Lecture 4 (Virus and Acellular infectious agents) Flashcards
1
Q
What makes up a virus?
A
proteins and nucleic acids
2
Q
What codes for a viroid?
A
only RNA
3
Q
What is a satellite cell made of?
A
nucleic acids
4
Q
What are prions?
A
small infectious molecule composed of abnormally folded proteins
5
Q
Describe the general properties of a virus.
A
- at least one if not more molecules of DNA or RNA surrounded by a protein coat (caspsid)
- unable to reproduce or have cell division outside living cells
- survives extracellularly
6
Q
What is a virus’ envelope composed of?
A
-proteins, lipids, carbohydrates
7
Q
What are spikes used for on the outside of a virus?
A
-aid attachment to cells, and play a major role in viral budding
8
Q
What is an obligatory intracellular parasite?
A
- parasite that infiltrates a host cell, and uses the host cells metabolic enzymes ribosomes and other proteins to replicate and divide.
9
Q
What is obligatory commensalism?
A
- one unit benefits the other and the other is essentially unharmed or does not receive any type of benefit
10
Q
What is obligatory mutualism?
A
- the infestation benefits both the host and the parasite
11
Q
What is a capsid?
A
-macromolecular structure that serves as a virus protein coat
12
Q
What does the capsid do for the virus?
A
- protects the viral genetic material and helps transfer it amongst host cells
13
Q
What is a helical capsid?
A
- capsid is a hollow tube with protein walls, that self assembles
- rabies and ebola
14
Q
What is a icosahedron type of virus?
A
- polyhedron with 20 equilateral faces and 12 vertices
- adenovirus and poliovirus
15
Q
What does a binal symmetry virus look like?
A
-rocket ship with multiple tail fibers as landing gear
16
Q
What is a good example of virus that are enveloped?
A
influenza and herpes simplex
17
Q
What is the process of multiplication of animal viruses?
A
- attachment
- penetration/entry
- uncoating
- biosynthesis
- maturation
- release
18
Q
In what ways can a virus enter into a host cell?
A
- fusion: viral envelope fuses with the host membrane
- endocytosis: enters vesicle and the endosome aids with viral uncoating
- inject nucleic acids into cytoplasm
19
Q
Which type of proteins are important for virus assembly, early or late?
A
-late proteins
20
Q
Where will assembly generally occur?
A
-can occur either in the nucleus or in the cytoplasm. This depends on the virus genome
21
Q
How are the viruses, or virions released (non-enveloped)?
A
-the host cells must be lysed with lysosymes that degrade the peptidoglycan layer, and another protein that will punch holes in the membrane
22
Q
What process do enveloped virus use in order to exit the host cell?
A
- budding
1. viral matrix proteins line the PM
2. nucleocapsid is directed to the PM
3. the PM protrudes outwards and pinches off to eject a mature virion
4. requires hemagglutinin for attachment to the PM and neuraminidase to induce the budding process
23
Q
Describe the process of DNA Virus multiplication?
A
- virion attaches to host
- virions enters host and uncoats to release DNA
- DNA moves to nucleus to start transcription
- formation of viral mRNA
- mRNA is replicated and translated to produce viral proteins
- viral proteins mature, and migrate into host nucleus
- viral proteins form capsid and the virion is released from the host cell
24
Q
What is the process for (+)sense strand RNA multiplication?
A
- attachment
- Entry and uncoating of DNA
- (+) strand must undergo transcription in order to produce a template (- strand) so that can be transcribed into mRNA
- mRNA is translated into viral proteins
- proteins mature, reform the (+) capsid and virion is released
- all processes occur in the cytoplasm and have no need to enter into the nucleus
25
What is the process for (-) antisense strand RNA multiplication?
1. attachment
2. entry and uncoating
3. the antisense strand must first produce a sense strand, and then it can undergo translation
4. translate the mRNA to produce viral proteins
5. mature proteins form the viral capsid and release from the host cell
26
Describe the processes of a retrovirus.
