Lecture 2 Flashcards
What 2 things does a virus need to be classified as a virus?
- Nucleic acid
- Capsid
What 2 things does a capsid do?
- Protects nucleic acid from degradation
- Has receptors that allow virus to bind and attach
What is an envelope made of?
Lipids
What are 2 things the envelopes do?
2nd layer of protection
1. protects nucleocapsid from environment
2. masks virus by looking like a self membrane
Where does the envelope come from?
It buds off from the host membrane along with host proteins
-this is why it the body recognizes it as self
What are the purpose of transmembrane proteins
- bind receptors to cell surface
- Fuses cellular and viral membranes–>lets nucleocapsid release into cytoplasm
What are the main differences between non-enveloped and enveloped viruses
Non-enveloped:
-are more stable than enveloped
-only has nucleic acid genome and protein capsid
-common in bacteria and plant viruses
Enveloped:
-less stable–>bilayer falls apart in harsh environments
-has nucleic acid, protein capsid, lipid envelope
-common in animal viruses
How do viruses contain/encapsulate their nucleic acid?
Use of repeated symmetric subunits
What are the 2 types of capsid symmetry?
- Icoshaedral
- Helical
What kind of capsid symmetry should be used if proteins are irregularly shaped and are not large enough to form 1 face?
Icosahedral
What kind of capsid symmetry should be used for negative stranded RNA viruses and need to be lengthened/shortened depending on genome
Helical
What type of capsid is the Tobacco Mosaic virus?
Helical
What are some of methods for determining viral structures
- ELectron microscopy–>whole capsids
- X ray crystallography–>individual proteins
What 3 ways are viruses classified?
- Species
- Genus
- Family
What do all viruses require to make proteins
mRNA and host ribosomes
What is Group 1 (Baltimore classification)
Double stranded DNA viruses
What is Group 2 (Baltimore classification)
Single stranded DNA viruses
What is Group 3 (Baltimore classification)
Double stranded RNA
What is Group 4 (Baltimore classification)
(+) Single stranded RNA
What is Group 5 (Baltimore classification)
(-) Single stranded RNA
What is Group 6 (Baltimore classification)
(+) Single stranded RNA w/ DNA intermdiate (Retrovirus)
What is Group 7 (Baltimore classification)
Double stranded DNA with RNA intermediate
Group 1: dsDNA characteristics
-Replicates in the nucleus
-genome is very stable
-most diverse sizes
-circular or linear genomes
What viruses are in Group 1
-Adenovirus
-Papilomavirus
-Polyomavirus
-Poxvirus
-Herpesvirus
Group 2: ssDNA
-replicates in nucleus
-small circular genomes
-non-enveloped
-genome potentially unstable
What viruses are in Group 2?
Paroviruses and Adeno-associated virus
Group 3: dsRNA characteristics
-NEEDS to bring their own RNA-dependent RNA polymerase
-segmented
-all icosahedral
-genome stable
What viruses are in Group 3?
Rotavirus
Group 4: (+) ssRNA
-can make proteins right away
-replicates in cytoplasm
-Encodes but does not need to bring in their own RNA-dependent RNA pol
-genome unstable
-most plants
What viruses are in Group 4
-SARS-COV-2
-Dengue
-Yellow fever
-Zika
-Poliovirus
-Chikungunya
-Norovirus
Group 5: (-)ssRNA
-segmented & non segmented
-NEED to bring in their own RNA-dependent RNA pol
-Genome unstable
-replicate in cytoplasm except influenza
What viruses are in Group 5
-Influenza
-Measles
-Rabies
-Ebola
-Lassa
-Nipah
-Hendra
Group 6: (+)ssRNA w/ DNA intermediate (retroviruses)
-BRING THEIR OWN RNA DEPENDENT DNA POL (REVERSE TRANSCRIPTASE)
-RNA genome is unstable but integrated DNA is stable
-DNA must integrate into host–.stays forever
What viruses are in Group 6
-HIV1
-T-lymphotrophic virus (HTLV)
Group 7 dsDNA w/ RNA intermediate
-BRING THEIR OWN RNA DEPENDENT DNA POL (REVERSE TRNASCRIPTASE)
-package in DNA form
-RNA genome is unstable, packaged DNA is stable
What viruses are in Group 7
Hepatitis B
How do we define a species
-high genome/nucleic acid similarity between diff viruses
- viruses have same host range and infect same tissues
-2 diff viruses can come into contact w/ each other/recombine
What defines a genus
-share similar genome and structure
-can have different hosts and what tissues they infect
-likely not coming in contact with/recombining
What defines a family
-evolutionary related but different
-overall same genome organization and structure
-have very different hosts and gene content
-very different genomes
How might we know if 2 viruses are in the same species?
If immune system thinks different viruses are the same
-same immune response
What is the species, genus, and family for the disease: Smallpox
Species: Variola virus
Genus: Orthopoxvirus
Family: Poxviridae
What is the species, genus, and family for the disease: Roseola
Species: Human betaherpesvirus 6A
Genus: Roseolovirus
Family: Herpesviridae
What is the species, genus, and family for the disease: COVID-19
Species: SARS-COV-2
Genus: Betacoronavirus
Family: Coronaviridae
What is the species, genus, and family for the disease: AIDS/HIV
Species: HIV-1
Genus: Lentivirus
Family: Retroviridae
What is the species, genus, and family for the disease: Rabies
Species: Rabies virus
Genus: Lyssavirus
Family: Rhabdoviridae
