I don’t understand how the gene for resistance came from A. Tumefaciens as it was not present from first place before its addition
Hi,
Gene for resistance does not come from A. Tumefaciens. Instead, gene for resistance, that is extracted from somewhere else, is added to the disarmed DNA Plasmid extracted from A Tumefaciens, so that it can “infect” the target plant. As A. Tumefaciens has the ability to grow and multiply rapidly, it will naturally transfer gene for resistance to the target plant when it infects the plant.