Restriction digests

Restriction digests also known as restriction enzymes/endonucleases. They are enzymes found in bacteria. They cut specific sequences of DNA: 4 to 8 base pairs approximately at sites called recognition sites. The endonucleases cleave the sugar-phosphate backbone of DNA. Restriction digests commonly used are EcoRI, BamHI and HindIII.

When the enzyme cleaves the DNA- they generally produce 3 different types of cleavage:

• With 5' or 3' ends where the unpaired bases will be produced on both ends of the fragment.
• Blunt ends where the recognition site is cut in the middle.

After restriction digest, DNA can then be analysed using agarose gel electrophoresis. This is very useful in recombinant DNA therapy .