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Virology > Test 1 > Flashcards

Test 1 Flashcards

1
Q

What is virology?

A

the study of viruses

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2
Q

When did the sizes and shapes of the viruses become known?

A

late 1930s

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3
Q

Why weren’t the sizes and shapes of the viruses discovered before the 1930’s? What inhibited this?

A

couldn’t see it under a light microscope so they had to wait for the electron microscope

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4
Q

What are 4 general characteristics of viruses?

A
  1. They are SMALL
  2. Need a LIVING cell
  3. Have either DNA or RNA genome…but not both
  4. Have a RECEPTOR BINDING PROTEIN
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5
Q

What is the range in size for how small a virus is in diameter?

A

20-150nm

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6
Q

Why do viruses need a living cell

A

the virus itself is considered to not be living so it needs a prokaryotic or eukaryotic organism to replicate and survive

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7
Q

Why do viruses need a receptor binding protein

A

thats how they bind and infect a cell, the binding protein allows them to get on the surface of a virus

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8
Q

What are the 3 main components of a virus

A
  1. nucleic acid
  2. protein coat
  3. may or may not have a lipid envelope
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9
Q

What is the one goal of a virus

A

to deliver its genome to host cell which then causes hosts genes to make virus parts

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10
Q

How many genes do viruses have

A

at most 10 genes

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11
Q

What type of nucleic acid do viruses have

A

DNA or RNA

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12
Q

Viral genomes range in size from how many basepairs

A

3000 to 200,000

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13
Q

DNA viruses have what type of genome

A

double stranded

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14
Q

How are DNA viruses made into proteins (basic steps)

A

transcribed into mRNA

translated into protein

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15
Q

What type of genome do RNA viruses have

A

single stranded

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16
Q

Which is more stable? DNA or RNA?

A

DNA is more stable due to having double strand

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17
Q

Why does RNA change more rapidly than DNA genomes?

A

less stable

in DNA there is excess backtracking and proofreading and repair mechanisms that don’t exist in RNA

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18
Q

Why does RNA have the backtracking and repair mechanisms

A

because RNA is an intermediate typically while DNA goes through meiosis and mitosis after being copied

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19
Q

RNA genomes can be one of what two things?

A

positive or negative stranded

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20
Q

What is different about the steps in positive vs negative stranded RNA

A

positive- directly translated to protein, it is already mRNA

negative-contain complimentary sequence to positive strand (ex. retrovirus)

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21
Q

How is a retrovirus translated

A

converted back to DNA and then back into the correct strand of RNA then translated into a protein

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22
Q

What type of polymerase do humans have?

A

DNA dependent RNA polymerase

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23
Q

What type of polymerase does RNA genome need

A

RNA dependent RNA polymerase

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24
Q

Since humans do not have the RNA dependent RNA polymerase, how does the virus get this?

A

It brings it along with its genome when it attacks human cell

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25
Q

What is another name for the protein coat

A

capsid

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26
Q

What are subunits of the capsid

A

capsomeres

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27
Q

What are the two general shapes of viruses protein coat

A

helical

icosohedral

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28
Q

What is a helical shaped coat

A

arranged like a spiral staircase

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29
Q

What is a icosohedral shaped coat

A

triangular shape, looks like a golfball

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30
Q

What does the nucleic anid and capsid make

A

nucleocapsid

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31
Q

Why do some viruses have a lipid envelope?

A

they take some of the cell membrane with them as they replicate (have spike membrane proteins that take some of the host membrane with them)

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32
Q

How do viruses have spike proteins

A

they get them through its coding from the viral genome

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33
Q

What specific function do the spike proteins have

A

receptor binding protein for viruses

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34
Q

What is a virion

A

nucleocapsid and envelope

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35
Q

What four features are applied to viral classification (named for its characteristics)

A

1- genome type
2- polarity of genome (+ or -)
3- symmetry of nucleocapsid
4-presence or absence of envelope

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36
Q

Why can’t viruses duplicate like a human cell

A

they don’t have any of the machinery and mechanisms to duplicate

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37
Q

Why do viruses use a host cell

A

to get the machinery needed for replication

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38
Q

Could viruses exist before cells

A

no

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39
Q

How do viruses know which cell to attach to? Is it random?