1. retrovirus enters via fusion, using spikes to aid attachment
2. uncoating releases reverse transcriptase, integrase, and protease
3. reverse transcriptase produces DNA from viral RNA
4. viral DNA is integrated as a provirus into host DNA, in order to replicate when the host replicates
5. provirus can be transcribed as well
6. viral proteins are processed by the viral protease, and moved to PM
7. mature retrovirus leaves the host, and acquires envelope and attachment spikes as it buds out
27
Which strand can be directly transcribed to produce mRNA?
the (-) antisense strand will
28
What is the purpose of the sense (+) strand?
-this sequence is similar to the mRNA sequence, therefore the antisense strand must be transcribed first before mRNA can be produced
29
What type of infection is characteristic of a virulent phage?
- multiplies immediately on entry
| - lyses the bacterial host cell
30
What type of reproductive opportunities do the temperate phages have?
- lytic phase (as virulent)
| - lysogenic phase
31
What is the difference between lysogenic and lytic pathways of replication?
- lytic directly produces new phages, but lyses the host cells as it leaves. Reducing number of infectable hosts
- Lysogenic phage is integrated into the host DNA, and lies dormant until a stressor triggers the provirus to be excised from the host DNA
32
What are the steps in the lytic cycle?
1. phage injects DNA into the cytoplasm
2. phage directs DNA synthesis of new phages
3. cell lyses and releases new phages to infect other bacterial cells
33
What are the steps in the lysogenic cycle?
1. phage injects into the cytoplasm
2. phage DNA integrates into the host chromosome (DNA)
3. prophage DNA is copied when the host completes cell cycle
4. stressors (UV light) trigger excision of provirus from the host chromosome
5. can generate phages and lyse the host cell
34
What are two advantages a phage utilizing lysogenic cycle can have?
1. phage remains viable but can't replicate until stressors are present. prolong the life of the phage
2. multiplicity of infection ensures survival of the host cell
35
What is induction?
the cell causes prophage to initiate synthesis of new phage particles, in response to specific environmental conditions
36
Are archaeal viruses generally lytic or temperate?
-temperate, unknown mechanism
37
What type of infection will result in cell death via lysis?
-cytocidal infection
38
What are cytopathic effects, such as degenerative changes or abnormalities?
-physical changes in the cell shape, that indicate the presence of a virus
39
Define a tumor
growth or lump of tissue; benign if located in one spot
40
Define a neoplasia.
abnormal new cell growth and reproduction due to loss of regulation
41
Define anaplasia.
reversion to a more primitive or less differentiated state of a cell
42
Carcinogenesis is a complex multistage process that generally involves an oncogene. What is an oncogene?
- cancer causing gene
- comes from a virus
- can come from a proto-oncogene that has undergone some type of mutation
43
What is a proto-oncogene?
- this is a normal cell/gene.
| - slight alteration/mutation can cause it to become an oncogene and therefore contribute to cancer formation.
44
How can viruses cause cancer?
1. viral proteins bind to the host cell's tumor suppressor proteins
2. carry an oncogene and insert it into the host genome
3. alterations in the cell cycle regulation
4. insert promoter or enhancer to a cellular oncogene
45
What is infection dose 50 (ID50)?
- this is the amount of pathogen required to infect 50% of test subjects
46
What is lethal dose 50 (LD50)?
This is the amount of pathogen required to kill 50% of the test subjects
47
What type of genetic material do viroids contain?
- closed circular ssRNA. infectious
48
What are satellites?
- infectious nucleic acids. DNA or RNA
- encode one or more gene products.
- RNAs/DNAs do not encode their capsid proteins
49
Do satellite viruses encode their own capsid proteins?
yes, but only when assisted by a helper virus
50
Why do we not need to get an immunization for Hep D?
Hep D is a satellite that requires the help of Hep B in order to replicate
51
What is a prion?
- a proteinaceous infectious particle that causes a variety of degenerative diseases in humans and animals
- alters normal protein shapes, that will spread to other cells
52
What type of role are prion proteins suspected of playing with regard to neural loss?
- the interaction of the prion protein with abnormal prion protein may form a crosslink that triggers apoptosis, where the abnormal prion protein is the infectious material
53
What are the side effects of prion caused diseases?
- no effective Tx
| - progressive degeneration of the brain that leads to death.
