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Microbiology LECTURE > Chapter 13 > Flashcards

Chapter 13 Flashcards

Viruses

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1
Q

What are distinctive features of viruses

A
  1. Contain a single type of nucleic acid either DNA or RNA
  2. Contain a protein coat that surrounds the nucleate acid
  3. Multiply inside living cells by using the synthesizing machinery of the cell
  4. Causes the synthesis of specialized structures that can transfer the viral nucleic acid to other cells.
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2
Q

The protein coat of a virus that surrounds the nucleic acid sometimes is enclosed by

A

an envelope made up of lipids, proteins and carbohydrates

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3
Q

How were viruses originaly distinguished from other infectious agents

A

They are especially small in size, filterable, and they are obligatory intracellular cellular parasites

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4
Q

Do viruses generate their own metabolism

A

Viruses have few or no enzymes of their own for metabolism, they lack enzymes for protein synthesis and ATP generation

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5
Q

How do viruses multiply

A

To multiply viruses take over the metabolic machinery of the host cell

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6
Q

Host range

A

The host range of a virus is the spectrum or variety of host cells the virus can infect.

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7
Q

What are examples of the host range of viruses

A

Some viruses can infect invertebrates, vertebrates, plants, protists, fungi, and bacteria. Most viruses infect specific type of cells of only host species. Rarely, viruses cross the host-range barrier.

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8
Q

Bacteriophages

A

Aka phages. Viruses that infect bacteria.

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9
Q

What is required for the virus to infect a host cell

A

For the virus to infect a host cell, the outer surface of the virus must chemically interact with specific receptor sites on the surface of the host cell.

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10
Q

Where are receptor sites on host cells

A

It can be part of the cell wall of the host, it can be part of the fimbriae or flagella, for animal viruses the receptor sites are on the plasma membrane of the host cells

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11
Q

Virus size range

A

20 to 1000 nm in length

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12
Q

Virion

A

A complete, fully developed, infectious viral particle composed of nucleic acid, and surrounded by a protein coat, and is a vehicle of transmission from one host cell to another.

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13
Q

How are viruses classified

A

Based on their nucleic acid and by differences in the structures of their coats

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14
Q

Describe the nucleic acid of a virus

A

It has either DNA or RNA, never both. The nucleic acid can be single stranded or double stranded. It can be linear, or circular, or in several separate segments.

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15
Q

Capsid

A

A protein coat that protects the nucleic acid of a virus. It accounts for most of the mass of a virus.

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16
Q

What determines the structure of the capsid

A

The nucleic acid

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17
Q

Capsomeres

A

Protein subunits that compose the capsid. The protein subunits are of a single type or can be made of several types of protein.

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18
Q

How do capsomeres help identify a virus

A

Their arrangement is characteristic of a particular type of virus

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19
Q

Envelope

A

Some viruses have this, which covers the capsid and is usually made up of a combination of lipids, proteins, and carbohydrates

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20
Q

Animal viruses released from the host cell by an extrusion process have an envelope that is made up of

A

The extrusion process coats the virus with a layer of the host cell’s plasma membrane, that layer becomes the viral envelope. In some cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from the normal host cell components .

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21
Q

Sometimes the envelopes are covered by

A

Spikes made up of carbohydrate-protein complexes (glycoprotein) that project from the surface of the envelope.

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22
Q

How are spikes beneficial to viruses

A

They allow viruses to attach to host cells

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23
Q

What advantages do spikes have for identification of a virus

A

They can cause viruses to bind to RBCs and form bridges resulting in clumping. This is the basis for several useful laboratory tests.

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24
Q

Hemagglutination

A

The clumping of red blood cells.

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25
Q

What would you call viruses whose capsids are not covered by an envelope

A

Nonenvelope viruses (naked virus)

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26
Q

How is a nonenveloped virus protected

A

The capsid protects the nucleic acid from nuclease enzymes in biological fluids and promotes the virus’s attachment to susceptible host cells.

