Explain restriction enzymes and their nomenclature.

(N/A) In the year $1963$,two enzymes responsible for restricting the growth of bacteriophage in $Escherichia$ $coli$ were isolated. One of these added methyl groups to $DNA$,while the other cut $DNA$.
The enzymes which cut $DNA$ are called restriction endonucleases.
$Hind-II$ was the first restriction endonuclease enzyme discovered.
$Hind-II$ always cuts $DNA$ molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for $Hind-II$.
Besides $Hind-II$,today we know more than $900$ restriction enzymes that have been isolated from over $230$ strains of bacteria.
Nomenclature: The naming of these enzymes is based on the bacteria from which they are isolated. The name consists of three or four letters.
For example,in $EcoRI$:
- The first letter '$E$' comes from the genus $Escherichia$.
- The next two letters '$co$' come from the species $coli$.
- The letter '$R$' is derived from the name of the strain $(RY13)$.
- The Roman numeral '$I$' indicates the order in which the enzymes were isolated from that strain of bacteria.