Virology

Question 1

TERMS AND DEFINITIONS: lipid-containing membrane that surrounds some virus particles Acquired during viral maturation
by a budding process through a cellular membrane.

Answer 1

Envelope

Question 2

TERMS AND DEFINITIONS: virus particle that is functionally deficient in some aspect of replication.

Answer 2

Defective Virus

Question 3

TERMS AND DEFINITIONS: Morphologic units seen in the electron microscope on the
surface of icosahedral virus particles.

Answer 3

Capsomeres

Question 4

TERMS AND DEFINITIONS: protein shell, or coat, that encloses the nucleic acid genome.

Answer 4

Capsid

Question 5

• smallest infectious agents ranging from about 20nm to
  about 300 nm in diameter.
• Contains only one kind of nucleic acid (RNA or DNA) as their
  genome.
• parasites at the genetic level, replicating only in living cells and are inert in the extracellular environment

Answer 5

VIRUSES

Question 6

PRIONS: SIZE, REPLICATION, CELLWALL, DOMAIN.

Answer 6

Size: EM
Replication: Misfolded proteins causes misfolding of neighboring proteins.
Cellwall: None
Domain: Non- Cellular

Question 7

VIRUSES: SIZE, REPLICATION, CELLWALL, DOMAIN.

Answer 7

Size: EM
Replication: Nucleic acid replication using host mechanisms.
Cellwall: Protein capsid, some have host cell envelope.
Domain: Non- Cellular

Question 8

BACTERIA: SIZE, REPLICATION, CELLWALL, DOMAIN.

Answer 8

Size: Micro
Replication: Binary fission
Cellwall: G (+) inner membrane & thick peptidoglycan G (-) inner and outer cell membranes & mid thin peptidoglycan sterols.
Domain: Bacteria

Question 9

FUNGI: SIZE, REPLICATION, CELLWALL, DOMAIN

Answer 9

Size: Micro to Gross
Replication: Asexual budding, Sexual Mating (Spores)
Cellwall: Ergosterol Chitin cell wall
Domain: Eukaryota

Question 10

PARASITES: SIZE, REPLICATION, CELLWALL, DOMAIN

Answer 10

Size: Micro to Gross
Replication: Asexual and Sexual
Domain: Eukaryota

Question 11

TERMS AND DEFINITIONS: Virus-encoded glycoproteins exposed on the surface of the envelope.

Answer 11

Peplomers

Question 12

TERMS AND DEFINITIONS: protein–nucleic acid complex representing the
packaged form of the viral genome.
- Term commonly used in cases in which the
nucleocapsid is a substructure of a more
complex virus particle.

Answer 12

Nucleocapsid

Question 13

TERMS AND DEFINITIONS: basic protein building
blocks of the coat.
usually a collection of more than one non-identical protein subunit. The Protomer - structural unit

Answer 13

Structural units

Question 14

TERMS AND DEFINITIONS: single folded viral polypeptide chain.

Answer 14

Subunits

Question 15

TERMS AND DEFINITIONS: complete virus particle; serves to transfer the viral nucleic acid from one cell
to another.

Answer 15

Virion

Question 16

Classification of Viruses: gene order, number and
position of open reading
frames, strategy of
replication (patterns of
transcription, translation), and cellular sites (accumulation of proteins, virion assembly, virion
release).Classification of Viruses:

Answer 16

Genome organization and replication

Question 17

Classification of Viruses: number, size, amino acid
sequence, modifications
(glycosylation,
phosphorylation,
myristoylation), and
functional activities of
structural and nonstructural proteins
(transcriptase, reverse
transcriptase, neuraminidase, fusion
activities)

Answer 17

Virus protein properties

Question 18

Classification of Viruses: reactions to various antisera.

Answer 18

Antigenic properties

Question 19

Classification of Viruses: molecular mass, buoyant density, pH stability, thermal stability, and susceptibility to physical
and chemical agents,
especially solubilizing
agents and detergents.

Answer 19

Physicochemical
properties of the virion

Question 20

TERMS AND DEFINITIONS: natural host range, mode
of transmission, vector
relationships,
pathogenicity, tissue
tropisms, and pathology.

