Final answer:
The Ti plasmid of Agrobacterium tumefaciens contains genes that cause the formation of a plant tumor, or a gall, in infected tissues. The Ti plasmid carries a gene that codes for the production of a plant growth substance called cytokinin which is involved in the cell proliferation required for gall formation.
Step-by-step explanation:
The Ti plasmid of Agrobacterium tumefaciens contains genes that cause the formation of a plant tumor, or a gall, in infected tissues. When A. tumefaciens infects a plant, it transfers its Ti plasmid into the plant cell's genome. Among other genes, the Ti plasmid carries a gene that codes for the production of a plant growth substance called cytokinin, which is involved in the cell proliferation required for gall formation.