Chapter 13 Flashcards
(66 cards)
1
Q
Virus literally means…
A
Poison
2
Q
Viruses are __________ _________ parasites
A
Obligate, Intracellular
3
Q
How big/small are Viruses?
A
20 – 1000 nm
4
Q
What is the goal of Viruses?
A
To reproduce
5
Q
Why are most organisms susceptible to viral infection?
A
we think viruses are ancient and have been evolving along with organisms
6
Q
Pandora Virus
A
opens Pandora’s box and makes us change the way that we think about viruses and change perspectives of evolutionary biology
7
Q
Bacteria can be filtered to _____________.
A
Sterilize
8
Q
Do Viruses contain DNA, RNA or Both
A
Either DNA or RNA
9
Q
Characteristics
A
- contain a single type of nucleic acid, either DNA or RNA,
- contain a protein coat,
- multiply inside living cells using the cellular machinery
- cause synthesis of specialized structures that transfer viral genetic information.
10
Q
Why are antiviral drugs difficult to develop?
A
target host machinery!
11
Q
Virion
A
complete, fully-developed infectious viral particle
12
Q
How are Viruses classified?
A
- morphology,
- type and structure of genetic information
- replication strategy.
13
Q
Does a Virion contain DNA, RNA or Both?
A
?
14
Q
Viral genetic information is encoded in _________?
A
- double-stranded DNA,
- single-stranded DNA,
- dsRNA
- ssRNA
15
Q
In what SHAPE is viral genetic info. encoded?
A
linear, circular, or segmented
16
Q
How many nucleotides (base pairs) will you find in a virus?
A
from thousands to 250,000
17
Q
What is the CAPSID?
A
protein coat that protects the nucleic acids of viruses
*accounts for most of the mass of a virus
18
Q
What is a CAPSOMERE?
A
protein subunits that assemble to form the capsid
19
Q
What are some viral capsids coated with?
A
an envelope of carbohydrates, proteins, and lipids.
*Although the proteins of the envelope are encoded by viral genes
*some of the envelope’s components derive from host-cell constituents
20
Q
Disadvantages of a viral envelope?
A
sensitive to drying out
21
Q
Viral SPIKES
What are they used for (by scientists)?
Purpose of them?
A
- to identify certain viruses
- facilitate host-cell attachment
*facilitates specific host-cell interaction through hydrogen bonds and ionic bonds
22
Q
How could we exploit viruses to treat human disease?
A
?
23
Q
Phage Therapy
A
the therapeutic use of bacteriophages to treat pathogenic bacterial infections
24
Q
Gene Therapy
A
Treating a disease by replacing abnormal genes
25
Hemaglutination
Clumping of RBC's
26
What are the two important proteins in the envelope?
hemaglutinin and neuraminidase
\*hemaglutin binds to sialic acid on surface of cells
– 16 DIFFERENT HA
\*neuraminidase necessary for budding
– 9 DIFFERENT NA
27
What s H5N1?
the bird flu everyone is so worried about
1. human subtypes
- H1N1, H1N2, H3N2
2. H5, H7 occur mainly in birds
3. Pigs are susceptible to both avian and human flu subtypes.
4. Flu genome is segmented = allows mixing in intermediate host, like the pig.
28
Antigenic Shift
When two different viruses meet in a host, a new, unique virus can be created.
29
Antigenic Drift
when mutations in the genome permit the proteins to evade recognition by the host’s immune system.
This is usually why new strains of the flu exist each year.
\*host produces antibodies, but the pathogen mutates
many pathogen, not just viruses, exploit antigenic drift
30
Taxonomy of Viruses
3 Orders -*ales*
73 Families -*viridae*
9 Subfamilies -*virinae*
287 *Genera* -virus
Common name
## Footnote
31
Viral Species
a group of viruses sharing the same genetic information and ecological niche (host range)
32
Viruses must be cultured in ______ cells.
Live
* bacteria
* living animals
* chicken egg
* cultured cells
33
Bacteriophage
A virus that infects bacteria
34
Explain viral concentration and bacteria counting
Viral concentration is measured in plaque forming units, or PFUs
* Bacteria are mixed with a dilution of virus in a pour plate method.
* The bacteria are destroyed by the virus, creating a plaque.
35
What are viral genes most concerned with in the encoding process of viral structural components?
Replication or processing of viral nucleic acid
\*the host cell provides everthing else
36
What is the ECLIPSE PERIOD?
the time after infection during which no new virions are detected
37
Why does the eclipse period exist?
Most new cells die after infection, therefore no new virions are produced after infection.
38
Name two ways that Bacteriophages can multiply
Describe them...
Lytic Cycle
Lysogenic Cycle
39
Why have scientists extensively studied bacteriophages?
bacteria are easily grown in the lab…they culture easily
40
Name the stages of the LYTIC CYCLE
1. attachment (adsorption)
2. penetration
3. biosynthesis
4. maturation
5. release
41
How do you think the virus is able to overwhelm the host cell’s transcription and translation machinery?
