Restriction enzymes (also called restriction endonucleases) are special proteins that act like molecular scissors in genetic engineering. Their main role is to cut DNA at specific sequences, allowing scientists to easily isolate, remove, or insert genes.
Here’s how they work and why they’re important, explained:
1. Recognizing specific DNA sequences
Each restriction enzyme recognizes a particular short sequence of DNA, usually 4–8 base pairs long.
For example, the enzyme EcoRI recognizes the sequenceGAATTC
and cuts the DNA between G and A on both strands.
2. Cutting the DNA
When the enzyme finds its specific sequence, it cuts the DNA at that spot.
There are two types of cuts:
- Sticky ends: The cut leaves single-stranded overhangs that can easily join with matching sequences.
- Blunt ends: The cut is straight across both strands, leaving no overhangs.
3. Inserting new genes
In genetic engineering, scientists use restriction enzymes to:
- Cut open a plasmid (a small circular piece of DNA found in bacteria).
- Cut out a gene of interest from another DNA source.
Because both pieces are cut with the same enzyme, their sticky ends match and can be joined together using another enzyme called DNA ligase.
This creates a recombinant DNA molecule, which combines DNA from two different sources.
4. Applications
Restriction enzymes are used in many genetic engineering techniques:
- Making genetically modified organisms (GMOs)
- Producing insulin and other medicines using bacteria
- Cloning genes for research
- DNA mapping and fingerprinting
In short:
Restriction enzymes are tools that cut DNA at precise points, helping scientists remove, insert, or join genes.
They make it possible to create new genetic combinations — the foundation of modern biotechnology and genetic engineering.