Restriction Enzymes

Introduction

• Role in Recombinant DNA Technology
  • Essential for recombining DNA.
  • Not synthesized by humans; discovered in nature.

Discovery and Function

• Initial Discovery
  • First isolated in bacteria.
• Function in Bacteria
  • Part of bacterial "immune system."
  • Protects bacteria from phage infections by cutting phage DNA.

Mechanism of Action

• Specificity
  • Recognize and cut specific DNA sequences.
  • Example: EcoR1 enzyme from Escherichia coli cuts at G-A-A-T-T-C.
  • Cuts are consistent across occurrences of the sequence in the genome.

Types of Restriction Enzymes

• Variety
  • Hundreds of types exist.
  • Named according to their origin.
• Cutting Patterns
  • Some cut sequences as short as 4 base pairs, others longer.
  • Longer sequences increase specificity.

Use in Genetic Engineering

• DNA Manipulation
  • Create "sticky ends" for attaching new DNA.
  • Allows removal and replacement of DNA segments.
  • Potential to replace defective genes with functional ones.
• Current Limitations
  • Techniques successful in single-celled organisms.
  • Challenge: applying techniques in humans.