Their discovery by Hamilton Smith, Werner Arber, a
Their discovery by Hamilton Smith, Werner Arber, and Daniel Nathans led to the Nobel Prize in Physiology or Medicine.  Often found in various bacteria or yeast cells, they are divided into three classes with the first and third classes being similar in that all methylase activities are conducted by one complex.  Common examples include Bam-H-1 and Eco-R-1, the first to be discovered.  The key component of gene splicing, they target specific short sequences in a DNA strand that are usually palindromic.  Designed to chop up foreign DNA that may be detrimental, they cleave around those palindromic sequences.  FTP, name this class of enzymes.
Their discovery by Hamilton Smith, Werner Arber, and Daniel Nathans led to the Nobel Prize in Physiology or Medicine.  
{Restriction Enzymes} or {Restriction Endonucleases}