Cis-genic vs Trans-genic – What’s the difference and why you should know about it…
In a previous blog “GM is not new: Frankenplants and Frankenfoods”, I discussed how crop plants have been changed by either selecting plants that have been changed by natural mutations or by enhanced mutations using ionizing radiation or mutagens. This has been very successful in enhancing the yield of the crops we grow today and without it a world population of 7 billion could not have been supported. 
However, when we use these procedures, we do not know precisely what has been changed at the molecular level. Modern molecular technologies now are beginning to determine what genes were changed, as for example the gene that caused Mendel’s peas to be round or wrinkled.
Designer genes, know your brands tech…
Traditional breeding techniques usually change more than one gene and we have no idea what effect this might have had, although many tests are now done to try to eliminate negative effects. Would it not be better if we knew the gene that had to be altered and could very precisely change that gene alone to produce the crop we wanted? Our knowledge now of the DNA of crop plants and the function of most of the genes it contains, now makes this a reality.
There are two ways this can be achieved. A gene that has been isolated from a different species or organism can be successfully transferred to the crop plant that we wanted to alter. Crops that have been changed by this biotechnology are grown in many countries of the world. This is known as transgenic modification. So far, it has been used successfully to produce insect and herbicide resistance plants by inserting bacterial genes into the plants.
It has been suggested that the technology for altering a plant’s own genes should be called cis-genic modification rather than trans-genic…
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What is even more exciting is that once the gene has been found in one species of plant, one can look for the same gene in other species and change them in the same way. One doesn’t have to go all through the selection process from the beginning as we have had to do with traditional breeding. We can simply find the gene in the new species and change it to produce the characteristics we desire, all with little damage to the rest of genome and at a fraction of the time.
But you need more than one gene to change a plant – don’t you?
I have been told on a number of occasions that one needs more than one gene to change a plant. This is often true but it fails to recognize that there are two types of genes in all higher organisms. The first type of gene codes for proteins which are essential for all that reactions that take place in cells. The second type acts to control the activity of protein coding genes and can turn banks of them on or off. It is therefore possible to affect several genes by altering a single controlling gene. We now know that it was changes in this type of gene modified by selection that made the Green Revolution possible.
It has been suggested that the technology for altering a plant’s own genes should be called cis-genic modification rather than trans-genic where plants are modified by transferring genes between different species. Transgenic technology is the only form of genetic modification that we only hear about and is in use commercially. I will deal with this form of modification in a later blog. However, there is no doubt in my mind that, in future, cisgenic technology will be the one that will be mainly used to develop new crop varieties.
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