1. Restriction Enzymes

2. Restriction Endonucleases Also called restriction enzymes “molecular scissors” discovered in in bacteria Restriction enzymes is an enzyme that cuts double- stranded or single stranded DNA at specific nucleotide sequenced known as restriction sites. 3000 restriction enzymes have been identified

3. Restriction Endonucleases Named for bacterial genus, species, strain, and type Example: EcoR1 Genus: Escherichia Species: coli Strain: R Order discovered: 1

4. Restriction Endonucleases Recognition sites have symmetry (palindromic) “ Able was I, ere, I saw Elba ” Bam H1 site: 5 ’ -GGATCC-3 ’ 3 ’ -CCTAGG-5 ’

5. Restriction Endonucleases Enzymes recognize specific 4-8 bp sequences Some enzymes cut in a staggered fashion - “sticky ends” EcoRI 5’…GAATTC…3’ EcoRI 5’…GAATTC…3’ 3’…CTTAAG…5’ 3’…CTTAAG…5’ Some enzymes cut in a direct fashion – “blunt ends” PvuII 5’…CAGCTG…3’ PvuII 5’…CAGCTG…3’ 3’…GTCGAC…5’ 3’…GTCGAC…5’

7. Restriction Endonucleases Why don’t bacteria destroy their own DNA with their restriction enzymes?

8. Methylation

9. Ways to use Restriction Enzymes Cut DNA into fragments so that it would be easier to study, identify and characterize genes. 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. 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.