As per the request of the United Nations committee, John, Mike, and myself have prepared a brief primer on genetic engineering itself and its applications in the field of agriculture. This briefing sheet will concern itself with agricultural applications not in terms of the uses of genetic engineering to alter plants, but as concerns the physical act of genetically engineering the plants - how the DNA is transferred, etc. To begin with, it should be pointed out that it is easier to genetically alter plant cells than to alter animal cells. Plant cells can rediffererentiate (i.e. a transformed piece of leaf could be regenerated into a whole plant), plant transformation and regeneration are fairly easy for a number of plants, and plants already contain a natural method of transformation in the bacterium Agrobacterium tumefaciens.

This bacterium contains the main method of genetic modification. When placed into contact with a cell, the bacterium transfers a Ti plasmid to the cell which randomly integrates itself into the cell chromosome. The integrated part contains genes for synthesis of food for the bacterium and plant hormones. Scientists merely ãdisarmä the plasmid by deleting the gene which codes for bacterium food production and replace it with a marker gene, typically for antibiotic resistance or the like. Any gene which scientists wish to transfer could theoretically be inserted as well. It goes without saying that there are limits - a gene from a herring for quicker eye reflex movement would be quite useless in a tomato, which has no tissue necessary for eyes. However, a gene from an Alaskan herring which helps it survive the cold of Arctic waters would be useful in a tomato, as it could help it survive a sudden cold snap and extend the growing season. And yes, I realize this is not the most exciting material - weâre talking about plant bacteria. Bear with me.

While the bacterium method is frequently successful, it has limits. Monocots (grasses and corn, for example) have shown difficulty in transformation through this method. For genetically improved corn, another increasingly common method of gene transfer is to coat tiny mm-sized bullets with the particular DNA and then fire them into the cells from a device similar to a shotgun. The ãgene gunä has been shown to work with DNA transfer to chloroplasts as well as the plant cells themselves. This method of DNA delivery works exceptionally well and on virtually all species of plants, and has been used with great success in the past several years to transform rice in developing countries such as China http://photoscience.la.asu.edu/photosyn/courses/BIO_343/lecture/geneng.html.

Another method which does not seem to enjoy as much popular support at this time except in cereals is electroporation. In this particular method, a jolt of electricity is used to puncture self repairing holes in protoplasts (i.e. the cell without the cell wall). DNA is allowed to get in through these holes. One of the reasons it doesnât seem to enjoy much support is the fact that chemically, it is very difficult to generate fertile plants from cereal protoplasts. It seems that advances have been made in overcoming these difficulties, allowing even the creation of entire transgenic trees, identical to their predecessors with the exception of being resistant to some particular virus or other http://photoscience.la.asu.edu/photosyn/courses/BIO_343/lecture/geneng.html. Ah, what an age we live in - the wonders of genetic engineering are clearly visible to all who would abound in its splendor. Hurrah for science, woo!

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