1
Q
What is a virus?
A
An obligate, intracellular parasite that’s sub-microscopic and has a specific range of hosts.
2
Q
What kind of parasites are viruses?
A
Obligate, intracellular parasites - they cannot grow or produce energy on their own! They NEED a host to replicate and pass their genetic information on
3
Q
What do simple viruses consist of?
A
Only genetic material (RNA or DNA) and a capsid
4
Q
Viruses are ______-microscopic. What does that mean?
A
Sub-microscopic, meaning that they are too small to be seen with a light microscope and can only be seen with electron microscope
5
Q
Viruses are ____-specifc and ______-specific.
A
Host, tissue
6
Q
What is a group of viruses that exclusively attacks bacteria?
A
Bacteriophages
7
Q
What does a virus’s specificity derive from?
A
Derives from the interactions with specific cell-surface receptors. This is why there are different versions of the flu - avian flu, swine flu, and human flu.
8
Q
Why are viruses called agents rather than organisms?
A
Because they are acellular and non-living
9
Q
What two elements does every virus have?
A
1) Nucleic acid (DNA or RNA, either single-stranded or double-stranded)
2) Capsid
10
Q
Every virus must have ___________________. Some viruses (but not all) have ________________.
A
Nucleic acid and a capsid, envelopes and spikes
11
Q
What is a capsid?
A
The outer protein cover that protects the virus’s genetic material
12
Q
What are capsids made of?
A
Basic protein subunits called capsomeres that automatically self-assemble around the nucleic acid
13
Q
What protects the virus’s nucleic acids from physical or chemical damage?
A
The capsid
14
Q
What determines the virus’s shape?
A
Capsid
15
Q
Viruses have a number of shapes, but which one is the most distinctive shape unique to viruses?
A
Icosahedron shape = a polyhedron with 20 triangular faces, 30 edges, and 12 vertices
16
Q
What are the important functions of the capsid for viruses?
A
1) Protecting the nucleic acid
2) Interacting with receptors on the surface of the host cell
3) Facilitating the penetration of the nucleic acid into the cell
17
Q
What is a viral envelope and its function?
A
- A structure that’s composed of lipids and proteins that derive from the host’s cell membrane or internal membranes.
- It helps a virus enter hosts cells
18
Q
What is a spike and its function? Where can they be present?
A
- Spike = a protein found in the viral envelope
- They assist in the recognition and attachment to the host cell
- They can be present on either RNA or DNA viruses
19
Q
What characteristics are viruses categorized by?
A
1) Type of host they infect - animal viruses, plant viruses, etc.
2) Nucleic acid content - RNA or DNA, single-stranded or double-stranded
3) Envelope or no envelope
4) Type of infection
20
Q
What are enveloped viruses?
A
Viruses that contain an envelope
21
Q
What are naked viruses?
A
Viruses that do not contain a envelope
22
Q
What are the major steps in viral replication?
A
1) Attachment/adsorption
2) Entry/penetration
3) Uncoating (if a capsid penetrates the host)
4) Synthesis/replication
5) Assembly
6) Release
23
Q
What is a common mechanism of viral attachment and entry?
A
Receptor-mediated endocytosis
24
Q
What do viruses use to attack to specific receptors on the host cell?
A
Capsids or spikes on the viral envelope
25
What is a virion?
A virus that's found outside a host cell
26
How do naked viruses attach?
By releasing their nucleic acids directly into the cell by injecting it
27
What happens during the entry/penetration phase?
The virus injects its genetic information into the host cell.
28
What is lost upon entry into the host cell?
The viral envelope (if present)
29
What happens during the synthesis/replication phase?
The viral genome is replicated and capsid proteins are produced
30
True or False: Different viruses have different strategies for replication.
True
31
What is the strategy of replication for single-stranded DNA viruses?
They use host enzymes to make a complementary strand, which is replicated and transcribed normally using the host's enzymes.
32
What is the strategy of replication for double-stranded DNA viruses?
By using the host's enzymes
33
What is the strategy of replication for positive-sense, single-stranded RNA viruses?
They have genomes that can act directly as mRNA and carry a unique viral protein that makes a complementary, negative-sense strand.
34
What is the strategy of replication for negative-sense, single-stranded RNA viruses?
They have a genome that must be copied into a positive-sense strand before it can act as messenger RNA.
35
What is the strategy of replication for double-stranded RNA viruses?
It uses a host's enzyme to make proteins (including RNA-dependent RNA polymerase) from the positive-sense strand. That can be used to make more negative-sense strands from a positive-sense template
36
What is the strategy of replication for retroviruses?
They use an RNA-dependent DNA polymerase called reverse transcriptase (RT) to make DNA from RNA.
37
What does it mean when a single-stranded RNA is positive-sense?
It can be used directly as mRNA to make proteins
38
What does it mean when a single-stranded RNA is negative-sense?
It must be replicated into a positive-sense strand before it can be used to make proteins
39
What happens during the assembly stage of viral replication?