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27
Q

How is it that some viruses can escape antibodies and prevent their inactivation

A

This is due to regions of the genes that code for these virus’s surface proteins that are susceptible to mutations. Their progeny have altered surface proteins and antibodies are not able to react with them.

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28
Q

What are general morphology types of a virus

A
  1. Helical
  2. Polyhedral
  3. Enveloped
  4. Complex
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29
Q

Helical viruses

A

Long rods that may be rigid or flexible, nucleic acid is found within a hollow cylindrical capsid that has a helical structure

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30
Q

Example of helical virus

A

Rabies and ebola haemorrhagic fever

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31
Q

Polyhedral virus

A

Many sided shape, an icosahedron, a regular polyhedron with 20 triangular faces and 12 corners. The capsomeres of each face form an equilateral triangle

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32
Q

Example of polyhedral virus

A

Adenovirus and poliovirus

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33
Q

Enveloped virus

A

Roughly spherical. Helical or polyhedral.

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34
Q

Examples of enveloped viruses

A

Envelope polyhedral–> herpes simplex virus

Enveloped helical–> influenza virus

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35
Q

Complex viruses

A

Some viruses, particularly bacterial viruses have complicated structures.

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36
Q

Example of a complex virus structure

A

Bacteriophage. Some have capsids to which additional structures are attached. Capsid head is polyhedral and the tail sheath is helical. Head contains the nucleic acid.

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37
Q

Example of a complex virus

A

Poxviruses

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38
Q

The International Committee on Taxonomy of Viruses groups viruses into families based on

A

Genomics and structure with the help of DNA sequencing

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39
Q

What suffix is used for genus names

A

-virus

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40
Q

Family names end in

A

-viridae

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41
Q

Order names end in

A

-ales

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42
Q

In formal usage, in what order are family and genus, viral species, and subspecies names used, example

A

FAMILY–> Herpeaviridae,
GENUS–> Simplexvirus,
Viral species–> human herpesvirus
Subspecies–> 2

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43
Q

Viral species

A

A group of viruses sharing the same genetic information and ecological niche (host range). Common names are used for species.

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44
Q

Subspecies

A

Different strains are designated by a number.

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45
Q

Spikes are

A

Also called peplomeres. They are made up of glycoproteins; proteins linked to sugars known as hemagglutinin (HA) and neuramidase (NA).

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46
Q

Where has much of our understanding about viruses come from

A

Bacteriophages, viruses that use bacteria as a host.

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47
Q

Where can bacteriophage be grown in the lab

A

Suspensions of bacteria in liquid media or in bacterial cultures on solid media.

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48
Q

What is made possible by growing bacteriophages on solid media

A

The plaque method for detecting and counting viruses

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49
Q

How would you perform the plaque method

A

A sample of bacteriophage is mixed with host bacteria and melted agar. This is then poured into a petri plate containing a hardened layer of agar growth medium. The mixture solidifies into a thin top layer that contains a layer of bacteria approximately one cell thick.

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50
Q

How do plaques form

A

Each virus infects a bacterium, multiplies, releases several new viruses that infect other bacteria in the immediate vicinity. After several viral multiplication cycles all the bacteria surrounding the original virus or destroyed. This produces a number of clearing or plaques visible against a lawn of bacterial growth on the surface of the agar.

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51
Q

Each plaque corresponds to

A

A single virus in the initial suspension

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52
Q

PFU

A

Plaque forming units, the concentration of viral suspension measured by the number of plaques

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53
Q

The most important taxonomic criteria are

A
  1. Host organism
  2. Particle morphology
  3. Genome type
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54
Q

Nucleic acid classification

A
  1. RNA viruses; single stranded or double stranded

2. DNA viruses; single stranded or double stranded

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55
Q

Subcategories of RNA viruses

A
  1. Positive strand
  2. Negative strand
  3. Retrovirus
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56
Q

Animal inoculation with a virus is used as a

A

Diagnostic procedure for identifying and isolating a virus in the clinical specimen. The animal is observed for signs of disease or is killed for examination of infected tissues

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57
Q

Can all human viruses be grown in animals

A

No because they do not all cause the disease or symptoms of the disease in animals. They cannot be used to study the effects of viral growth and disease treatments.

