Viruses Flashcards
(20 cards)
What is a virus (aka virion)?
A genetic element Replicate independently of host’s chromosome but not the host itself 1. can survive outside of a cell for long periods of time (composition and coating) 2. must attach and enter (infect) a host cell 3. hijack host cells’ machinery to replicate themselves 4. exit and transmission
Which domains can viruses infect?
All of them
What percent of the human genome is comprised of viral DNA?
8%
Naked virus
Nucleic acid (DNA or RNA) surrounded by protein coat (capsid); no lipid
Enveloped virus
coat + lipid bilayer (allows fusion w/ host)
Viroids
Infectious nucleic acid with no protein coat (devoid of a coat)
Ex. potato spindle viroid (around 1960s)
Prions
Infective proteins
eg. mad ocw or Creutzfeldt-Jakob
incorrectly or abherrantly folded proteins
What is the genome of a viroid like?
Tiny and small, but has the highest per site mutation rate of all biological entities
Hemi-fusion
Envelope Fusion
Endocytosis
T4 bacteriophage
Useful in transduction
Measles and RSV enter through which method?
Budding
Synthetic Virus Drug Delivery system
Bacteriophage: Lytic Cycle
causes lysis: virulent phage
Phage quickly replicates, kills host cell
generally lytic when host cell conditions are good
bacteria divide quickly but phage replicates even faster
or conditions are unfavorable (eg cell damaged)
top in picture
Lysogenic cycle (bacteriophage)
(genic –> genome) temperate
Phage is quiescent
may integrate into host cell genome
replicates during host cell division
generally lysogenic in moderate cell conditions
phage can reactivate to become lytic kill host
What are viruses classified by?
by genome structure and polymerase type
Baltimore virus classification
emphasizes the form of the genome (DNA or RNA, single or double) and the route to generate messenger RNA
Retroviruses
use a reverse transcriptase to copy their genomic sequence into DNA for insertion in the host chromosome
Virus to bacteria ration
1: 100 in marine and aquatic environment
1: 1000 in soils