Involves the assembly of the protein capsid around the nucleic acid core. This process occurs within the host cell
40
What happens during the release stage in viral replication?
Where replicated viruses are released to the external environment, they become virions again and cause the host cell to lyse, releasing many viruses into the external environment.
41
What is budding?
The release of viruses that occurs slowly
42
What is the release strategy for naked viruses?
Leaves the host cell via lysis
43
What is the release strategy of enveloped viruses?
Leaves the host cell via budding
44
What may viruses acquire after leaving the host during the release stage of viral replication?
Viruses acquire their envelope (if any)
45
What is a retrovirus?
A family of virus that replicates by converting its single-stranded RNA genome to double-stranded DNA and integrating it into the host cell's genome.
46
Retroviruses contain genes that produce a special enzyme called...
reverse transcriptase (RT)
47
What is reverse transcriptase?
An RNA-dependent DNA polymerase that makes double-stranded DNA from a single-stranded RNA template
48
What is the three-step process that reverse transcriptase facilitates?
1) A DNA-RNA hybrid is formed when reverse transcriptase creates a DNA strand that's complementary to the virus's single-stranded RNA
2) The strand of RNA is removed
3) The newly synthesized DNA strand is used as a template for the synthesis of a complementary strand, forming the final, double-stranded molecule.
49
What is an integrase?
An enzyme that integrates the double-stranded DNA into the host chromosome
50
What is a provirus?
Viral DNA after the double-stranded DNA has been integrated into the host's chromosome
51
What is the most infamous retrovirus?
Human immunodeficiency virus (HIV)
52
What is a virus's pathogenicity?
The capacity to cause a disease
53
What mechanisms/abilities are involved in increasing a virus's pathogenicity?
1) The ability to penetrate host cells
2) The ability to grow within the cell
3) The ability to fight against the host cell's defense mechanism
4) The ability to damage the host
54
How can viruses penetrate the body?
1) Through a wound caused by direct trauma
2) Through insect bites
3) Through the mucous membranes (GI tract, urogenital tract, etc)
55
What is the best way viruses can penetrate the body?
Through the mucous membranes
56
How do viruses damage/change their host organisms?
1) Inducing lysis, which kills the cell
2) Inhibiting RNA synthesis or protein synthesis
3) Transforming the cell's genome
57
True or False: Viruses impact an organism by simply just entering the body
FALSE - it has to penetrate the cell membrane of a target cell in order to reproduce and have any impact on the organism
58
What area in the body the most common route of entry for all diseases?
Respiratory tract
59
What are alveolar macrophages?
Important immune system cells that fight infection in teh alveoli
60
How do viruses spread through the body?
1) They can spread over epithelial surfaces
2) Neurotropic viruses spread through cells in the nervous system (EX: rabies)
3) Lymphotropic viruses spread through the lymphatic system (system that brings the liquid that seeps out of blood vessels back to the heart)
4) Spread in the bloodstream (Viremia)
61
How do viruses leave the body?
Through virus shedding, which refers to the many ways that the virus can leave the body
62
What are the different types of viral infections?
1) Lytic infection
2) Persistent infection
3) Latent infection
4) Transforming infection
63
What is a lytic infection?
The "standard" kind of viral infection, in which the virus infects the host, makes more copies of itself, and causes lysis. It's an acute infection (short).
64
In what type of infection can't viruses successfully complete replication?
Abortive or non-productive infection
65
What is a persistent infection?
When viruses reproduce slowly and are released by the cell slowly over a long period of time. They can result in chronic infection that lasts for a long period of time and does not kill the host immediately.
66
What is a latent infection?
A virus that remains in the host cell in a dormant state until a trigger activates it and causes it to make more copies of itself.
67
How are cold sores produced?
They are produced as a result of a latent viral infection.
68
What is a transforming infection?
A virus that affects the host's genetic makeup, causing some kind of mutation in the host chromosome.
69
What is the cytopathic effects (CPE) of a virus?
The effects of a viral infection that can be visualized with a microscope
70
What are some examples of cytopathic effects?
1) The formation of viral plaque, or a visible area where the virus has destroyed infected cells in a cell culture in a Petri dish.
2) The fusion of cells, producing a multinucleate cell called a syncytium.
71
What does the syncytia formation involve?
It involves the creation of a single cell with multiple nuclei
72
How do normal cells look vs infected cells?
- Normal cells look largely symmetrical and healthy looking
- Infected cells are asymmetrical and round
73
What is the one-step growth cycle?
A technique developed by bacteriophage virologists.
74
What does a one-step growth cycle do?
It involves exposing bacteria to viruses, then diluting the sample enough that no additional hosts are infected by new viruses. Viruses can then be measured in the sample.
75
What are the stages in a one-step growth cycle?
1) Attachment & penetration
2) Eclipse
3) Yield/Maturation
4) Release
76
What happens during the attachment & penetration phase in a one-step growing cycle?
