viruses Flashcards
examples of viruses
bacteriophages
retroviruses
retrovirus
RNA viruses that use reverse transcriptase to create double stranded DNA transcripts from single stranded RNA genome
bacteriophage
viruses that infect bacterial cells
bacteriophage structures
sheath - helps eject viral DNA into host
tail fibers - help with recognition and attachment
viral nucleic acid (viral genome)
double or single stranded RNA or DNA
prophage
viral genome integrated into bacterial genome
provirus
viral genome integrated into eukaryotic genome
capsid
protein coat enclosing and protecting nucleic acid
viral envelope
outer membrane layer
composed of host cell membranes, other membrane proteins, and viral glycoproteins
- formed from infected host’s cell plasma membrane during the release of viral life cycle
- enveloped viruses are typically found in animals
do viruses and bacteria both have nucleic acids
YES
shared commonality with living organisms
viral infections in humans
disruption of host genes involved in cell replication by injection/integration of viral genome can lead to cancer cell development
acute infection
rapid onset of symptoms and virion replication - brief and resolve in days
chronic infection
initial period of high viral load > reduced to low once immune system controls infection > lasts several years to a lifetime
latent infection
intermittent phases of high and low viral loads after initial acute»_space; lasts years to a lifetime
slow progressing infection
seems dormant after initial viral load but progresses (viral replication) years later
bacterial defense against viruses
- cell surface mutations prevent phages from identifying bacterial surface proteins
- if phage DNA is inside the cell restriction enzymes cut at specific recognized sequences to prevent replication
- CRISPR-Cas system
CRISPR Cas
internal defense of bacteria that recognizes and cuts out viral genomes
used in biotechnology for genome editing
viral outbreaks (2 types)
epidemic - large population
pandemic - global impact
vaccines
weakened agents that mimic disease-causing organism to stimulate immune system
viral modifications can be… (2)
antigenic shift
antigenic drift
antigenic shift
viruses mix genes to increase host ranges
difficult to treat
antigenic drift
minor changes in viruses allow for infection of same host species
prions
infectious misfolded proteins that cause other proteins to misfold into the prion form
viroids
single stranded RNA molecules that infect plants
viral life cycle + methods of replication for bacteriphage
- attachment
- entry
- uncoating
- synthesis/replication
- self-assembly
- release
- attachment
between host cell and specific viral surface proteins
- virus has host ranges (set of species it can infect)
- can be limited in type of tissue
- entry
depends on type and host cell
bacteriophage inject genome into bacterial host cell using protein tail
enveloped viruses will fuse their viral envelopes with host membrane and other viruses are taken in via endocytosis
- uncoating
once inside host viral genome is exposed via breakdown of viral capsid
- synthesis/replication
virus replicates its genome and viral proteins
requires host’s nucleotides, enzymes, and ribosomes
- self-assembly
viral components spontaneously assemble into new complete viral particles called virions
- release
where viral shedding allows newly replicated viral particles to leave host
via budding, apoptosis, exocytosis
lytic cycle
bacteriophage infects and injects genome into host cell then transcribes it into viral particles that are assembled into new viruses - host cell bursts and is destroyed while virus replicates and attacks other cells
active process where phage replicates in host cell
lysogenic cycle
passive process - bacteriophage integrates into host genome without actively creating new viral particles
every time host cell replicates viral genome replicated as well
- viral genome may later be triggered to enter lytic cycle to produce new viral particles
