?

Answer 44

Poxvirus

Question 45

Their major purpose is to facilitate transfer of the viral nucleic acid from one host cell to another.

Answer 45

Structural proteins

Question 46

Fxns of structural proteins

Answer 46

- protect the viral genome against inactivation by nucleases - participate in the attachment of the virus particle to a susceptible cell - provide the structural symmetry of the virus particle

Question 47

An enzyme in retroviruses that makes a DNA copy of the viral RNA

Answer 47

Reverse transcriptase

Question 48

An enzyme carried by viruses with negative-sense RNA genome that is needed to copy the first mRNAs

Answer 48

RNA polymerase

Question 49

All major (a. DNA b. RNA) viral groups have a linear or circular configuration

Answer 49

a. DNA

Question 50

True or false. The isolated RNA of the negative-sense RNA viruses is infectious.

Answer 50

False

Question 51

Hypothesized the existence of infectious agents too small to be seen by a light microscope

Answer 51

Jacob Henle

Question 52

People responsible for sterile culture

Answer 52

Louis Pasteur and Robert Koch

Question 53

German; described a non-fungal cause of tobacco mosaic disease; performed limiting dilution and determined that it was not a toxin

Answer 53

Adolf Mayer

Question 54

Discovered the first filterable human infectious agent in cuba

Answer 54

Walter Reed

Question 55

Cannot replicate on its own; needs to utilize host cell

Answer 55

Obligate intracellular parasite

Question 56

genome + capsid

Answer 56

naked virus

Question 57

genome + capsid + envelope

Answer 57

Enveloped virus

Question 58

Carrier of genetic material; either RNA or DNA but not both

Answer 58

Genome

Question 59

Classification of genome

Answer 59

- segmented | - non-segmented

Question 60

Classification of DNA/RNA

Answer 60

- double stranded | - single stranded

Question 61

Movement of positive (+) coiling

Answer 61

Counterclockwise

Question 62

Movement of negative (-) coiling

Answer 62

Clockwise

Question 63

Icosahedral structure often posses _____ viruses

Answer 63

naked

Question 64

An example of an enveloped virus having an icosahedral capsid

Answer 64

Herpes virus

Question 65

May have arisen from transposable elements

Answer 65

Retroviruses

Question 66

Different wild isolates of the same virus

Answer 66

Strain

Question 67

Distinct strain of the same virus based upon known genetic difference

Answer 67

Type

Question 68

A virus that behaves differently in the laboratory than the wild type due to unknown reasons

Answer 68

Variant