Which of the following statement is incorrect?

pBR322 is a natural plasmid

The correct answer is Option (2) – pBR322 is a natural plasmid.

Explanation:

(1) In microinjection method, foreign DNA is indeed directly injected into the nucleus of an animal cell using microneedles. This is a technique used in genetic engineering to introduce foreign DNA into animal cells.

(2) pBR322 is not a natural plasmid. It is an artificial or synthetic plasmid that was created in the laboratory for use as a cloning vector in genetic engineering experiments.

(3) Agrobacterium tumefaciens is considered a natural genetic engineer because of its ability to transfer a piece of DNA called T-DNA into the cells of certain plants. This T-DNA transfer mechanism is widely used in genetic engineering to introduce genes of interest into plant cells.

(4) Tumour formation is indeed induced by Ti plasmid. Agrobacterium tumefaciens carries a Ti (tumour-inducing) plasmid, which contains the T-DNA responsible for causing tumour formation in infected plants. The T-DNA is transferred to the plant cells, leading to the development of tumours or galls.