Which statement about plasmid vectors is true?

• A. They are DNA carriers that deliver genetic material into a host cell
• B. They are enzymes that cut DNA at specific sequences
• C. They are nutrients that promote growth
• D. They are proteins that protect cells from viruses

Answer: (B)

Plasmid vectors are DNA carriers that deliver genetic material into a host cell. They are circular DNA molecules engineered to carry the gene of interest and to replicate inside the host due to an origin of replication, making them tools for cloning and gene expression. They are not enzymes; enzymes that cut DNA at specific sequences are restriction enzymes, which are separate tools used to cut DNA, not to carry or deliver it. Nutrients or protective proteins described in the other options don’t capture the role of a plasmid vector in genetic engineering.