Final answer:
The virulence trait of Agrobacterium tumefaciens is borne on the tumor-inducing plasmid DNA (b). In nature, A. tumefaciens has a set of plasmids called Ti plasmids (tumor-inducing plasmids), which contain genes that produce tumors in plants.
Step-by-step explanation:
The virulence trait of Agrobacterium tumefaciens is borne on the tumor-inducing plasmid DNA (b).
In nature, A. tumefaciens has a set of plasmids called Ti plasmids (tumor-inducing plasmids), which contain genes that produce tumors in plants. DNA from the Ti plasmid integrates into the infected plant cell's genome. Researchers manipulate the Ti plasmids to remove the tumor-causing genes and insert the desired DNA fragment for transfer into the plant genome.