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58
Q

What is a convenient and inexpensive form of growing animal viruses

A

Inoculation of an embryonated egg

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59
Q

How is an embryoated egg inoculated

A

A hole is drilled in the shell of the egg and a viral suspension or suspected virus containing tissue is injected into the fluid of the egg

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60
Q

How do you know viral growth has occurred in an embryo

A
  1. Death of an embryo
  2. Embryo cell damage
  3. Formation of typical pocks of lesions on the egg membranes
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61
Q

What is the embryo method used mostly for today

A

Viral vaccine preparation

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62
Q

What are the different membranes in an egg that the virus can be injected into

A
  1. Chorioallantoic membrane
  2. Amniotic membrane
  3. Allantoic membrane
  4. Yolks sac
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63
Q

What type of viral culture has replaced embryonated eggs

A

Cell cultures

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64
Q

What do cell cultures consist of

A

Cells from animal tissues grown in a culture medium

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65
Q

What are cells from cell cultures suspended in

A

They are suspended in a solution that provides the osmotic pressure, nutrients, and growth factors needed for the cells to grow

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66
Q

How are cell culture lines prepared

A

A slice of animal tissue is treated with enzymes that separates the individual cells

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67
Q

What are the 3 basic types of cell cultures widely used in clinical and research virology

A
  1. Primary cell cultures
  2. Diploid fibroblast strains
  3. Continuous cell lines
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68
Q

How do normal cells in a cell culture grow

A

They tend to adhere to the glass or plastic container and reproduced to form a monolayer. They have a type of on/off switch for growth.

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69
Q

Cytopathic effect (CPE)

A

The visible effect viruses have on cells

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70
Q

How is CPE counted

A

In the same way as plaques in a lawn of bacteria and are reported as PFU per ML

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71
Q

Primary cell cultures

A

Come directly from animal tissue slices, and if repeatedly subcultured, one cell type will become dominant (cell strain)

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72
Q

What is a disadvantage of primary cell cultures

A

They don’t last long and tend to die off after only a few generations

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73
Q

Diploid fibroblast strains

A

Most widely used strain and support growth of a wide range of viruses that require a human host. They are developed from human embryos and can be maintained for about a 100 generations.

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74
Q

Continuous cell lines

A

This is used when viruses are routinely grown in a lab. These are transformed cancerous cells that can be maintained through an indefinite number of generations

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75
Q

Continuous cell lines are sometimes called

A

Immortal cell lines

76
Q

What is one of the most famous continuous cell lines

A

HeLa cell line. It was isolated from the cancer of a woman, Henrietta Lacks who died in 1951.

77
Q

How do transformed cells from a cell line grow

A

These are continuous cell cultures that do not grow in a monolayer. They do not have an on/off switch to stop growth.

78
Q

What’s an example of a cytopathic effect

A

The cell deterioration by a virus infecting a monolayer of normal cells as they attempt to multiply

79
Q

What are the common cytopathic effects in a viral cell culture

A

Changes in cell shape and detachment from adjacent cells or culture container

80
Q

An experienced Virologist can use CPE to

A

To make a preliminary ID of the infecting virus

81
Q

Syncytia

A

Giant multinucleate cells caused by fusion of adjacent cells

82
Q

What are methods used to identify a virus

A
  1. Evaluating cytopathic effects
  2. Seroloical tests
  3. Evaluating nucleic acids
83
Q

What is the most common selogical method for identifying viruses

A

Western blotting

84
Q

What do Serological tests for viral identification look for

A
  • Detect antibodies against viruses in a patient

* Use antibodies to identify viruses in neutralization tests, viral hemagglutination and Western blot

