Discovered by Werner Arber, Daniel Nathans, and Hamilton Smith.
- They are known as “molecular scissors” in genetic engineering.
- They are capable of breaking DNA at specific sites called the restricted sites.
These restricted sites have Palindromic sequences.
Palindromic sequences are sequences that have the same meaning when read from both the sides just like the word ‘MADAM’ & ‘MALAYALAM’.
And sequences like:
5‘ → 3‘
3‘ → 5‘
- They break the phosphodiester bonds.
- They are found in bacteria & they protect the bacterium from foreign DNA.
- Due to methylation of its nucleotide, they don’t act on bacteria’s own DNA.
- The 1st restriction endonuclease isolated was Hind II.
- More than 900 R.E have been isolated, from 230 strains of bacteria.
- There are 3 types of R.E.Type I, II, III.
Type III is used in genetic engineering.