Biotechnology: Principles and Processes — BIOLOGY STD 12 Science — Question

After gaining knowledge from bacteria and viruses, gene cloning was done in plants and animals also. Some types of bacteria and viruses were studied which are pathogens in plants and animals. For example, Agrobacterium tumifaciens is a pathogenic pathogen of many dicotyledonous plants. It transforms normal plant cells into tumors by transferring a segment of DNA called 'TDNA' and these tumor cells produce chemicals necessary for the pathogen. In the same way, retroviruses in animal cells transform normal cells into cancer cells. By understanding the art of gene transfer by pathogens in their eukaryote host, they can use this knowledge to transform these tools of pathogens into useful vectors for delivering genes of interest to humans. The Ti plasmid of Agrobacterium tumifaciens has now been adapted as a cloning vector that is not pathogenic to plants, but is used to transfer genes of interest to many plants. In the same  way, retrovirus is made harmless and used to modify desired genes in animal cells. In this way, when a gene or segment of DNA is attached to the appropriate vector, it is transferred to the bacterial, plant or animal host (where it continues to multiply).