85
Q

What viral identification methods include nucleic acids

A

▪︎Restriction fragment length polymorphism (RFLP)

▪︎ Polymerase chain reaction (PCR)

86
Q

What instrument is used to visualize and identify viruses

A

An electron microscope

87
Q

What is PCR used for

A

To amplify viral RNA, to identify a virus

88
Q

What is provided by a host cell once a virus has infected it

A

Enzymes needed for protein synthesis, ribosomes, tRNA, and energy production, are used for synthesizing viral proteins

89
Q

What are the 2 mechanisms by which bacteriophages can multiply

A
  1. Lytic cycle

2. Lysogenic cycle

90
Q

The lytic cycle ends with

A

Lysis and death of the host cell

91
Q

The lysogenic cycle is different from the lytic cycle in that the host cell

A

Remains alive

92
Q

Stages of multiplication in lytic cycle

A
  1. Attachment
  2. Penetration
  3. Biosynthesis
  4. Maturation
  5. Release
93
Q

Virions of T-even bacteriophages

A

Large and complex, nonenveloped, characteristic head and tail structure,

94
Q

Attachment

A

Tail fibers attach to cell wall proteins. An attachment site on the virus attaches to a complimentary receptor site on the bacterial cell. A chemical interaction takes place in which weak bonds are formed

95
Q

Penetration

A

After attachment. The T-even bacteriophage injects its DNA (nucleic acid) into the bacterium.

96
Q

Describe the penetration process

A

The bacteriophage’s tail releases an enzyme, phage lysozyme, which breaks down part of the bacterial cell wall. During penetration, the tail sheath contracts to force tail core into the cell wall until the tip reaches the plasma membrane, and the DNA is inserted in the host cell.

97
Q

Biosynthesis

A

The bio synthesis of viral nucleic acid and protein occurs.

98
Q

How does the phage attach to host cell

A

It attaches by tail fibers to host cell

99
Q

Genetic controls regulate when …

A

Different regions of phage dna are transcribed into mRNA during the multiplication cycle

100
Q

Eclipse period

A

Takes place during biosynthesis. The period during viral multiplication when complete and infective virions are not yet present. Only separate components, DNA and protein can be detected.

101
Q

Maturation

A

Viral components: bacteriophage DNA and capsids, are assembled into complete virions. This occurs spontaneously. The phage heads and tails or separately assembled from protein subunits, the head is filled with phage DNA and attached to the tail.

102
Q

Release

A

The final stage. The plasma membrane breaks open which is caused by lysozyme produced within the host cell, encoded by a phage gene. Virions are released from the host cell and bacteriophages infect other susceptible cells in the vicinity.

103
Q

Lysogenic phages are also called

A

Temperate phages

104
Q

Lysogeny

A

A type of life cycle where a bacterial phage infects a type of bacterial host cell and can remain latent or inactive

105
Q

Participating bacterial hosts cells infected by a lysogenic phage are called

A

Lysogenic cells

106
Q

What is a well studied lysogenic phage

A

Lambda

107
Q

Describe the lysogenic cycle

A
  1. Upon penetration into an E. coli cell, the originally linear phage dna forms a circle.
  2. Instead of multiplying and being transcribed it enters the lysogenic cycle. The DNA circle recombines with and becomes part of the circular bacterial DNA. The prophage remains latent.
  3. Every time the host cell’s machinery replicates the bacterial chromosome also replicates the prophage dna.
  4. A spontaneous event can lead to the excision of the phage dna and initiate the lytic cycle
108
Q

What events can bring a lysogenic phage out of its latent stage

A

The action of UV light, certain chemicals

109
Q

The inserted phage DNA is called

A

A prophage

110
Q

How are prophage genes repressed

A

Most are repressed by 2 repressor proteins that are the products of phage genes. These repressors stop transcription of all the other phage genes by binding to operators. The phage genes that would otherwise direct the synthesis and release of new virions are turned off.

