(a) PCR :

PCR stands for Polymerase chain reaction. In this reaction multiple copies of the gene (DNA) of interest is synthesized in vitro using two sets of primers (small chemically synthesized oligonucleotides that are complementary to the region of DNA) and the enzyme DNA polymerase. The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as template. Then the process of replication of DNA is repeated many times i.e. one billion copies are made.

(b) Restriction enzyme: 

The enzymes which are responsible for ‘ restricting the growth of bacteriophage in Escherichia coli are called restriction enzymes. One of this enzyme is added to the methyl groups of DNA, while the other cut DNA. This enzyme is known as restriction endonuclease enzyme. The first restriction endonuclease is Hind II. Now more than 900 restriction enzymes have been isolated from over 230 strains of bacteria.

(c) Chitinase:

It is an enzyme obtained from fungus Trichoderma which is specialised to digest chitin of fungal cell walls. The enzyme is used both as an effective fungicide as well as dissolving fungal cell walls to obtain their protoplasts for separation of DNA is genetic engineering.