Answer 20

Biologic properties

Question 21

Classification of Viruses: size, shape, type of
symmetry, presence or
absence of peplomers, and presence or absence of
membranes.

Answer 21

Virion morphology

Question 22

Classification of Viruses: type of nucleic acid (DNA or RNA), size of the genome, strandedness (single or double), whether linear or circular, sense (positive,
negative, ambisense),
segments (number, size),
nucleotide sequence,
percent GC content, and presence of special
features (repetitive
elements, isomerization,
5ʹ-terminal cap, 5ʹ-terminal covalently linked protein, 3ʹ- terminal poly(A)
tract).

Answer 22

Virus genome properties

Question 23

Types of Symmetry of Virus Particles: Most animal viruses are of icosahedral pattern
Icosahedron – closed shell composed of 20 facets of equilateral triangles, 12 vertices, and fivefold, threefold, and
twofold axes of rotational symmetry
For viruses, these facets are the morphological units and are
usually encoded by the assembly units
Spontaneously assembles into a sphere
Most viruses that have icosahedral symmetry do not have an icosahedral shape—rather, the physical appearance
of the particle is spherical. Both DNA and RNA viral groups exhibit examples of cubic
symmetry.

E.g., Poliovirus Type 1 (Mahoney strain), adenoviruses

Answer 23

Cubic Symmetry

Question 24

Types of Symmetry of Virus Particles: Found in filamentous viruses (e.g. Ebola virus, orthomyxoviruses)
- The protein subunits assemble only in
the presence of nucleic acid (unlike
cubic).

-All known examples of animal viruses
with helical symmetry

-contain RNA genomes

-Exception: rhabdoviruses, have flexible
nucleocapsids that are wound into a
ball inside envelopes

Answer 24

Helical Symmetry

Question 25

Types of Symmetry of Virus Particles: Some viruses have pleiomorphic shapes and are more complicated in structure (e.g. poxviruses) Poxviruses are brick shaped with a dumbbell structure in the center

Answer 25

Complex Symmetry

Question 26

Virus Symmetry: These viruses resemble a crystal and are calledicosahedral virus. Example: adenoviruses.

Answer 26

Cubical symmetry

Question 27

Virus Symmetry: In which the particle is elongated. Most helical viruses are enveloped . Example: influenza virus.

Answer 27

Helical symmetry

Question 28

Virus Symmetry: In which the viruses are complicated in structure. Example: poxviruses and bacteriophage.

Answer 28

Complex symmetry

Question 29

CHEMICAL COMPOSITION OF VIRUSES: All have structural proteins, some have enzymes Viral proteins are principal targets of the immune response

Answer 29

Proteins

Question 30

CHEMICAL COMPOSITION OF VIRUSES: DNA or RNA Single or double-stranded Positive- or negative - stranded or ambisense Ambisense carries negative or positive (Hep B) Contiguous or segmented

Answer 30

Nucleic acids

Question 31

CHEMICAL COMPOSITION OF VIRUSES: Some viruses have lipid envelopes acquired from the cell in which the virus was produced

Answer 31

Lipids

Question 32

CHEMICAL COMPOSITION OF VIRUSES: Some viral proteins, particularly those that protrude outward, have carbohydrate groups These groups often mediate virus attachment to susceptible cells

Answer 32

Glycoproteins

Question 33

CULTIVATION AND DETECTION OF VIRUSES: Cell grown in vitro: made by dispersing cells (Usually with trypsin) fromfreshly removed host tissues. In general, they are unable to grow for more than a fewpassages in culture

Answer 33

Primary cultures

Question 34

CULTIVATION AND DETECTION OF VIRUSES: Cell grown in vitro: made by dispersing cells (Usually with trypsin) fromfreshly removed host tissues. In general, they are unable to grow for more than a few passages in culture

Answer 34

Primary cultures

Question 35

CULTIVATION AND DETECTION OF VIRUSES: Cell grown in vitro: Diploid cell lines that haveundergone a change that allows their limited culture (up to 50 passages) but that retain their normal chromosome pattern.

