In genetic engineering, which molecule is commonly used as the carrier of foreign DNA into a host organism?

• A. Lipid
• B. Enzyme
• C. Plasmid
• D. Polymerase

Answer: (A)

The key idea is that a vector is used to move foreign DNA into a host cell, and plasmids are the classic carriers for this purpose. A plasmid is a small, circular piece of DNA that can exist independently of the host’s chromosome. It can be engineered to carry a gene of interest along with regulatory elements that drive its expression. Because plasmids replicate inside the host and often include selectable markers, they make it straightforward to identify and propagate cells that have taken up the foreign DNA. While other delivery methods, like certain lipid-based systems, are used in some contexts, the standard tool in genetic engineering for introducing recombinant DNA is the plasmid. Enzymes and polymerases are involved in processing DNA, not delivering it into cells, so they don’t serve as carriers in this sense.