Cloning and expression vectors

• The vectors used for propagation of DNA inserts in a suitable host are called cloning vectors.
• When a vector is designed for the expression of i.e., production of the protein specified by, the DNA insert, it is known as expression vector.
• The most common vector include: Plasmids, Cosmids, Phasmids, Phages, Transposons, Bacterial chromosome, etc.

A. Plasmid:

• Extrachromosomal DNA.
• Bacterial small circular double stranded DNA molecule.
• Replicate independently on host cells.
• Common plasmid vectors are pBR322, pUC, Ti & Ri plasmid

B. Cosmid:

• Contain Cos site of DNA.
• Add advantages of phage to plasmid vector.
• Cloning large segments of foreign DNA

C. Phasmid:

• Contain fragment of phage DNA.
• Contain att site.

D. Phase vector:

• Contain many target site in DNA.