Answer 35

Secondary cultures

Question 36

CULTIVATION AND DETECTION OF VIRUSES: Cell grown in vitro: cultures capable of more prolonged (indefinite)growth that have been derived from diploid cell lines or from malignant tissues. have altered and irregular numbers of chromosome.

Answer 36

Continuous cell lines

Question 37

DETECTION OF VIRUS-INFECTED CELLS: cell lysis or necrosis, inclusion body formation, giant cell formation, and cytoplasmic vacuolization. (ie, morphologic changes in the cells

Answer 37

Development of cytopathic effects

Question 38

DETECTION OF VIRUS-INFECTED CELLS: Specific antisera can be used to detect the synthesis of viral proteins in infected cells. Ex: hemagglutinin of influenza virus protein

Answer 38

Appearance of a virusencoded

Question 39

DETECTION OF VIRUS-INFECTED CELLS: Molecular-based assays such as polymerase chain reaction provide rapid, sensitive, and specific methods of detection

Answer 39

Detection of virus-specific nucleic acid

Question 40

DETECTION OF VIRUS-INFECTED CELLS: reaction becomes positive before cytopathic changes are visible and, in some cases, occurs in the absence of cytopathic effects

Answer 40

Adsorption of erythrocytes to infected cells, called hemadsorption, caused by the presence of virusencoded hemagglutinin (parainfluenza, influenza) in cellular membranes.

Question 41

DETECTION OF VIRUS-INFECTED CELLS: result in death of the embryo (eg, encephalitis viruses), production of pocks or plaques on the chorioallantoic membrane (eg, herpes, smallpox, and vaccinia), or development of hemagglutinins in the embryonic fluids or tissues (eg, influenza).

Answer 41

Viral growth in an embryonated chick egg.

Question 42

IDENTIFICATION OF A PARTICLE AS A VIRUS: prepared against the infectious virus should react with the characteristic particle and vice versa. Direct observation of an unknown virus can be accomplished by electron microscopic examination of aggregate formation in a mixture of antisera and crude viral suspension

Answer 42

Antisera

Question 43

REACTION TO PHYSICAL AND CHEMICAL AGENTS: heat inactivate some viruses, while cold usually preserves them

Answer 43

Heat and cold

Question 44

REACTION TO PHYSICAL AND CHEMICAL AGENTS: Many viruses can be stabilized by salts in order to resist heat inactivation, which is important in the preparation of vaccines

Answer 44

Stabilization by salts

Question 45

REACTION TO PHYSICAL AND CHEMICAL AGENTS: - pH Viruses are usually stable between pH values of 5.0 and 9.0 Some viruses (eg, enteroviruses) are resistant to acidic conditions. -All viruses are destroyed by alkaline conditions. - Hemagglutination reactions can be quite sensitive to changes in pH

Answer 45

pH

Question 46

REACTION TO PHYSICAL AND CHEMICAL AGENTS: damages nucleic acids; crosslinks viral

Answer 46

Radiation

Question 47

REACTION TO PHYSICAL AND CHEMICAL AGENTS: ether is an organic solvent, thus damages envelope membranes of viruses

Answer 47

Ether susceptibility

Question 48

REACTION TO PHYSICAL AND CHEMICAL AGENTS: amphipathic, thus solubilized membranes and can dissociate noncovalent bonds between viral proteins

Answer 48

Detergents

Question 49

REACTION TO PHYSICAL AND CHEMICAL AGENTS: cross-links nucleic acids and proteins; destroys viral infectivity

Answer 49

Formaldehyde

Question 50

REACTION TO PHYSICAL AND CHEMICAL AGENTS: Dyes bind to the viral nucleic acid then virus becomes susceptible to Inactivation inactivation by visible light.

Answer 50

Photodynamic Inactivation

Question 51

REACTION TO PHYSICAL AND CHEMICAL AGENTS: Antibacterial antibiotics and sulfonamides have no effect on viruses. Larger concentrations of chlorine are required to destroy viruses than to kill bacteria, especially in the presence of extraneous proteins.

Answer 51

Antibiotics and Other Antibacterial antibiotics