C-5 Flashcards
capsid
protein coat around virus
nucleocapsid
capsid and nuclei acid
genome
made of RNA and DNA
envelope
a phospholipid membrane that surrounds the capsid and acquired from host cell
steps of lytic vs lysogenic bacteriophage replication cycles
lytic- fills cells with viruses until it explodes so virus gets out
lysogenic- inserts own DNA into host’s DNA and stays with the cell even as it divides instead of injecting and leaving
what is lysogenic conversion and why is it important in the evolution of human pathogens
when the integrated virus gives the host new abilities and characteristics; it stays with the cell as it divides creating these new changes
steps of animal virus replication cycles
- attach to host cell
- enter host cell
- replicate genetic material and make protein
- assemble new genetic material and proteins together
- leave the cell and find a new one
how are viral genomes replicated
- replicate the genome you came into the cell with
- make mRNA that the host cell’s ribosomes can recognize and translate into protein
how are mRNAs produced to make protein capsids from host ribosomes
gene expression
how replication occurs for (+)ssRNA
reverse transcriptase
how replication occurs for (-) ssRNA
RNA-dependent RNA transcriptase
how replication occurs for ssDNA
RNA polymerase in nucleus
how replication occurs for dsRNA
positive strand of genome acts as mRNA
how replication occurs for dsDNA
cellular RNA polymerase in nucleus or viral RNA polymerase in cytoplasm
how replication occurs for retroviruses
reverse transcriptase; back in molecular time
What is meant by “positive sense” and “negative sense” single-stranded RNA?
negative sense: starts 3’-5’
positive sense: starts 5’-3’
how do enveloped viruses enter and exist cells
membrane fusion (membrane encloses around virus); endocytosis
budding (steals host cell’s plasma membrane for its own envelope; takes membrane with); lysis
how do naked viruses enter and exist cells
direct penetration (capsid empties its genome into host cel); endocytosis
exocytosis or lysis
how do bacteriophages enter and exit cells
inject DNA into cytoplasm of bacterial cell
the mature virions lyse the cell, are released, and go to infect a new cell
what enzymes are involved in replicating each type of virus based on its genome
which enzymes are provided by the host cell and which are produced exclusively by the virus
provided: DNA polymerase, RNA polymerase, ribosome
produced: RNA replicase, reverse transcriptase
lysogenic viral infections
stays with cell as it continues to divide
lytic viral infections
sometimes the host cell is killed in the process
latent viral infections
sometimes the host cell survives but the virus remains in the cell
what are adhesions? what step of replication are they necessary for?
attach step; all viruses to bind to new receptors
Describe how we treat and prevent viral infections
- antiviral drugs
- broad-spectrum strategies
- vaccines
what are nucleoside analogs and reverse
transcriptase inhibitors
generic viral enzymes; virus specific enzymes
how do antiviral drugs like these (nucleoside analogs and reverse transcriptase inhibitors) work? Why can’t we use antibiotics to treat viral infections?
target host cell functions; viruses don’t have cell walls that can be attacked by antibiotics
how can viruses cause uncontrolled cell growth and cancer
- produce a protein that inhibits cell division regulators
- integrate into host DNA and into genes that regulate cell division
cytopathic effects on viral infection
observable morphological changes in host cells that occur because of viral infections
plaques
produced by lytic HSV from lysed VERO cells in tissue culture
syncytia
formed by RSV; when the virus fuse host cells together to form one multi-nucleated mega cell
inclusion bodies
clumps of viral capsid proteins inside the cytoplasm of the host cells
Describe the methods used to culture viruses (4)
primary; harvested directly from tissue
continuous: derived from cancer cells
embryonated: can grow higher quantities of viruses - used to produce viruses (chicken eggs)
animal models: infect animals with virus
viruses
nucleic acid and protein
viroids
pieces of ssRNA that lack capsids and do not code for proteins (only RNA); replicates using host cell RNA polymerase
prions
only made of protein
