Which of the following statements is correct regarding Agrobacterium tumefaciens and T-DNA transfer?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → All of the above.
Agrobacterium tumefaciens is a soil bacterium that causes disease in many dicot plants. Its Ti (tumour-inducing) plasmid passes a piece of DNA, the T-DNA, into the plant cell and turns normal cells into tumour cells.
Option (1) Tumour formation is induced by the Ti (tumour-inducing) plasmid. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The Ti plasmid is the plasmid that induces the tumour.
Option (2) The transfer of T-DNA into plant cells causes tumour formation. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The T-DNA turns normal plant cells into a tumour.
Option (3) Agrobacterium tumefaciens, a soil-inhabiting plant bacterium and a pathogen of several dicot plants, is capable of transferring a piece of DNA known as T-DNA. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. The bacterium is a pathogen of several dicot plants and can deliver T-DNA.
NCERT Extract:
Cloning Vectors – “… For example, Agrobacterium tumifaciens, a pathogen of several dicot plants is able to deliver a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen. … The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants.”