In the context of recombinant DNA technique, what does the term "vector" refer to?

Plasmid responsible for transferring DNA into the host cell

The correct answer is Option (2) - Plasmid responsible for transferring DNA into the host cell.

In recombinant DNA technology, a vector refers to a carrier molecule, often a small DNA molecule, used to transfer a specific piece of DNA (the donor DNA) into the host cell. Plasmids are commonly used as vectors in genetic engineering because they can replicate independently within the host cell and can carry foreign DNA inserts.

When the donor DNA (the DNA fragment of interest) is joined with the vector, the resulting DNA construct is called recombinant DNA. This recombinant DNA can then be introduced into the host cell using various methods, to produce genetically modified organisms (GMOs) or to produce desired proteins for research and other applications.