Question

Which one of the following microorganisms is used as a cloning vector to deliver the genes of interest into a variety of plants?

• A. Bacillus thuringiensis
• B. Rhino viruses
• C. Agrobacterium tumifaciens
• D. Nucleopolyhedrovirus

Hint:

Think of the Ti plasmid and crown gall disease.

Answer 1

The Correct Option is C

Step 1: Understand the Concept:
A cloning vector carries a foreign gene into a host cell. For plants, a natural gene carrier is needed that can insert DNA into the plant genome.

Step 2: Check option 1:
Bacillus thuringiensis makes the Bt toxin protein. Its gene is used in crops, but the bacterium is not the vector. So option 1 is wrong.

Step 3: Check option 2:
Rhino viruses cause the common cold in humans. They are not used as plant vectors. So option 2 is wrong.

Step 4: Check option 3:
Agrobacterium tumefaciens is a soil bacterium that causes crown gall disease. Its Ti plasmid transfers T-DNA into plant cells. Scientists disarm the Ti plasmid and use it to deliver useful genes into many plants. So option 3 is right.

Step 5: Check option 4:
Nucleopolyhedrovirus is a baculovirus that infects insects. It is used as a biocontrol agent, not as a plant vector. So option 4 is wrong.

Final Answer:
Agrobacterium tumefaciens is the cloning vector for plants, which is option 3. \[ \boxed{3} \]