pBR322 Plasmid

 

pBR322 Plasmid

The main characteristics of pBR322 are:

  • Restriction sites: BamH I, Hind III, Sal I, Pvu I, Pvu II, Pst I, EcoR I, Cla I
  • Selectable marker: antibiotic resistance genes for ampicillin (ampR) and tetracycline (tetR)
  • ORI: the origin of replication
  • ROP: It codes for proteins, which are involved in the process of replication of plasmid

Different antibiotic resistance genes act as a restriction site and to ligate foreign DNA and for the selection of transformants. The gene, where the foreign DNA is inserted becomes inactive.

Alternative selectable marker: Mostly these have an ability to produce some colour after reacting with a chromogenic substance. The alternative markers are used for the ease of differentiating recombinants from non-recombinants, e.g. gene coding for β-galactosidase.

When a foreign gene is inserted between the gene coding for β-galactosidase, the recombinant cell does not produce the enzyme β-galactosidase due to inactivation of the gene. In the presence of a chromogenic substrate, non-recombinants form blue colour colonies and recombinants form colourless colonies.

pBR322 Plasmid

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