Explain the features of an ideal cloning vector.

A cloning vector is a DNA molecule in which foreign DNA can be inserted or integrated and which is further capable of replicating within host cell to produce multiple clones of recombinant DNA. Such a vector is called Cloning Vector. Plasmids and phages are the vectors used for cloning purposes, particularly in prokaryotes (bacteria). Characteristics of a Cloning Vector Origin of replication (ORI)

This process marks autonomous replication in vector. ORI is a specific sequence of nucleotide in DNA from where replication starts. When foreign DNA is linked to this sequence then along with vector replication, foreign (desirable) DNA also starts replicating within host cell.

Selectable Marker

Besides ORI, a cloning vector should have selectable marker gene. This gene permits the selection of host cells which bear recombinant DNA (called transformants) from those which do not bear rDNA (non-transformants).

Restriction sites

It should have restriction sites, to allow cleavage of specific sequence by specific Restriction Endonuclease. Restriction sites in E.coli cloning vector pBR322 include HindIII , EcoRI , BamHI , SalI, PvuI, PstI, ClaI  etc.

Structure of E.Coli plasmid cloning vector pBR322

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