111
Q

What are the 3 important results of lysogeny

A
  1. Lysogenic cells are immune to reinfection by the same phage, but not to other types
  2. Phage conversion
  3. It makes specialized transduction possible
112
Q

Phage conversion

A

The host cell may exhibit new properties

113
Q

What is an example of phage conversion

A

Corynebacterium diphtheriae’s disease producing properties are related to the synthesis of a toxin. It can only produce this toxin when it carries a lysogenic phage because the prophage carries the gene coding for the toxin.

114
Q

Specialized transduction

A

When a prophage is excised from the host chromosome, adjacent genes from either side may remain attached to the phage dna. The lysogenic phage packages bacterial DNA along with it’s own DNA in the same capsid after lysing of the cell. Once the phage infects a new host, the prophage along with the new bacterial genes become integrated into the new host’s DNA.

115
Q

What happens to viruses that infect animals and remain latent in cells for long periods without multiplying and causing disease

A

The virus can be inserted into a host chromosome or remain separate from the host DNA in a repressed state

116
Q

Multiplication of animal viruses stages

A
  1. Attachment
  2. Entry
  3. Uncoating
  4. Biosynthesis or chronic infection and then biosynthesis
  5. Maturation and Release
117
Q

What are the differences in animals viruses when compared to bacteriophages

A

▪︎Mechanism have entering the host cell
▪︎The synthesis and assembly of the new viral components
▪︎They have different enzymes than those found in phages
▪︎ The mechanism of maturation and release
▪︎ The effects on the host cell

118
Q

Animal virus attachment

A

Animal viruses have attachments sites that attached to complimentary receptor sites on the host cell’s surface. Receptor sites of animal cells are proteins and glycoproteins of the plasma membrane. The attachment sites for distributed over the surface of the virus and vary from one group to another.

119
Q

When is attachment of animal viruses complete

A

When many sites are bound

120
Q

Entry of animal viruses

A

Entry occurs by receptor mediated endocytosis or fusion

121
Q

Receptor mediated endocytosis

A

If a virion attaches to the plasma membrane of a potential host, the host cell will enfold the virion into a fold of plasma membrane forming a vesicle and bringing it into the host cell.

122
Q

Fusion

A

Enveloped viruses can enter by this alternative method. The viral envelope fuses with the plasma membrane and releases the capsid into the cell’s cytoplasm.

123
Q

Uncoating

A

The enzymatic separation of the viral nucleic acid from its protein coat occurs once the virion is enclosed within the vesicle. Nonenveloped capsid may be released into the cytoplasm of the host cell

124
Q

What enzymes are used for uncoated animal viruses

A
  • Some use lysosomal enzymes other of the host cell

* Others are specific enzymes encoded by viral DNA

125
Q

Biosynthesis of animal DNA viruses

A

The DNA of most DNA viruses is released into the nucleus of the host cell. Transcription of viral DNA and translation produce viral DNA and, later capsid proteins. Capsid proteins are synthesized in the cytoplasm of the host cell.

126
Q

When does maturation of a DNA virus happen

A

This happens after the capsid proteins migrate into the nucleus of the host cell. The viral DNA and capsid protein assemble to form complete viruses. They are then released from the host cell.

127
Q

In most DNA by viruses early transcription is carried out with

A

The hosts transcriptase (RNA polymerase)

128
Q

Why do viruses disappear during the eclipse period of an infection

A

Because they are taken apart inside the host cell

129
Q

RNA virus biosynthesis

A

This occurs in the host cell’s cytoplasm. Different mechanisms of mRNA formation occur among different groups of RNA viruses. After viral RNA and viral proteins are synthesized maturation occurs.

130
Q

What occurs after the uncoating if a ssRNA, sense strand (+strand)

A

The RNA strand within the virion, acts as mRNA. , the single stranded viral RNA is translated into 2 principal proteins, which inhibit the host cells synthesis of RNA and protein and which form an enzyme called RNA dependent RNA polymerase.