A

no the binding is not random. viruses have specific spike proteins that interact with host cell receptors

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40
Q

Do host cells have specific viral receptors

A

no

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41
Q

If the cell does not have specific viral receptors, how do viruses attach

A

the virus attacks the cell using one of its existing receptors and then it acquires the ability to use that receptor

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42
Q

What are the ten steps for duplication of a virus

A 
1- host cell recognition and binding
2-internalization (endocytose)
3-"uncoating"
4-transcription (unless positive)
5-translation of early genes
6-early genes function
7- genome replication
8-translation of late genes
9-assembly
10-release
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43
Q

What does the step of uncoating allow

A

genome to get to the cell

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44
Q

What are early genes

A

typically enzymatic functions that play a part in the duplication process

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45
Q

What are the two major things needed to get more virus

A

more genome= more transcribed

more viral proteins expressed from the genome

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46
Q

What are late genes

A

those typically involved with structure

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47
Q

What do viruses have on their surface that aids them in the 1st step of replication

A

receptor binding proteins

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48
Q

What do the receptor binding proteins do to the host cell

A

bind to normal functional receptors and exploit their location

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49
Q

The binding that occurs between the receptor and binding protein are what two things

A

specific and strong

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50
Q

What is meant that the binding is specific

A

each type of virus only infects certain types of cells

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51
Q

What is meant that the binding is strong

A

its a biochemical event that produces strong interactions

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52
Q

What occurs in the 2nd step of replication

A

internalization, the virus gets into the cell

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53
Q

What are the 2 general ways of internalization

A

fusion and receptor mediated endocytosis

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54
Q

What is the fusion method of internalization

A

viral membrane becomes part of the cell membrane

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55
Q

What must the virus have to use the fusion method

A

envelope and fusion proteins on the viral membrane

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56
Q

What is the receptor mediated endocytosis method of internalization

A

virus binds to a receptor, coated pit forms in cell membrane, inversion of the pit allows it to enter cytoplasm

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57
Q

What method of internalization is most common

A

receptor mediated endocytosis

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58
Q

Once the virus is internalized, what two necessary events need to occur

A

1-production of viral proteins

2-replication of genome

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59
Q

What is the process of production of viral proteins

A

Transcription and translation (since using the cell’s machinery the process is the same as cell protein making)

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60
Q

What must the virus have in order for viruses to be transcribed and translated

A

5’ cap and 3’ tail

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61
Q

How do RNA positive strand viruses duplicate?

A

genome is used directly as mRNA
must have a cap and tail to be recognized
translated to protein

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62
Q

How specifically are RNA positive strand viruses duplicated and then what occurs afterwards

A

they are duplicated by the whole genome at once and then cut into smaller parts

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63
Q

How do RNA negative strand viruses duplicate?

A

RNA genome is complimentary to mRNA

uses a transcriptase and makes complimentary copy of RNA genome that then can be duplicated

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64
Q

What is transcriptase and where’s it come from

A

virus associated polymerase in which brought along with the virus before it entered host cell

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65
Q

How are RNA retroviruses duplicated (4 steps)

A

1- RNA genome transcribed by reverse transcriptas to make DNA copy of RNA
2- RNA is digested and replaced by DNA (creates double stranded DNA)
3- Integrase integrates DNA into host cell genome
4- DNA is transcribed to mRNA along with host cell genome and mRNA translated to protein

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66
Q

When RNA is replaced by DNA and integrated into host cell DNA, what happens

A

the proviral DNA has become a permanent part of the host cell genome

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67
Q

How is a DNA virus duplicated

A

viral genome is transcribed to mRNA by host cell and mRNA to a protein

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68
Q

Where is a DNA virus duplicated

A

in the nucleus

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69
Q

What is replicase

A

enzyme that synthesizes a complementary RNA strand of RNA genome and forms a double strand of RNA that serves as a template for synthesis of new RNA viral genomes

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70
Q

In positive stranded where does replicase come from

A

is translated directly from genome in the form of an early gene

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71
Q

In negative stranded where does replicase come from

A

carried by a virus as a protein

72
Q

What specifically is needed for DNA replicaiton

A

replication form

73
Q

For DNA virus replication, what makes the process rapid

A

both strands are copied simultaneously

74
Q

What occurs during the step of assembly

A

capsid forms around nucleic acid

75
Q

Where does assembly typically occur

A

cytoplasm or at membrane

76
Q

What are the two methods of release of the virus

A

lytic virus release

enveloped virus release

77
Q

what is lytic virus release

A

cell bursts and viruses released (there is no envelope to the virus)

78
Q

What is enveloped virus release

A

bud from the surface, assemble takes place on the membrane, lipid envelope surrounds new virions

79
Q

What is pathogenicity

A

compares the severity of the disease caused by a different virus

80
Q

what does the prefix patho mean

A

disease

81
Q

what is virulence

A

the severity of the disease caused by the same virus

82
Q

How does a small change affect virulence

A

a small change in the viral genome can cause large changes in the virulence in that it can weaken it or make it stronger

