Explain the vector map of:

pBR322

pBR322 is a plasmid and one of the first widely used E.coli cloning vectors. It was named after the researcher who constructed it "Bolivar" and "Rodriguez".

• It is 4361 base pairs in length.
• It has two antibiotic resistance genes- the gene bla encoding the ampicillin resistance (AmpR) protein, and the gene tetA encoding the tetracycline resistance (TetR) protein.
• It contains the origin of replication of pMB1, and the rop gene, which encodes a restrictor of plasmid copy number.
• It has unique restriction sites for more than forty restriction enzymes (11 out of 40 sites lie within TetR gene), (2 sites for restriction enzyme- Hind III and Cla I are at promoter of TetR gene). There are 6 restriction sites inside the AmpR gene.
• The circular sequence is numbered such that O is the middle of the unique EcoRI site and the count increases through the TetR gene.
• The AmpR gene is penicillin beta-lactamase. Promoters P1 and P3 are for the beta-lactamase gene.
• P3 is the natural promoter and P1 is artificially created by the ligation of two different DNA fragments to create pBR322.
• P2 is in the same region as P1, but it is on the opposite strand and initiates transcription in the direction of tetracycline resistance gene.
• Copy number- 1-100 per cell.

pUC:

pUC is one of the series of plasmid cloning vectors. "p" prefix denoting plasmid and the abbreviation UC for the University of California, where early work on the plasmid series had been conducted.

• It is a circular double stranded DNA and has 2686 base pairs.
• It has one ampR gene (ampicillin  resistance gene) and an N-terminal fragment of beta-galactosidase (lacZ) gene of E.coli.
• The multiple cloning site (MCS) region is split into the lacZ gene (codons 6-7 of lacZ are replace by MCS), where various restriction sites for many restriction endonuclease are present.
• In addition to beta-galactosidase, pUC19 also encodes for an enzyme called beta-lactamase, which can degrade ampicillin and reduces its toxicity to the host.
• The ori site or origin of replication is derived from the plasmid pMB1.
• pUC19 is small but has a high copy number. The high copy number is a result of the lack of the rop gene and a single point mutation in the ori of pMB1.
• The recognition sites for HindIII, SphI, Pst I, Sa II, Xba, BamtII, SmaI, KpnI, SacI and EcoRI restriction enzyme have been derived from the vector M13mp19.
• When the pUC plasmid has been used to transform the host cell E.coli the gene may be switched on by adding the inducer IPTG. Its presence causes the enzyme beta-galactosidase to be produced which will hydrolyze a colorless substance X-gal into a blue soluble material. However if the gene is disrupted by the insertion of a foreign fragment of DNA, a non-functional enzyme results which is unable to carry out the hydrolysis of X-gal. Hence, recombinant can be easily distinguished from the non-recombinants based on the color differences of colonies on growth media.
• pUC vectors carry different combinations of restriction sites and shows greater flexibility in the types of DNA fragment that can be cloned. Clustering of the restriction sites allow a DNA fragment with two different sticky ends to be cloned without involving linker attachment.
• 

pET28a

• Size- 7328 base pairs.
• It has bacterial expression vector with T7 lac promoter, adds N-terminal His tag, thrombin cleavage site, internal T7 epitope tag, C-terminal His tag, restriction enzyme cloning.
• It has antibiotic resistance for kanamycin.
•  pET28a is used for bacterial expression, in vitro transcription, multiple cloning site, with tag/fusion/marker.