Download Restriction Enzymes

Restriction Enzymes
Restriction Endonucleases
Also called restriction enzymes
“molecular scissors” discovered in in bacteria
Restriction enzymes is an enzyme that cuts doublestranded or single stranded DNA at specific nucleotide
sequenced known as restriction sites.
3000 restriction enzymes have been identified
Restriction Endonucleases
Named for bacterial genus, species, strain, and type
Example: EcoR1
Genus: Escherichia
Species: coli
Strain: R
Order discovered: 1
Restriction Endonucleases
Recognition sites have symmetry (palindromic)
“Able was I, ere, I saw Elba”
5’-GGATCC-3’
Bam H1 site:
3’-CCTAGG-5’
Restriction Endonucleases
Enzymes recognize specific 4-8 bp sequences
Some enzymes cut in a staggered fashion - “sticky
ends”
EcoRI
5’…GAATTC…3’
3’…CTTAAG…5’
Some enzymes cut in a direct fashion – “blunt ends”
PvuII
5’…CAGCTG…3’
3’…GTCGAC…5’
Restriction Endonucleases
Why don’t bacteria destroy their own
DNA with their restriction enzymes?
Methylation
Ways to use Restriction
Enzymes
Cut DNA into fragments so that it would be
easier to study, identify and characterize
genes.
 Use a device for recombining, or joining ,
DNA molecules from different genomes.
Usually used to identify and characterize a
gene or studying gene expression and
regulation.