131
Q

What does the enzyme RNA dependent RNA polymerase catalyze

A

The synthesis of another strand of RNA which is complementary in base sequence to the original infecting strand

132
Q

The new strand catalyzed by RNA dependent RNA polymerase is called

A

Antisense strand or - strand

133
Q

What does the antisense strand do

A

It serves as a template to produce additional .+ strands. These strands serve as

  1. mRNA for the translation of capsid proteins.
  2. May become incorporated into capsid proteins to form a new virus
  3. May serve as a template for continued RNA multiplication
134
Q

What are the 3 pathways of RNA virus synthesis

A
  1. ssRNA, +strand
  2. ssRNA, -strand
  3. dsRNA, +strand with -strand
135
Q

Uncoating releases

A

Viral RNA (genome) and viral proteins

136
Q

ssRNA virus with a - strand

A

These viruses must transcribe a + strand to serve as mRNA before the begin synthesizing proteins. The mRNA transcribes additional - strands for incorporation into capsid protein

137
Q

dsRNA, +sense with - strand

A

mRNA is produced inside the capsid and released into the cytoplasm of the host. RNA polymerase initiates production of antisense strands. The mRNA and antisense strands form DNA that is incorporated as new viral genome

138
Q

Togaviridae biosynthesis

A

+ strand of RNA; after - strand is made from + strand, 2 types of mRNA are transcribed from the - strand. One type of mRNA is a short strand that codes for envelope proteins, the longer strand serves as mRNA for capsid proteins and can become incorporated into a capsid

139
Q

Multiplication of RNA viruses occurs in the

A

Cytoplasm of the host cell

140
Q

RNA dependent RNA polymerase synthesizes

A

Double stranded RNA

141
Q

Biosynthesis of retroviruses

A

These viruses carry reverse transcriptase, which uses viral RNA as a template to produce complementary double stranded DNA. The enzyme also degrades the original viral RNA. The viral DNA is then integrated into a host cell chromosome as a provirus.

142
Q

What happens to the provirus

A

Sometimes the provirus remains in a latent state and replicates when the DNA of the host cell replicates. Other times it is expressed and produces new viruses which can infect adjacent cells.

143
Q

What can induce expression of a provirus

A

Mutagens such as gamma radiation

144
Q

What happens during transcription of a provirus

A

Transcription produces RNA for a for new retrovirus genome and RNA that encodes the retrovirus, capsid, enzymes, and envelope proteins

145
Q

After transcription of the provirus, viral proteins are processed by

A

Viral protease

146
Q

What does a mature retrovirus acquire when it leaves the host cell

A

An envelope and attachments spikes as it buds out

147
Q

How does a retrovirus enter a host cell

A

By fusion between attachments spikes and the host cell receptor

148
Q

What is the 1st step in viral maturation of an animal virus

A

The assembly of the protein capsid.

149
Q

What are the capsids of many animal viruses enclosed by

A

Envelopes made up of protein, lipid, and carbohydrate

150
Q

What encodes envelope proteins

A

Viral genes and are incorporated into the plasma membrane of the host cell

151
Q

What encodes the lipids and carbohydrate of an envelope

A

Host cell genes and are present in the plasma membrane

152
Q

How does the envelope develop

A

Around the capsid by a process called budding

153
Q

What part of the host cell becomes part of the envelope

A

A portion of the plasma membrane adheres to the virus and becomes part of the envelope

154
Q

How are animal viruses released from the host cell

A

▪︎Enveloped visues are released by budding

▪︎Nonenveloped viruses are released through ruptures in the host cell plasma membrane–>causing death of hist cell

155
Q

Several types of cancer known to be caused by

A

Viruses

156
Q

What are reasons that cancers caused by a virus go unrecognized

A
  1. Most of the particles of some viruses infect cells but do not induce cancer
  2. Cancer might not develop until long after viral infection
  3. Cancers do not seem to be contagious as viral diseases are
157
Q

