There are a number of techniques involved in the introduction of new genes into plants. Biochemical 'scissors' called restriction enzymes are used to cut the strings of DNA in different places and select the required genes. These genes are usually then inserted into circular pieces of DNA (plasmids) found in bacteria. The bacteria reproduce rapidly and within a short time, thousands of identical copies and the new gene can be made. The plasmids are then introduced into individual plant cells to produce a "transgenic" or genetically modified (GM) plant.

Before the new gene is transferred, a 'marker gene' is attached which codes for resistance to an antibiotic. Plant cells which have been modified are then grown in a medium containing this antibiotic, and the only ones able to survive are those which have taken up the 'new' genes with the antibiotic-resistant marker attached. These cells are then cultured and grown into mature plants.

A piece of DNA (called a 'promoter') taken from a virus or bacterium is inserted along with the 'new' gene in order to 'switch it on' in its new host. These promoters allow genes to be produced at 10 to 1,000 times normal levels.

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