83
Q

What particular aspect of the genome would change the virulence

A

spike protein receptor proteins that cause the initial degree of infection

84
Q

What types of diseases are caused on a cellular level because of a virus (5 things)

A 
1- cell lysis
2-cells fuse together
3-malignancy
4-inclusion bodies
5-triggers immune response to infected cells
85
Q

What is synctia

A

giant multinucleated cells

86
Q

What are the steps for viruses causing disease in the entire body (6 things)

A 
1-invade host
2-replicate
3-overcome defense systems
4-spread to other areas via bloodstream
5-replicate
6-exit from host
87
Q

What are the four main routes for invasion and which are the most common two

A 
1- skin
2-mucous membranes
3-transplant
4-mother to fetus
-mucous membranes are the most likely and second would be skin if there were skin breaks
88
Q

What are three modes of transmission

A

respiratory-sneezing and coughing
GI-fecal and oral
Genital- STDs, homo or hetero

89
Q

What are the two types of infection

A

localized

general

90
Q

What is localized infection

A

infection remains near the site of entry

91
Q

What is general infection

A

infection spreads to 1 or more organs NOT at the site of entry

92
Q

What is the difference in incubation periods for localized vs general

A

incubation period for localized is shorter than general due to the virus not needing to travel

93
Q

What is the problem regarding incubation periods for general viruses

A

hard to pinpoint where and when contracted, hard to contain due to long incubation period

94
Q

What are the steps for general infection (6 steps)

A

1-viruses enter epithelium
2-replicate in epithelium then spread
3-migrate to lymph nodes
4-enter bloodstream (onset of fever and fatigue)
5-enters large organs and replicates
6-enters bloodstream and infects target organ

95
Q

What is viremia

A

virus dumping into bloodstream

96
Q

What are the main target organs and tissues

A

skin, buccal mucous membrane, lung, liver, kidney, CNS

97
Q

What is the response for skin infection

A

skin rash

98
Q

What is the response for buccal mucous membrane infection

A

rash on inside of cheeks and lips

99
Q

How long is a short incubation period

A

less than a week

100
Q

How long is a medium incubation period

A

one to three weeks

101
Q

how long is a long incubation period

A

months

102
Q

how long is an extra long incubation period

A

years

103
Q

Why is it important to know the incubation period

A

diagnosis and tracing outbreaks

104
Q

What is acute virus

A

nearly immediate

105
Q

What is a non persistent virus

A

single episode virus

106
Q

What is a chronic virus

A

continually being produced

107
Q

What is persistent virus

A

recurring infection due to latency

108
Q

What is acute onset virus

A

primary infection has symptoms

109
Q

What is reproduction number

A

the average number of secondary cases caused by a single primary case

110
Q

What is the reproduction number not to be confused with

A

severity of virus

111
Q

What are the three mechanisms in order to fight infection

A
  1. barrier to infection
  2. innate immune system
  3. adaptive immune system
112
Q

What is the first line to defense against infection

A

barriers to infection

113
Q

What are examples of barriers to infection

A

skin, cilia, pH in stomach

114
Q

What is meant by species resistance

A

not all viruses infect all species

115
Q

What is innate immunity

A

quick response with no specificity and no memory

116
Q

What are the 3 components of innate immune system

A
  1. toll like receptors
  2. cytokines
  3. natural killer cells
117
Q

What are the three cytokines

A

interferons, chemokines, interleukins

118
Q

When was toll like receptors discovered

A

1997 in humans

119
Q

How many TLRs have been identified

A

12

120
Q

How did TLRs get there name

A

sequence similarity to the toll gene in Drosophila

121
Q

Where are TLRs located

A

on the cell surface or inside cell

122
Q

Are TLRs specific or general

A

general

123
Q

How do TLRs when to activate work

A

when they recognize viral features such as protein spikes, double stranded RNA

124
Q

What are interferons (3 things)

A

a category of cytokines, small proteins, several different types

125
Q

What produces and secretes interferons

A

virus infected cells

126
Q

What is the ultimate goal of interferons

A

to protect neighboring cells from infection

127
Q

Are interferons specific or general

A

not virus specifc

128
Q

What are interferons specific in

A

species specific

129
Q

Basic mechanism of interferons (6 steps)

A
  1. virus binds to Toll like receptor
  2. cell is stimulated to express IFNs
  3. IFNs diffuse out of cell and bind to receptors on neighboring cells
  4. activate enzymes that degrade RNA and stop protein synthesis
  5. activate natural killer cells
  6. enhances adaptive immune response
130
Q

