Figure 1. Gene transfer by means of the Ti-plasmid of Agrobacterium tumefaciens. Not the whole plasmid but the T-region is transferred into the nucleus. The signals for transfer of the T-region are located in the areas marked in black. Foreign genes (in red) are inserted into the green area. These genes arrive in the nucleus, where they are inserted into one of the chromosomes. The steps depicted are: isolation of the Ti-plasmid, insertion of genes to be transferred, transformation of A. tumefaciens, and transfer of the T-region. (Drawing: Anne Kemmling, Goettingen, Germany.)