A plasmid may be used as a vector. Explain what is meant by a vector.

• A. Carrier of DNA / gene into another cell/host
• B. A bacterial enzyme that cuts DNA
• C. A virus that infects cells
• D. A nutrient molecule used by cells

Answer: (A)

A vector in genetic engineering is a DNA vehicle used to move a gene into a host cell. A plasmid fits this role because it’s a small circular DNA molecule that can replicate independently in bacteria and be engineered to carry foreign DNA. When the gene of interest is inserted into the plasmid and the plasmid is introduced into a host cell, the cell can replicate the plasmid and often express the inserted gene. Plasmids are designed with features like an origin of replication and selectable markers to help identify cells that have taken up the plasmid, making them practical carriers for delivering DNA. The other options describe different things—a DNA-cutting enzyme, a viral vector, or a nutrient molecule—not the function of a plasmid as a DNA delivery vehicle.