is the genetic modification of organisms by isolating genes from other plants, bacteria, viruses, and animals (including humans) and inserting them into the embryonic cells of the plant or organism of choice. Unlike conventional crossbreeding, which farmers have used for thousands of years to improve crops and animals, GE crosses special boundaries. For example, broccoli can be crossbred with cauliflower because they're members of the same family, but not with a fish or tomato-at least not until GE came along.
First scientists identify the genes used to control the desired trait. Then, with the help of various chemicals, these genes are extracted from the DNA strands. Next an insertion package is prepared that, in addition to the desired genes, contains promoter genes to keep the desired trait turned on in the host; penetration genes which come mostly from viruses or bacteria, to overpower the host cells' defense mechanism against invasion; and marker genes, which make cells resistant to antibiotics, to help researchers determine successful insertion. The package is then forced into the host's cells using a vector or delivery system, most commonly a bacterium. Retroviruses are often used for mammals; AIDS is a retrovirus. Other methods of insertion include exposing cells to electric fields or inoculating cells with a solution of the desired genes.
(Source:Organic Gardening, January/February, 2000)
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