Genetic Engineering.

Genetic engineering (GE) is used to take genes and segments of DNA from one species, e.g. fish, and put them into another species, e.g. tomato. To do so, GE provides a set of techniques to cut DNA either randomly or at a number of specific sites. Once isolated one can study the different segments of DNA, multiply them up and splice them (stick them) next to any other DNA of another cell or organism. GE makes it possible to break through the species barrier and to shuffle information between completely unrelated species; for example, to splice the anti-freeze gene from flounder into tomatoes or strawberries, an insect-killing toxin gene from bacteria into maize, cotton or rape seed, or genes from humans into pig.

Yet there is a problem - a fish gene will not work in tomato unless I give it a promoter with a "flag" the tomato cells will recognise. Such a control sequence should either be a tomato sequence or something similar. Most companies and scientists do a shortcut here and don't even bother to look for an appropriate tomato promoter as it would take years to understand how the cell's internal communication and regulation works. In order to avoid long testing and adjusting, most genetic engineering of plants is done with viral promoters. Viruses - as you will be aware - are very active. Nothing, or almost nothing, will stop them once they have found a new victim or rather host. They integrate their genetic information into the DNA of a host cell (such as one of your own), multiply, infect the next cells and multiply. This is possible because viruses have evolved very powerful promoters which command the host cell to constantly read the viral genes and produce viral proteins. Simply by taking a control element (promoter) from a plant virus and sticking it in front of the information block of the fish gene, you can get this combined virus/fish gene (known as a "construct') to work wherever and whenever you want in a plant.

This might sound great, the drawback though is that it can't be stopped either, it can't be switched off. The plant no longer has a say in the expression of the new gene, even when the constant involuntary production of the "new" product is weakening the plant's defences or growth.

And furthermore, the theory doesn't hold up with reality. Often, for no apparent reason, the new gene only works for a limited amount of time and then "falls silent". But there is no way to know in advance if this will happen.

Though often hailed as a precise method, the final stage of placing the new gene into a receiving higher organism is rather crude, seriously lacking both precision and predictability. The "new" gene can end up anywhere, next to any
gene or even within another gene, disturbing its function or regulation. If the "new" gene gets into the "quiet" non-expressed areas of the cell's DNA, it is likely to interfere with the regulation of gene expression of the whole region. It could potentially cause genes in the "quiet" DNA to become active.

Often genetic engineering will not only use the information of one gene and put it behind the promoter of another gene, but will also take bits and pieces from other genes and other species. Although this is aimed to benefit the expression and function of the "new" gene it also causes more interference and enhances the risks of unpredictable effects.