1. degrade host cell DNA
block transcription
block translation
2. Overpowers by simply fitting next to each other…heavy attraction btween viral mRNA and
42
Which enzymes is necessary for T4 phage entry into and exit from a host bacterial?
Lysozyme
43
What does a virus do in the lysogenic cycle?
1. infect a cell
2. incorporate their genetic material into that of the host cell, and then…
3. wait (become latent)
44
Which "trigger" can induce the lytic cycle from a lysogenic state?
UV Light
45
What are the 3 results from LYSOGENY?
1. immunity from reinfection (by same phage)
2. phage conversion
3. specialized transduction
46
Why would UV light trigger a latent virus to become lytic?
UV light damages DNA, leading to cells uncontrollable diving. Viruses needs to exit and does
47
Name the stages of Viral Multiplication in ANIMALS
1. attachment
2. entry
3. uncoating
4. biosynthesis
5. maturation
6. release
48
What are the (2) types of viral ENTRY into Animal Cells?
1. receptor-mediated endocytosis
2. pinocytosis / fusion (enveloped viruses)
49
Neutralizing Antibodies are the ___________ of many vaccines
Strategy
50
In Animals, Viral DNA moves to the _________ after attachment and entry.
What (2) steps follow?
Nucleus
1. The DNA is transcribed and translated.
2. Then, the DNA is replicated and the virus assembles.
51
Viral RNA remains in the cytoplasm
1. Some RNA viruses produce an RNA-dependent RNA polymerase that copies the RNA strand into its complement.
2. + (sense) / - (antisense)strands
52
RNA-dependent RNA polymerase does not have high fidelity, meaning that it makes many mutations. Which of the following is common in RNA viruses that utilize RNA-dependent RNA polymerase?
* antigenic shift
or
* antigenic drift
?
\*Mutation accumulating that leads to a slightly different product --\> virus might be able to evade and be protected
53
Retrovirus
produces a reverse transcriptase enzyme that copies RNA into DNA
THE VIRAL RNA REMAINS IN THE CELL
\*The DNA is inserted into the host cell’s genome
\*This is how HIV can remain latent and be protected from antiviral therapy
54
What are the (2) types of Viral release occur?
1. During **budding**, the extrusion of the virus causes some of the host cell’s _membrane_ to be _incorporated into the virion envelope_.
2. During **rupture**, the _host cell is lysed_.
55
Acquired Immunodeficiency Syndrome
(AIDS)
1. HIV = human immunodeficiency virus
2. HIV-1, HIV-2 (#2 is not often found in West Africa)
3. AIDS is final stage of long infection.
4. enveloped retrovirus with gp120 (protein) surface spikes
5. different clades (subtypes)
M (main), O (outlier), N (non-M or non-O)
56
Which type of nucleic acid is contained in an HIV virion?
RNA (b/c its a retrovirus)
57
HIV evades host immune defenses by undergoing rapid antigenic changes.
True or False?
TRUE
| (reverse transcriptase also makes mutations)
58
AIDS
| (Characteristics/stats)
* HIV = human immunodeficiency virus
* 33 million infected
* intimate sexual contact
* blood transfusion
* contaminated needles
* breast milk, placental transfer
* healthcare workers at greater risk
* 67% in sub-Saharan Africa = 5.2% of population
59
How is HIV spread IN the body?
* spread by dendritic cells to activated T cells in lymph nodes
* gp120 attaches to CD4+ receptor on CD4+ T helper cells; CCR5 and CXCR4 are coreceptors
60
Is HIV lytic, lysogenic or both?
Both
\*evades immune system
long-lived T memory cells can contain provirus (latent virus)
61
AIDS
(Stage 1)
Stage 1: many viruses made, lymphadenophathy (swollen lymph nodes)
62
AIDS
(Stage 2)
Stage 2: declining CD4+ T cell count, opportunistic yeast infections
63
AIDS
(Stage 3)
*C. albicans* infections
cytomegalovirus eye infections
*tuberculosis*
*PCP* (fungal pnemonia)
*toxoplasmosis* of the brain
*Karposi*’s sarcoma
64
What happens to CD4+ T cells as AIDS progresses
* Number declines as the cells’ lifespans are shortened, and the body fights to keep up production.
* Although CTLs are effective (Igs are not), HIV establishes a pool of latently infected CD4+ T cells.
65
AIDS stats
* Elderly and infants/children cannot produce enough CD4+ T cells.
* 20% of infants born to HIV-positive mothers are infected.
* 1-3% of population lacks CCR5 and are resistant to infection.
66
Describe the general characteristics of viruses
* Virus means “poison”.
* Viruses are obligate intracellular parasites.
* Animals, plants, protists, fungi, and bacteria are susceptible to viral infection.
* Usually viruses infect one species
* sometimes a virus can infect more than one host species
* contain a single type of nucleic acid, either DNA or RNA
* contain a protein coat
* multiply inside living cells using the cellular machinery
* cause synthesis of specialized structures that transfer viral genetic information
