Q.Draw the structure of pBR 322.

pBR322 is a circular E. coli cloning vector of about 4361 bp carrying an origin of replication, ampR and tetR resistance marker genes, and unique restriction sites used to detect recombinants by insertional inactivation.

pBR322 is one of the earliest and most widely used plasmid cloning vectors, constructed for use in the bacterium E. coli. Its key structural features are:

1. Size: a small, circular, double-stranded DNA molecule of about 4361 base pairs (4.36 kb).
2. Origin of replication (ori): a specific DNA sequence that allows the plasmid to replicate independently inside the host bacterial cell and be maintained/multiplied across generations.
3. Two antibiotic-resistance marker genes:
   • ampR (ampicillin-resistance gene) -- confers resistance to the antibiotic ampicillin.
   • tetR (tetracycline-resistance gene) -- confers resistance to the antibiotic tetracycline. These two markers allow selection of bacterial cells that have successfully taken up the plasmid (they will grow on media containing these antibiotics, while cells without the plasmid will not). …