The virus binds to receptors on the host's cell membrane and then are brought into the cell via receptor-mediated endocytosis, forming an endosome. The virus then produces compounds that lower the pH inside the endosome, which causes the virus to uncoat and triggers the virus's fusion with the endosome.
77
What does the low pH cause in the attachment phase of the one-step growth cycle?
Causes uncoating and fusion of the virus to an endozome
78
What happens during the eclipse phase of the one-step growing cycle?
No detectable infectious viruses are present, but produces components needed to produce more viruses.
79
What happens during the maturation/yield phase in a one-step growing cycle?
The number of observable infectious viruses in the cell increases as the viruses begin to assemble
80
What phase in the one-step growing cycle is where infectious particles are detected?
During the yield (or burst/rise) period
81
What happens during the release phase in the one-step growing cycle?
The number of viral particles remains high, and eventually, the viruses are liberated from the cell.
82
What is a syndrome?
A collection of signs and symptoms
83
What is a sign?
An objective manifestation of the virus, like a rash, that can be detected by others
84
What is a symptom?
An internal manifestation that can only be detected by the infected individual.
85
List some signs and symptoms of viruses.
1) Oral infections
2) Respiratory tract infections
3) Eye infections
...you get the point
86
What is a lytic cycle?
A type of phage replication cycle resulting in the release of new phages by lysis (and death) of the host cell
87
What is a consequence of the lytic cycle?
The host ultimately dies and new phages are produced
88
What is a lysogenic cycle?
A phage replication cycle where the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host
89
What does lysogeny involve?
Involves the integration of the bacteriophage's nucleic acid into the host's genome.
90
What is a temperate phage?
A phage that's capable of establishing lysogeny and integrating into the bacterial host.
91
What is a lysogen?
A bacterium that contains a virus
92
What is induction?
The process in which the prophage begins to initiate synthesis of new phage particles
93
What are the three mechanisms of horizontal gene transfer?
1) Conjugation
2) Transformation
3) Transduction
94
What is conjugation?
Involves the transfer of genetic material between bacteria through direct contact
95
What is transformation?
Involves the direct uptake of genetic material from a bacterium's surroundings
96
What is transduction?
Involves the transfer of genetic information from one bacterium to another via a virus
97
Where can viruses be cultured in/grown in labs?
Viruses can be cultured in cell culture, in laboratory animals, or in embryonated eggs. Culture media do NOT provide a method of culturing viruses
98
What are some tools used in virus quantification?
1) Plaque assay technique
2) Hemagglutination assay
3) Tissue culture assay technique
99
What is plaque assay technique?
Allows researchers to count the number of viruses in a known volume of a sample
100
What is a hemagglutination assay?
A technique that takes advantage of the fact that hemagglutinin ( a surface protein of influenza viruses) causes red blood cells to agglutinate, or clump up.
101
What is the tissue culture assay technique?
A technique that uses humans or cells rather than bacterial cells
102
________ can cause cancer.
Viruses
103
What is neoplasia?
Any abnormal new cell growth and reproduction due to loss of regulation of the cell type
104
What does neoplasia often lead to?
Leads to the formation of a tumor, typically benign. However, it can become dangerous when they metastasize, or spread throughout the body.
105
What is carcinogenesis?
The complex process where cancer forms that involves cancer-causing genes called oncogenes
106
True or False: There are mechanisms where viruses cause cancer.
FALSE - There is NO single mechanism where viruses cause cancer.
107
What are prions?
Infectious proteins that are linked to a variety of degenerative diseases in humans and animals.
108
What are viroids?
Infectious agents consisting of only closed, single-stranded RNAs.
109
What are some examples of prions?
1) Bovine spongiform encephalopathy (BSE) or mad cows disease
2) Scrapie (in sheep)
3) Creutzfeldt-Jakob disease (in humans)
110
What are prions made of?
PrP proteins
111
What are the two forms of prions?
1) A "normal" form with an alpha-helix structure
2) A "disease-causing" form with a beta-sheet structure
112
________ primarily cause disease in plants.
Viroids
Micriobiology
flashcards
Decks in class (15)
# Cards
-
Module 1 - Intro to Microbiology: Exploring Microbial World114
-
Module 2 - Cell Structure & Function, Microscopy, + Prokaryotes/Eukaryotes51
-
Module 3 - Macromolecules, Cellular Chemistry, Microbial Growth, and Nutrition47
-
Study Guide Example Questions23
-
Exam 2 - Metabolism58
-
Exam 2 - DNA Replication25
-
Exam 2 - Transcription17
-
Exam 2 - Translation1
-
Exam 2 - Regulating Gene Expression0
-
Exam 2 - Mutation and DNA repair0
-
Exam 2 - Into to Genetics15
-
Exam 3 - Genetic Engineering & Biotechnology130
-
Microbial Ecology46
-
Antimicrobial Chemotherapy102
-
Viruses112
