Question

Explain in detail the role of restriction endonuclease in formation of recombinant DNA. Draw a labelled diagram of E.Coli cloning vector pBR 322.

Answer 1

A restriction enzyme (restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Restriction enzymes are of great use in genetic engineering for restricting desired genes for incorporation. The restriction enzymes are used for the cleavage of the desired gene from the isolated DNA and the plasmid vector. There are specific recognition sites which are used for the cleavage. Certain enzymes produce sticky ends which can be ligated while the introduction of the gene in the vector.

There are various vectors which are used in genetic engineering for the introduction of the desired genes in the host cells. pBR322 is one of the common plasmid vectors. The size of this vector is 4361 bp. There is an ori site which is the site for replication. There are multiple recognition and cloning sites which are used for the insertion of genes. There are antibiotic resistance genes like ampicillin ($am{p}^R$) and tetracycline ($te{t}^R$).