Southern Analysis of Transgenic Tobacco Plants

Southern analysis (1 ) is routinely carried out to determine whether a plant regenerated from tissue-culture has been transformed with foreign DNA. The technique of Southern analysis begins with the extraction of genomic DNA from the plant, digestion of the DNA with diagnostic-restriction enzymes, and fractionation of the restricted DNA by agarose gel electrophoresis. Following the transfer of the fractionated DNA to a nylon membrane by capillary blotting (Southern blotting), a radioactively labeled fragment of the foreign DNA is used for the detection of homologous sequences within the plant genomic DNA. This technique allows not only the detection of foreign DNA, but also an estimation of the number of copies and the arrangement of the foreign gene(s) within the plant genome.