MIDTERM LEC 3: BASIC CONCEPTS OF VIROLOGY

Question 1

The word “virus” came from which Latin word?

Answer 1

vīrus

Question 2

Vīrus means

Answer 2

poisonous fluid
or venom

Question 3

Submicroscopic, obligate intracellular
parasite, and among the smallest of all infectious agents

Answer 3

virus

Question 4

What does “obligate intracellular parasite” mean?

Answer 4

they cannot grow outside of living cells

Question 5

T/F: Viruses are the most frequent cause of human infectious disease

Answer 5

T

Question 6

T/F: There is NO viral infection among any animals, plant, or bacterial cell

Answer 6

F

Question 7

Brick shaped virus with hollow spikes

Answer 7

poxviruses

Question 8

Largest and most complex virus

Answer 8

poxviruses

Question 9

Size of poxviruses

Answer 9

250x350nm

Question 10

Smallest human virus

Answer 10

poliovirus

Question 11

Size of poliovirus

Answer 11

25nm

Question 12

Poliovirus belong to what family

Answer 12

picornaviridae

Question 13

Smallest DNA virus

Answer 13

parvovirus

Question 14

Largest RNA virus

Answer 14

paramyxovirus

Question 15

T/F: Viruses can contain RNA or DNA at the same time

Answer 15

F (either of the 2 only, never both)

Question 16

How many families of virus are associated with human infections?

Answer 16

21

Question 17

How many families of RNA viruses are associated with human infections?

Answer 17

14

Question 18

How many families of DNA viruses are associated with human infections?

Answer 18

7

Question 19

T/F: Viruses can multiply by binary fission

Answer 19

F (they cannot)

Question 20

Refers to the specificity of viruses and how they can only infect a limited number of hosts.

Answer 20

viral tropism

Question 21

Enumerate the viral mode of transmission

Answer 21

● Fecal-oral route
● Sexual contact
● Trauma or injection of contaminated objects ●Tissue transplants (BT)
● Arthropod or animal bites
● Transplacental

Question 22

Local infection leads to ________ then to other tissues (systemic)

Answer 22

viremia

Question 23

Viruses that have the ability to stimulate uncontrolled growth of host cells

Answer 23

oncogenic viruses (cancerous)

Question 24

The classification system of virus is determined by what committee

Answer 24

International Committee on
Taxonomy of Viruses (ICTV)

Question 25

The ICTV classification system is based on what 2 properties

Answer 25

chemical and physical properties (like genome type, # of proteins encoded, nucleic acid sequence, virion shape, capsid shape, envelope, etc.)

Question 26

In general, how many taxonomic ranks are widely used?

Answer 26

5

Question 27

What are the widely used 5 taxonomic ranks?

Answer 27

- order - family - subfamily - genus - species

Question 28

Suffix used for the taxonomic rank "order"

Answer 28

-virales

Question 29

Suffix used for the taxonomic rank "families"

Answer 29

-viridae

Question 30

Suffix used for the taxonomic rank "subfamilies"

Answer 30

-virinae

Question 31

Suffix used for the taxonomic rank "genus"

Answer 31

-virus

Question 32

T/F: Classification of viral species can be problematic and therefore is often polythetic

Answer 32

T

Question 33

Polythetic meaning

Answer 33

members of the group may share common characteristics but may not have a single defining characteristic

Question 34

3 basic properties in viral classification

Answer 34

- viral morphology - method of replication - presence or absence of lipid envelope

Question 35

Classification system that is based on the type of nucleic acid genome and replication strategy of the virus

Answer 35

baltimore classification system

Question 36

Baltimore classification system was devised by a Nobel laureate named

Answer 36

David Baltimore

Question 37

In what year was the baltimore classification system devised?

Answer 37

1970

Question 38

Baltimore classification system was based on

Answer 38

- the type of nucleic acid genome - replication strategy of the virus

Question 39

Viruses are classified into how many classes

Answer 39

7 classes

Question 40

Class I

Answer 40

dsDNA viruses

Question 41

Class II

Answer 41

ssDNA viruses

Question 42

Class III

Answer 42

dsRNA viruses

Question 43

Class IV

Answer 43

positive sense ssRNA viruses

Question 44

Class V

Answer 44

negative-sense ssRNA viruses

Question 45

Class VI

Answer 45

RNA viruses that reverse transcribe

Question 46

Class VII

Answer 46

DNA viruses that reverse transcribe

Question 47

Complete infectious viral particles

Answer 47

virions

Question 48

Viral structure that constitutes the genetic material or viral genome which can be single or double stranded DNA or RNA

