ltered organism. In most cases the splicing involves recombining the donor’s desirable genes with the DNA from a “vector”, which will carry the donor DNA into the host. Many times the host will be a bacterium, which will reproduce and multiply the recombinant DNA producing large quantities of the desired protein. In some cases, DNA can be introduced directly into an organism by injection into reproductive cells. (Encarta, 1999) The most commonly used plant-cloning vector is the “Ti” plasmid; otherwise know as the tumor-inducing plasmid. This plasmid may be found in cells of the bacterium known as Agro bacterium tumefaciens lives in soil. This bacterium has the ability to infect plants causing a tumorous lump called a crown gall, which forms at the site of infection. The studied plasmid is a large, circular, double-stranded DNA molecule that can replicate independently of the genome. When the bacteria infect a plant cell a 30,000 base pair segment of the Ti plasmid separates from the plasmid and incorporates into the host cell genome. “This aspect of Ti plasmid function has made it useful as a plant cloning vector”. (Peters) One of the earliest experiments that involved the transport of a foreign gene by the Ti plasmid involved the insertion of a gene isolated from a bean plant into a host tobacco plant. This experiment may have served no commercially useful purpose but it successfully established the ability of the Ti plasmid to carry genes into plant host cells, where they could be incorporated and expressed. Unfortunately many important crop plants, such as corn, rice and wheat, are monocotyledons, plants with one embryonic leaf, which cannot be transected using this form of bacteria. Supporters of Genetic Engineering see genetic engineering as the “way of the future, an unstoppable force that will feed the mounting millions of the Third World, increase yields, reduce relian...
