The restriction enzymes are called ‘molecular scissors’. Restriction enzymes are DNA-cutting enzymes present in bacteria. They are obtained from them for use in genetic engineering-rDN A technology. As sequence are cut within the DNA molecule, they are often called restriction endonucleases.
A restriction enzyme recognizes and cuts DNA only at a particular sequence of nucleotides. For example, the bacterium Hemophilus aegypticus produces an enzyme named Hae III that cuts DNA whenever it identifies the recognition sequence.
A cut is made between the adjacent G and C. Hae III cleaves both the strands of DNA at the . same base pairs producing “blunt” ends.
Examples : EcoRI, Hind III and Bam HI.
