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.