Oncogenes

A

Parts of the genome affected by cancer causing alterations to cellular DNA

158
Q

What has the potential to make a normal cell cancerous in a eukaryotic cell

A

Anything that can alter the genetic material

159
Q

How are ocogenes activated to abnormal functioning

A

Mutagenic chemicals, high energy radiation, and viruses

160
Q

Oncogenic viruses

A

Viruses capable of inducing tumors in animals

161
Q

How our oncogenic viruses similar to lysogeny in bacteria

A

Their genetic material integrates into the host cell DNA and replicates along with the host cell’s chromosome.

162
Q

What happens when tumor cells undergo transformation

A

They acquire properties that are distinct from the properties of uninfected cells or from infected cells that do not form tumors

163
Q

What is the virus specific antigen on the cell surface of a cell transformed tumor cell called

A

Tumor specific transplantation antigen (TSTA)

164
Q

T antigen

A

An antigen in the nucleus of a transformed tumor cell

165
Q

Activated oncogenes transform normal cells into

A

Cancerous cells

166
Q

What are the hallmarks of transformed cells

A
  1. They have increased growth
  2. They have loss of contact inhibition
  3. TSTA or T antigens
167
Q

The genetic material of oncogenic viruses become integrated into

A

the host cell’s DNA

168
Q

What kind of viruses become ocogenic

A

DNA viruses and Retroviruses (RNA virus)

169
Q

How can retroviruses induce tumors

A

This is related to their production of a reverse transcriptase . The provirus which is the double stranded DNA molecule synthesized from the viral RNA, becomes integrated into the host cell’s DNA, new genetic material is thereby introduced into the host genome, and this is a key reason retroviruses can contribute to cancer.

170
Q

What do retroviruses contain that turn on oncogenes or other cancer causing factors

A

Ocogenes or Promoters

171
Q

Proteins produced by tumor viruses can cause

A

uncontrolled host cell division.

172
Q

Proto-oncogene

A

A normal gene, that when under the control of a virus, can cause uncontrolled cell division and can act as an oncogene

173
Q

How do oncogenes work

A
  1. Product of oncogene can disrupt normal cell function leading to uncontrolled cell divisions
  2. Controlled by viral regulators near the site of their integration into the host cell’s chromosomes
174
Q

Teratogenesis

A

The induction of defects during embryonic development

175
Q

Teratogen

A

A drug or other agent that induces birth defects

176
Q

What 3 human viruses account for a large number of teratogenic affects

A
  1. Cytomegalovirus
  2. HSV 1 and 2
  3. Rubella
177
Q

What type of infections are those caused by ocogenic viruses

A

Latent infections

178
Q

Latent infection

A

The virus inhabits the host cells but causes no damage until it is activated by a stimulus. Viruses remain asymptomatic until they suddenly appear.

179
Q

Persistent or chronic viral infection

A

Occurs gradually over a long period. These are detectable infectious viruses that gradually build up over long periods. Typically persistent viral infections are fatal.

180
Q

Prion

A

Proteinaceous infectious particle, a mutated protein. Infection is inherited and transmissible by ingestion, transplant, and surgical instruments.

181
Q

PrPc

A

Normal cellular prion protein on cell surface

182
Q

PrPsc

A

Scrapie protein; accumulates in brain cells, forming plaques

183
Q

How can a protein become infectious

A

If an abnormal prion protein enters a cell, it changes a normal prion protein to an abno6prion protein, which now can change another normal prion protein, resulting in an accumulation of the abnormal prion proteins

184
Q

How do plant viruses enter plants

A

Through wounds or via insects

185
Q

Viroids

A

Short pieces of naked RNA, only 300 to 400 nucleotides long, with no protein coat. They cause plant diseases.

Microbiology LECTURE (13 decks)

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