These are the types in the cutting of DNA fragments into pieces.

2. RESTRICTION ENZYMES
• Produces by bacterial cells to protect themselves
against the foreign in bided DNA
• There are three major activities of RE’s:
1. Recognition
2. Digestion (or)
3. Modify
(Methylase)
There are two types of methylase:
1. dAM (A residue)
2. dCM (C residue)

3. TYPES OF RE
• Depending upon the source of isolation
& the biochemical activity,
RE’s are of THREE groups.
[The first enzyme discovered which recognizes
a given sequence is
known as the prototype.] 1. Isoschizomer
2. Neoschizomer
3. Isocaudomer

4. Isoschizomer
• Pairs of restriction enzymes isolated from two different
sources having exactly the same recognition site and
also exactly the same digestion/cleavage site.
• SphI (CGTAC/G) and BbuI (CGTAC/G) are isoschizomers
S1 S2

5. Neoschizomer
• Pairs of restriction enzymes isolated from two
different sources having exactly the same recognition
site but the site of digestion/cleavage of S1 and S2
varies.
• Smal(CCC/GGG) and XmaI (C/CCGGG) are
neoschizomers.
S1 S2

6. Isocaudomer
• Pairs of restriction enzymes isolated from two
different sources having different recognition site but
the digestion site for S1 & S2 is exactly the same.
• Produces compatible ends (having similar type of
ends)
• Mbo I and BamH I are isocaudomers.
S1 S2