Biotechnology—Principles and Processes — BIOLOGY STD 12 Science — Question

(i) Restriction enzymes are also called "molecular scissors" as they cleave DNA at or near specific recognition sequences known as restriction sites. These enzymes make on incision on each of the two strands of DNA and are also called restriction endonucleases.
Example : E coli RI cuts DNA at following sequence :
5' G A A T T C-3'
3' С Т Т А A G-5'
(ii) Molecular cloning : A popular application of restriction enzymes has been in the generation of recombinant DNA molecules. The process involves the cutting of the donor DNA (usually a plasmid) and the vector DNA (usually a gene from another organism) by a restriction enzyme to yield compatible ends. These ends could be either 'blunt' or 'sticky'. The two cleaved DNAs are joined together using an enzyme called DNA ligase to generate a recombinant DNA molecule. This recombinant DNA can, then, be introduced into a host organism for replication.