Friday, June 8, 2007
Principle of GM food*Inserting genes
When a plant, for example, is modified by inserting a gene from another plant into it, this is the process:
1. A plant that has the desired characteristic is identified.
2. The specific gene that produces this characteristic is located and cut out of the plant’s DNA.
3. To get the gene into the cells of the plant being modified, the gene needs to be attached to a carrier. A piece of bacterial DNA called a plasmid is joined to the gene to act as the carrier.
4. A type of switch, called a ‘promoter’, is also included with the combined gene and carrier. This helps make sure the gene works properly when it is put into the plant being modified. Only a small number of cells in the plant being modified will actually take up the new gene. To find out which ones have done so, the carrier package often also includes a marker gene to identify them.
5. The gene package is then inserted back into the bacterium, which is allowed to reproduce to create many copies of the gene package.
6. The gene packages are then transferred into the plant being modified. This is usually done in one of two ways:
- by attaching the gene packages to tiny particles of gold or tungsten and firing them at high speed into the plant tissue. Gold or tungsten are used because they are chemically inert – in other words, they won't react with their surroundings
- by using a soil bacterium, called Agrobacterium tumefaciens, to take it in when it infects the plant tissue. The gene packages are put into A. tumefaciens, which is modified to make sure it doesn't become active when it is taken into the new plant.
7. The plant tissue that has taken up the genes is then grown into full size GM plants.
8. The GM plants are checked extensively to make sure that the new genes are in them and working as they should. This is done by growing the whole plants, allowing them to turn to seed, planting the seeds and growing the plant again, while monitoring the gene that has been inserted. This is repeated several times.
*Altering genes
Genetic modification does not always involve moving a gene from one organism to another. Sometimes it means changing how a gene works by 'switching it off' to stop something happening. For example, the gene for softening a fruit could be switched off so that although the fruit ripens in the normal way, it will not soften as quickly. This can be useful because it means that damage is minimised during packing and transportation. Controlling this gene 'switch' may also allow researchers to switch on modified genes in particular parts of a plant, such as the leaves or roots. For example, the genes that give a plant resistance to a pest might only be switched on in the bit of the plant that comes under attack, and not in the part used for food.
I loved you at Friday, June 08, 2007
