Here�s how it looks in real life.  Leaves (upper left) are cut up.  This wounds them and causes them to release the chemicals that stimulate the bacterium to transfer DNA.  The leaf pieces are dipped in a bacterial suspension, then a couple of days later, they�re transferred to a medium that contains an antibiotic to eliminate the bacteria and a compound that permits only the cells that received the agrobacterial DNA to grow.  The medium also contains some plant hormones that stimulate the cells to grow as a disorganized mass called a callus, which is like the tumor on the plant (upper right). But the miracle of plants is that if you take away those growth hormones, the callus begins to form leaves and shoots (lower left). These grow bigger (lower right)  and eventually sprout roots, and grow into a normal plant, now carrying a new gene in all of its cells.