Lecture 9/10: Viruses Flashcards
what is a virus?
genetic element encapsulated in a protein shell
what is a capsid?
protein shell
why are viruses not considered living?
does not have independent metabolism
T or F: viruses do not need a host to carry out energy & protein synthesis
false, they use phages
what is a virion?
extracellular form of a virus
what is the structure of a virus?
- contains DNA or RNA
- has 1 or more fragments
what is a naked virus?
has no membrane around it
what symmetry is rod shape?
helical
what symmetry is spherical shape?
icosahedral
what is the length & width of a helical virus dependent on?
length- nucleic acid strand length
width- size & packaging of capsomeres
what is an example of a helical virus?
TMV
what is icosahedral symmetry?
20 triangular faces + 12 vertices (corners)
what symmetry is the most simple/effective?
icosahedral
where does the phospholipid bilayer in envelope viruses come from?
the host
what are fibrils?
peptidoglycan-like polymer on amoeba viruses
where is the protein found on spike viruses?
surface
what is the function of spike proteins?
attach & enter host cells
what is bacteriophage?
lysozome-like enzyme
what are RNA viruses?
RNA replicase (mRNA->mRNA)
what are retroviruses?
reverse transcriptase (RNA->DNA)
what type of genetic material are viruses missing?
mRNA
why do viruses have fast evoltuion?
due to high error rate
Species name vs Viral name: Italics/not in italics?
species- italics
viral name- not in italics
what is the Baltimore classification?
classifies viruses by nucleic acid type & replication
how many groups does the Baltimore classification have?
7 groups
central dogma of viruses
RNA -> Protein
RNA -> DNA
what can DNA/RNA strand be used for using the Baltimore classification?
template for translation
what is the negative strand used for?
complementary mRNA sequence
can the negative strand in RNA be used as a template for translation?
no because it must create a copy
Lytic infections
new phages are produced
Lysogeneic infection
viral DNA is replicated
Persistent
chronic & still infectious
Latent infections
dorminant & non-infectious
what is the 1st step for infection of eukaryotics
attach
what are the 7 steps of the baltimore classification?
- ds DNA
- ss DNA
- ds RNA
- (+) RNA
- (-) RNA
- reverse RNA
- reverse ds DNA