Question

The ability to transform a normal cell into a cancerous cell is found in

• A. Any plasmid
• B. Ti plasmid
• C. Retrovirus
• D. Both (b) and (c)

Answer 1

The correct option is D Both (b) and (c)

Ti-plasmid (tumor-inducing) is present in the Agrobacterium species. This is a naturally occurring gram-negative bacterium that causes crown gall disease in plants with the help of Ti-plasmids. Ti-plasmid is a low copy number, large plasmid which contains the T-DNA (transfer-DNA) region. The left and right border sequences are necessary for the transfer process but they are not integrated into the plant genome.
The T-DNA carries genes for auxin, cytokinin, and opines overproduction of these in the infected cell causes the cell to proliferate which leads to the formation of gall (tumor). This is the reason it is considered as a natural genetic engineer.
Certain retrovirus causes cancer by their ability to cause mutation in the host-specific gene. Thus both Ti-plasmid and retrovirus have the ability to transform a normal cell into a cancerous cell.