Vector is an agent that carries and transmits an infectious pathogen into another living organism; a disease vector. Vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell. Cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes Shuttle vector is a plasmid constructed so that it can propagate in two different host species. Viral vector is a tool commonly used by molecular biologists to deliver genetic materials into cells.