In gene cloning projects, plasmids primarily function to:

• A. Replace the host chromosome so the inserted gene becomes the only genetic material
• B. Provide ribosomes and tRNAs required for translating cloned genes into protein
• C. Act as restriction enzymes that cut DNA at specific recognition sites
• D. Serve as vectors that carry foreign DNA into a host cell where it can be replicated

Answer: (D)

Verified step by step guidance

1. Understand the role of plasmids in gene cloning: Plasmids are small, circular DNA molecules separate from the chromosomal DNA in bacteria.
2. Recognize that plasmids are used as vectors, meaning they carry foreign DNA into a host cell.
3. Know that once inside the host cell, plasmids replicate independently, allowing the inserted gene to be copied along with the plasmid.
4. Distinguish plasmids from other components: they do not replace the host chromosome, provide ribosomes or tRNAs, nor act as restriction enzymes.
5. Conclude that the primary function of plasmids in gene cloning is to serve as vectors that carry foreign DNA into a host cell where it can be replicated.