Chapter 19: Viruses Flashcards
virus
infectious particle; genes packaged in protein coat
tobacco mosaic virus
stunts tobacco growth and gives leaves a mottled coloration.
capsid
protein shell enclosing viral genome
capsomeres
protein subunits of capsids
helical virus
has a capsid made up of a single type protein arranged in a helix
icosahedral virus
capsid with 252 identical protein molecules arranged in a polyhedral capsid with 20 triangular faces
adenovirus structure
icosahedral capsid with glycoprotein spike at each vertex
influenza virus
outer envelope studded with glycoprotein spikes; genome is 8 different RNA wrapped in helical capsid
viral envelopes
membranous envelope surrounding capsid. have host cell phospholipids and membrane proteins. also has viral proteins and glycoproteins.
phage
virus that infect bacteria
T-even phages
elongated icosahedral head enclosing DNA and a protein tail (attaches to bacterium)
ex: T2, T4, T6
host range
number of host species a virus can infect
viral replicative cycle
- virus binds to host cell and inserts viral genome
- host enzymes replicate viral genome
- host enzymes transcribe viral genome into viral mRNA to make capsid proteins
- viral genomes and capsids form new virus particles which exit the cell
lytic cycle
phage replicative cycle that kills host
virulent phage
phage that only replicates by lytic cycle
restriction enzymes
cut up foreign DNA in bacteria
lysogenic cycle
allows replication of phage genome without killing the host
temperate phages
phages that use both lysogenic and lytic cycles; environmental signal induces phages to initiate lytic cycle
prophage
viral DNA integrated into bacterial DNA. can eventually form active phages that lyse host cells
adenovirus
dsDNA
- no viral envelope
- respiratory + tumor-inducing viruses
papovavirus
dsDNA
- no viral envelope
- papillomavirus (warts, cervical cancer), polyomavirus (tumors)
Herpesvirus
dsDNA
- yes viral envelope
- herpes simplex 1 and 2 (cold+genital sores), varicella zoster (shingles, chickenpox), Epstein-Barr virus (mononucleosis, Burkitt’s lymphoma)
poxvirus
dsDNA
- yes viral envelope
- smallpox, cowpox virus
parvovirus
ssDNA
- no viral envelope
- B19 parvovirus (mild rash)
reovirus
dsRNA
- no viral envelope
- rotavirus (diarrhea), Colorado tick fever virus
picornavirus
ssRNA (serves as mRNA)
- no viral envlope
- rhinovirus (cold), poliovirus, hepatitis A, other enteric viruses
coronavirus
ssRNA (serves as mRNA)
- yes viral envelope
- SARS (sever acute respiratory syndrome)
flavivirus
ssRNA (serves as mRNA)
- yes viral envelope
- yellow fever, West Nile, hepatitis C virus
togavirus
ssRNA (serves as mRNA)
- yes viral envelope
- rubella virus, equine encephalitis virus
filovirus
ssRNA (template for mRNA synthesis)
- yes viral envelope
- Ebola
orthomyxovirus
ssRNA (template for mRNA synthesis)
- yes viral envelope
- influenza virus
paramyxovirus
ssRNA (template for mRNA synthesis)
- yes viral envelope
- measles, mumps
rhabdovirus
ssRNA (template for mRNA synthesis)
- yes viral envelope
- rabies virus
retrovirus
ssRNA (template for DNA synthesis)
- yes viral envelope
- HIV/AIDS, RNA tumor viruses (leukemia)
herpesvirus (description)
has a temporary membrane using host cell nuclear membrane. sheds membrane in cytoplasm. gets new membrane from Golgi. copies of viral genome can remain in certain nerve cell nuclei and be latent.
reverse transcriptase
enzyme that transcribes RNA to DNA in retroviruses.
HIV
retrovirus that cases AIDS. has an envelope and 2 ssRNA and 2 reverse transcriptase molecules
provirus
integrated viral DNA in animal virus
HIV replicative cycle
- glycoproteins on viral envelope bind to white blood cell receptors
- viral membrane fuses and viral RNA and proteins released into cell
- reverse transcriptase makes dsDNA
- dsDNA inserted as provirus into cell’s DNA
- proviral genes make RNA molecules and viral proteins
- vesicles transport glycoproteins to plasma membrane
- capsids assembled around viral genomes and reverse transcriptase and bud off
transposons
DNA segments that can move around in a cell’s genome
mimivirus
dsDNA virus with 400nm diameter icosahedral capsid. 1.2 million bases and 1000 genes
vaccine
harmless variant of pathogen that stimulates immune system defense against harmful pathogen
acyclovir
drug that stops herpes replication by inhibiting viral polymerase
azidothymine
stops HIV replication by interfering with reverse transcriptase
epidemic
general outbreak of a disease
pandemic
global epidemic
Influenza A
infects many animals and cause major epidemics (“spanish flu”)
horizontal transmission
plant infected from external source of virus
vertical transmission
plant infected from a parent (such as asexual propogation or sexual reproduction)
viroids
circular RNA molecules that infect plants
- cadang-cadang: killed 10 million + coconut palms in Philippines
prions
infectious proteins
- scrapie (sheep), mad cow disease, Creutzfeldt-Jakob disease
- induces other proteins of same type to fold into abnormal shape and turn into prion
- 10+ year incubation period