Answer 48

nucleic acid core

Question 49

Viral structure that introduces viral genome into host cell

Answer 49

capsomere

Question 50

It protects viral genome/nucleic acid core against destructive agent external environment

Answer 50

capsomere

Question 51

Complex morphologic units of the capsomere which consist of several identical or different protein molecules

Answer 51

capsid

Question 52

Protein shell, or coat, that encloses the nucleic acid genome

Answer 52

capsid

Question 53

This is a repeating structural unit

Answer 53

capsomere

Question 54

Types of capsids in symmetry

Answer 54

- helical capsid - icosahedral capsid

Question 55

Type of capsid that is cubical and has 20 flat sides

Answer 55

icosahedral capsid

Question 56

Type of capsid that is irregular

Answer 56

helical capsid

Question 57

Nucleic acid genome surrounded by a symmetric protein

Answer 57

nucleocapsid

Question 58

Lipoprotein envelope that covers the capsid and is acquired from the host cell

Answer 58

peplos/viral envelope

Question 59

host cell membrane/plasma membrane/nucleic acid membrane

Answer 59

peplos/viral envelope

Question 60

What do you call a virus with envelop

Answer 60

enveloped virus

Question 61

What do you call a virus with no envelope

Answer 61

naked virus

Question 62

What type of virus is susceptible to inactivation such as high temperature, high pH

Answer 62

enveloped virus

Question 63

Enveloped virus may contain what protein, which lies between the envelope and nucleocapsid?

Answer 63

matrix protein

Question 64

Glycoprotein molecules that bind to host cell during attachment

Answer 64

glycoprotein spikes

Question 65

Glycoprotein spikes are readily visible under what type of microscope?

Answer 65

electron microscope

Question 66

Viruses with glycoprotein spikes

Answer 66

- SARS-CoV-2 - HIV (Human Immunodeficiency Virus) - EBV (Epstein-Barr Virus)

Question 67

Target receptor of HIV

Answer 67

CD4

Question 68

Target of SARS-CoV-2

Answer 68

ACE

Question 69

Target receptor of EBV

Answer 69

C3D

Question 70

Occurs when a virus infects a host cell by which proliferation of viral genomes transpire to cause further infection to the host's body, resulting in a disease or infection

Answer 70

viral replication

Question 71

Enumerate in order the infectious cycle of virus

Answer 71

1. Attachment 2. Penetration 3. Uncoating 4. Macromolecular Synthesis 5. Assembly 6. Release (APUMAR)

Question 72

AKA adsorption

Answer 72

attachment

Question 73

It is where the recognition of a suitable, specific host cell occurs (viral tropism)

Answer 73

attachment

Question 74

What must adsorb or attach to the cell surface since viruses are unable to diffuse across biological membranes?

Answer 74

virions

Question 75

Why do viruses can't diffuse across biological membranes?

Answer 75

because virus particles are too large to diffuse across the plasma membrane

Question 76

The virus attaches to specific receptors on the surface of a susceptible cell by means of specialized structures on its surface, called?

Answer 76

adhesion molecules

Question 77

AKA viral entry

Answer 77

penetration

Question 78

Provides an opportunity to internalize the virus

Answer 78

penetration

Question 79

Virus enters the host cell by several mechanisms that are virus-dependent. Enumerate the mechanisms

Answer 79

- Direct penetration - Fusion method - Receptor-mediated endocytosis

Question 80

A penetration mechanism in which the viral envelope fuses with the host’s plasma membrane

Answer 80

fusion method

Question 81

A penetration mechanism which is possible for naked viruses

Answer 81

direct penetration

Question 82

A single cell with several nuclei

Answer 82

syncytia

Question 83

In this mechanism, there is a binding of infected host cells with nearby host cells, forming syncytia

Answer 83

fusion method

Question 84

A penetration mechanism that involves phagocytosis by the host cell; most common mechanism of viral penetration.

Answer 84

receptor-mediated endocytosis

Question 85

The breakdown/removal of the capsid, causing the release of the virus genome into the cell

Answer 85

uncoating

Question 86

T/F: Uncoating do not occur simultaneously along with or just after penetration

Answer 86

F (they occur simultaneously or just after penetration)

Question 87

Once the virus loses its protein coat, it releases its

Answer 87

viral genome

Question 88

RNA viruses are released in the

Answer 88

cytoplasm

Question 89

DNA viruses are released in the

Answer 89

nucleus

Question 90

T/F: The virus forces the host cell to make millions of copies that leave the cell and spread

Answer 90

T