An Intro to Viruses Flashcards
acellular
not consisting of cells
obligate intracellular parasites
inert and incapable of reproduction outside of cells
bacteriophage
complex viruses capable of infecting bacteria
host range
spectrum of host cells (both the kind of organism and the type of cell) that a particular pathogen can infect
restriction enzymes
proteins that recognize specific DNA sequences and cleave them at or near the recognition site
CRISPR
a gene modification system
virome
collective viral community present in a specific environment or within a particular host organism
oncogenic
have some involvement in the development of transformed/cancerous cells
virion
mature virus particle
nucleocapsid
nucleic acids surrounded by a protein coat
nucleic acids
DNA or RNA
capsid
protein coat that protects viral nucliec acids
protomer
protein subunits that make up the capsid
capsomere
made of protomers and determines shape of the virus
helical capsid
protomers form a rigid hollow tube
icosahedral capsid
regular polyhedron with 20 equilateral triangular faces and 12 vertices
Capsid of Complex Symmetry
not helical or icosahedral
Capsid of Complex Symmetry
poxviruses
largest animal viruses with ovoid to brick shap exteriors
Capsid of Complex Symmetry
complex phage
binal symmetry with icosahedral head and helical tail
Naked capsid virus
- Advantage?
virion includes only a nucleocapsid
- remain infectious outside of the body for longer compared to eveloped viruses
enveloped virus
- disadvantage?
virion includes nucleocapsid and envelope
- need fluid for transmission
virus envelope
lipids and carbohydrats acquired from host membrane and envelope proteins called spikes which are encoded by the virus
spikes
- function?
envelope proteins
- host cell attachment
- antigenic
- enzyme function
Virion Enzymes for Infection//Biosynthesis
lysozyme
- encoded by phage
- makes hole to allow for entry of phage nucleic acids
- produced at the end of biosynthesis to lyse the host bacterial cell
Virion Enzymes for Infection//Biosynthesis
neuroaminidase
- spike protein encoded by influenze that has enzymatic activity
- supports separation of the envelope from the host cell during release
Virion Enzymes for Infection//Biosynthesis
Nucleic acid polymerase
support replication of viral nucleic acids that host cell cannot replicate
Virion Enzymes for Infection//Biosynthesis
RNA replicase
RNA-dependent RNA polymerase encoded by RNA viruses
Virion Enzymes for Infection//Biosynthesis
reverse transcriptase
converts retrovirus RNA into DNA
Virus Classification
The Baltimore Scheme
- developed by David Baltimore
- groups viruses based on relationship between their genomes and mRNA
- DOES NOT describe relationship between viruses
Virus Classification
International Committee on Taxonomy of Viruses (ICTV)
- uses host range, structural morphology, replication cycle, nucleic acid sequence and pathogenicity to classify
Steps in the Viral Replication Cycle
Eclipse Phase
time when no virions are detected in or outside of cells (genome is being replicated and protein synthesized)
Steps in the Viral Replication Cycle
Maturation
packaging of nucleic acids in capsids (first virion detected)
Steps in the Viral Replication Cycle
burst size
number of virions released, increases during maturation and then plateaus
Steps in the Viral Replication Cycle
Latent period
eclipse + maturation phases
Steps in the Viral Replication Cycle
attachment
ligand on the virion attaches to a receptor on the host cell
Steps in the Viral Replication Cycle
entry
genome alone or entire nucleocapsid or virion enters the host cell
Steps in the Viral Replication Cycle
synthesis
viral nucleic acids are synthesized/replicated and viral proteins are syntehsized
Steps in the Viral Replication Cycle
assembly
nucleic acids are packaged in the capsid
Steps in the Viral Replication Cycle
release
host cell lysis or budding occurs