What is the function of natural killer cells

A

recognize and kill infected cells after the cells have been infected

131
Q

Why don’t natural killer cells kill the virus and pathogen

A

because they are not specific to pathogens and only recognize cells

132
Q

What is meant that cells are recognized as “misisng self”

A

low levels of MHC

133
Q

What does MHC do

A

displays the antigens

134
Q

What is the third step of immunity

A

adaptive immune system

135
Q

Features of the adaptive immune system response

A

slow, has memory, controlled by phagocytic cells and lymphocytes

136
Q

2 family types of cells involved in adaptive immune response

A

phagocytic

lymphocytes

137
Q

What are the two cells of the phagocytic cells

A

dendritic, macrophages

138
Q

What are the two cells of the lymphocytes

A

b cell

t cells

139
Q

what are the two types of b cells

A

plasma b cells

memory b cells

140
Q

What are the two types of t cells

A

helper t cells

cytotoxic t cells

141
Q

What is the function of phagocytic cells

A

engulf cells or particles recognized as non self and chew up and display those parts on the surface

142
Q

What are cells presenting the antigen called

A

antigen presenting cells (APC)

143
Q

Where do t cells mature

A

thymus

144
Q

Where do b cells mature

A

bone marrow

145
Q

What is the humoral immunity response

A

antibody mediated

activation of b cells

146
Q

What function do b cells have

A

produce a very specific type of antibody that will recognize a very specific antigen

147
Q

What causes b cells to reproduce and form an entire population

A

stimulation from helper t cell

148
Q

What is the main function of plasma b cells

A

to secrete and release large number of particular antibody into the bloodstream

149
Q

What are the two types of antibodies

A

IgM and IgG

150
Q

What are IgM antibodies

A 
first to be produced
large multi subunits
DO NOT cross into placenta
sign of recent infection
first time infection
151
Q

What are IgG antibodies

A

indication of previous infection
longer lasting
cross placenta to fetus
produced in mothers milk

152
Q

What is the role of memory b cells

A

not used in defense of first infection, prepared for second infection (RAPID response)

153
Q

What do antibodies do

A

bind to the virus and aggregates them to stop attachment to receptors

154
Q

What are helper t cells function

A

to recognize and bind to APC that are displaying antigens, stimulates T cell to produce interleukins which stimulate proliferation of B cells and cytotoxic t cells

155
Q

What is the function of cytotoxic t cells

A

travel through the blood stream recognizing and killing any cells that have the particular antigen on them

156
Q

What are the two types of vaccines

A

active immunization

passive immunization

157
Q

What is active immunization

A

antigen is injected into the body to start a response, causes body to produce plasma and memory b cells

158
Q

What is passive immunization

A

antibodies are injected into a patient to help them fight a current infection

159
Q

What is epidemiology

A

the study of how diseases affect a community

160
Q

What are the 4 major activities for epidemiology

A
  1. predict disease trends
  2. guide control measures
  3. evaluate success of control measures
  4. aid in diagnosis
161
Q

What is seriological epidemiology

A

study of the presence of antibodies in the people of a community

162
Q

What is the iceberg concept

A

antibodies are found in MUCH higher proportion of people than diagnosed with a disease (exposed vs diagnosed)

163
Q

Where is epidemiological info

A

worldwide: WHO
US: CDC

164
Q

2 methods of viral spread

A

Person to person

external source

165
Q

3 factors that determine spread of a virus

A

1- characteristics of a virus
2- characteristics of host
3 characteristics of environment

166
Q

5 characteristics of virus

A 
1- how virus survives outside host
2- virus have alternative host
3-pathogenesis
4- evasiveness of immune system
5- route by which virus is shed
167
Q

Examples of characteristics of the host

A

age, sex, ethnic group, occupation, nutrition, immunity

168
Q

Characteristics of the environment

A

geographic location
urban/rural
existence of vectors
socioeconomic status

169
Q

What is prevalence

A

the proportion of population affected by a disease at a certain POINT

170
Q

What is Incidence

A

the number of cases of a particular disease recorded over a PERIOD of time

171
Q

What is endemic

A

refers to a disease that is constantly present at a significant level

172
Q

What is epidemic

A

an unusual increase in the number of cases within a community “outbreak”

173
Q

What is pandemic

A

an epidemic involving several continents at the same time

174
Q

What is herd immunity

A

proportion of people in a population that are immune to a particular virus

175
Q

Two methods to controlling infections

A

individual and community

Virology (2 decks)

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