Intro to virology Columbo TEST #1 1/9/17 Flashcards
What are viruses typically composed of?
- Nucleic acid (genetic material)
- Protein sheath
What is the entire viral construction outside of a cell referred to as?
-Virion
T/F
Viruses have organelles so they can replicate on their own
False
-They have no organelles, nor can they replicate on their own
Viruses are what type of parasite?
-Obligate intracellular parasites
What is the capsid?
-The outer protein sheath of a virus
What are the three shapes of capsids?
- Helical
- Icosahedral
- Complex
What type of capsid is roughly spherical?
-Icosahedral
What type of capsid is cylindrical?
-Helical
What are the three basic functions of the capsid?
- Protect the genetic material of the virus
- Aid entry into the cell in terms of attachment and or penetration of the cellular membrane
- Package viral enzymes used in viral replication
T/F
The protein sheath (capsid) helps control the specificity of a virus
True
T/F
The capsid is composed of a collection of individual repeating subunits
True
Tobacco Mosaic Virus is what type of virus?
- Helical
- Icosahedral
- Complex
Helical
What are the repeating subunits found on an icosahedral virus?
-Capsomeres
What are 5-6 individual protein structure called in an icosahedral virus?
-Protomer
If a virus pinches part of the host cells lipid membrane what are they said to be?
-Enveloped virus
Spikes or envelope proteins are made of what?
-Viral glycoproteins
If you have viral glycoproteins embedded in the enveloped virus what are they called?
-Spikes or envelope proteins
Enveloped virus typically have a layer of proteins between the capsid and envelope called what?
-Tegument or matrix protein
What helps hold the whole envelope virus together?
-Tegument or matrix protein
What type of genetic material do viruses contain?
-Either DNA or RNA
What does positive sense in terms of an RNA virus indicate?
-It can be directly translated into viral proteins (5’ to 3’) (effectively mRNA)
What does negative-sense indicate?
-Need to form a complementary strand which then can be translated into viral proteins (3’ to 5’)
What does negative sense viruses often carry within the virion?
-RNA dependent polymerase
Define ambisense?
-Contains both positive and negative sense RNA on same strand
What does sense refer to in viruses?
-The reading (translation) direction of the genetic material
T/F
Viruses use locomotion to reach cells.
False
-They depend on collision
Where do viruses attach on the naked virus?
-Capsid
T/F
Viruses can also require a co-receptor to enter a cell
True
What is the eclipse phase?
-The virus is inside the host cell and becomes off the immune system radar.
What is the process referred to that viruses use to get genetic material into the cell?
-Uncoating
What are the two pathways that enveloped viruses use to enter the cell?
- Direct fusion
- Viropexis
What type of entry does the enveloped virus such as, HIV-1, herpesviruses, or paramyxoviruses use?
-Direct fusion
What type of entry does influenza, rubella, and rabies viruses use to enter a cell?
-Viropexis
How do naked viruses typically enter a cell?
-Viropexis
In order for viruses to transcribe what must it ultimately become?
-Sense mRNA (positive RNA)
When the viral DNA folds in a way that allows replication to produce a series of repeated viral genomes is termed what?
-Concatemer
T/F
The location of viral replication determines the enzymes the virus needs to bring with them
True
What are the two phases of herpesvirus?
- Latent phase
- Lytic phase
What is the active replication phase of herpesvirus called?
-Lytic phase
What is the phase of herpesvirus when it is dormant in a circular configuration within the nucleus?
-Latent phase
RNA + (sense) viruses have genetic material that allows what?
-Directly read by host ribosomes
What do RNA + (sense) viruses need to replicate their genetic material?
-Make complementary RNA - (antisense)
What do RNA - viruses need to make?
-Complementary RNA + that can be read by host ribosomes
What does RNA - need to pack to make RNA +?
-RNA reverse polymerase
Where can RNA - viruses replicate?
- Cytoplasm
- Nucleus
What are retroviruses?
-RNA that reproduce via a DNA intermediate
What allows the formation of DNA from RNA?
-Reverse transcriptase enzyme
What integrates the viral DNA into the host genome?
-Viral integrase
When the virus is being replicated along with everything else in the cell cycle what is the stage of the virus called?
-Provirus
What is the term used to describes the insertion of individual viral genomes into individual capsids?
-Encapsidation
What is the specific site on the viral genome that codes for proteins intended to initiate assembly called?
-Packaging site
How do naked viruses typically exit the cell?
-Lysis or apoptosis
How do enveloped viruses typically exit the cell?
- Exocytosis
- Budding from plasma membrane
When you have DNA viruses what generates mRNA?
-RNA polymerase II of herpes alpha components
What are herpes alpha proteins are transcription factors for?
-Beta components
What is the concatemer cleaved into prior to assembly?
-single strand viral genomic DNA
What is a group 1 virus?
-Double stranded DNA +/-
What is a group 2 virus?
-Single stranded DNA positive sense
What is a group 3 virus?
-Double stranded RNA
What is a group 4 virus?
-Single stranded RNA positive sense
What is a group 5 virus?
-Single stranded RNA negative sense
What is a group 6 virus?
-Single stranded RNA positive sense with reverse transcriptase
What is a group 7 virus?
-Double stranded DNA turned into RNA then reverse transcribed back into DNA
In direct fusion what happens with the viral envelope?
-Stays at the plasma membrane
In direct fusion what happens to the capsid and genetic material?
-Enter the cytoplasm
What is viropexis similar to?
-Receptor mediated endocytosis
In Viropexis what happens with the virus?
-Binds the receptors on the cell surface ultimately internalizing and dragging the viral capsid along
When the virus is brought the cell via viropexis how does the genetic material get released?
-The low pH endosomal vesicle causes fusion and release of the nucleocapsid (genetic material) into the cytoplasm
