he Bascillus thuringiensis. It is made radioactive and when inserted into the bacteria it hybridises (attaches to the complementary base pairing) with the DNA sequence that codes for the Bt protein. The DNA binding to the probe becomes radioactive so it can be detected by x-ray film.Fig. 3 DNA probe productionThe gene is then isolated from the bacterium by using restriction enzymes and multiplyed in the bacterium E. coli through gene cloning. The gene is first inserted into a plasmid from E. coli containing a gene coding for resistance to the antibiotics kanamycin and neomycin. The plasmid is cut with the same restriction enzyme as used to cut the Bascillus thuringiensis’ DNA. The restriction enzyme cuts both the DNA and the plasmid leaving sticky ends on the resulting fragments that enable the Bt gene to be incorporated into the plasmid. The complementary ends pair and the enzyme DNA ligase is used to join them together. Fig. 4 Bt gene insertion into E. coli plasmid The plasmid is then introduced into the E. coli cells by transformation. The E. coli cells that take-up the new plasmid then can be identified by their resistance to the antibiotics kanamycin and neomycin. The E. coli replicates the plasmids so that a single cell may contain hundreds of identical copies. After the plasmids containing the Bt gene have been multiplied the Bt toxin gene is then isolated again and is inserted into a plasmid of the bacterium Agrobacterium tumafacien using the same techniques as used to insert the Bt gene into the E. coli. This plasmid is then put back in the Agrobacterium, which transfers the Bt gene into the cotton plant cell. The bacteria does this by infecting the plant cell causing a tumor to form and while infecting the plant part of the plasmid is transferred into the plant’s nucleus.Fig. 5 Bt gene insertion into cotton plant cell Biological implications of genetically engineering cotton for insect resistanceThe tra...
