Lec 1: Introduction Flashcards
virus =
a very small, non-cellular parasite of cells
virus genome is composed of either,
&…
DNA or RNA,
& enclosed in a protein coat
submicroscopic =
too small to see under scope
viruses are obligate
intracellular parasites
largest virus aka
is bigger than
“Mimivirus”
is bigger than smallest bacteria
are viruses always smaller in size than bacteria?
what about their genome size?
Mimivirus has larger anatomical size AND genome size than smallest bacteria (mycoplasma)
why do we study viruses? (3)
- some viruses cause disease
- some viruses are useful
- virus studies have been contributed to knowledge
Uses for viruses (6) & examples (4):
- ) phage typing of bacteria (ex: salmonella species)
- ) sources of enzymes (ex: reverse transcriptase)
- ) pesticides (ex: baculoviruses controls some insects)
- ) anti-bacterial agents
- ) anti-cancer agents (ex: genetically mod.’d viruses infect & destroy cancer cells, but do not harm normal cells)
- ) gene vectors
Much of the basic knowledge of ___ _______, ________ ______, & ____ has been derived from studies of _______
2 examples of major discoveries =
cell biology, molecular biology, & cancer
viruses
ex: Alfred Hershey & Martha Chase Experiment, Introns
Hershey-Chase Experiment proved
that DNA is the genetic material that comprises genes
Hershey-Chase Experiment explanation:
Using bacteriophages,
- ) sulfur labeled protein capsule, infection, centrifugation…. no sulfur in cells
- ) phosphorous labeled DNA, infection, centrifugation… phosphorous in cells!
Studies of Adenovirus transcription allowed for the discovery of
introns
introns =
section of DNA that doesn’t transcribe/code for genes
RNA splicing =
joining of exons in a precursor molecule
virus particles are produced from the assembly of…
while others…
preformed components…
…while others grow/reproduce from division
virions =
virus particles
virions do not
grow or divide
viruses lack
the genetic information that encodes tools necessary for the generation of metabolic energy or protein synthesis (ribosomes)
a virus genome is composed of one of the following: (4)
ssDNA
dsDNA
ssRNA
dsRNA
viruses have
genes
viruses use
&…
host cells proteins
…genomes of large viruses duplicate some of the functions of the host cells, but the small viruses rely heavily on functions of the host cell
viruses code
&…
efficiently
…there may be overlapping genes encoded within genes
many virus proteins are
&…
multifunctional
…a virus protein may have several enzyme activities
Humans = _ genes = _ proteins Viruses = _ genes = _ proteins
Humans = 1 genes = 1 proteins Viruses = 1 genes = multiple proteins
does the human genome have some viral genes?
yes
3 reasons why viruses aren’t alive:
- ) Viruses don’t reproduce by division, but are assembled from preformed components
- ) Viruses can’t make their own energy or proteins
- ) A virus-infected cell is more like a factory than a womb
a new virion is never formed from
a pre-existing virion
Viruses need: (3)
- ) building blocks such as Amino Acids and Nucleosides
- ) protein-synthesizing machinery (Ribosomes)
- ) energy, in the form of ATP
2 reasons why viruses are alive:
- ) viruses have genes and when they infect, these genes are replicated
- ) viruses outside of host cell exist as virions, which are inert, and t.f. non-living… but bacterial spores are inert and not considered to be nonliving
