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Restriction Enzymes
Contributions of Salvador Luria
Early biochemistry work was conducted on organisms with
small genomes like E. coli and viruses that prey upon them
Plate with nutrient agar would be
inoculated with bacteria and they
would be allowed to grow until
they covered the plate
Later, phages were added and they
would attack and kill the bacteria
leaving empty spots on the plate called
plaques
Salvador Luria’s Observation and
Hypothesis
• Luria observed some bacteria that were
unaffected when exposed to phages
• Luria hypothesized that these bacteria
had some type of primitive immune system
that restricted phage growth
• Luria’s hypothesis was later confirmed
by several teams of researchers when
they discovered restriction enzymes which
cut up phage DNA when it is injected into
the cell
Bacteria Evolved Restriction Enzymes
In order to reproduce,
viruses must attach to a
host cell
Phage
Viral DNA
Host Cell
Restriction Enzyme
Host Cell DNA
The virus then injects
it’s DNA into the host
cell
How Restriction Enzymes Protect Bacteria
Restriction enzymes bind
with the viral DNA at
specific base sequences
called recognition sites
The viral DNA is cut at specific
sites called restriction sites
which destroys it and protects
the bacteria from infection
Naming Restriction Enzymes
EcoR I
E
BamH I
genus
Echericia
B
genus
Co species
coli
am species
amyloliquifacience
R
Strain
R
H
Strain
H
I
Order found 1st
I
Order found 1st
Hind III
H
genus
Haemophilous
in species
influenzea
d
d
Strain
III Order found 3rd
Bacillus