Which tool is useful for cutting a vector in cloning?

Correct answer: Restriction enzyme

The direct answer is option A: restriction enzyme. In cloning, a vector is a DNA molecule used to carry a desired gene into a host cell. To insert the gene, scientists first cut the vector at a suitable restriction site. A restriction enzyme recognises a specific DNA sequence and cuts the DNA there, producing ends that can be joined with the insert, often with matching sticky ends. This is why the enzyme is often called molecular scissors. Option A is correct because it directly cuts the vector DNA at a planned site. Option B, a ribosome, reads messenger RNA and helps make proteins; it does not cut DNA. Option C, a chloroplast, is a photosynthetic cell organelle, not a DNA-cutting tool used for opening a vector. Option D, a lysosome, contains digestive enzymes that break down materials inside cells; it is not the specialised laboratory tool for cutting a cloning vector. After cutting, DNA ligase is commonly used to join the insert and vector, but ligase is not one of the options and is not the cutting tool. Memory cue: restriction enzyme cuts; DNA ligase joins.