What is GM?
Genetic modification (GM) involves the artificial insertion of a foreign gene into the genetic material of an organism in an essentially random way.
There are currently two main types of genetically modified crops, those engineered to be resistant to herbicides in order to kill weeds and those engineered to produce toxins to kill pests.
GM crops were first grown in 1996 in the US. Three quarters of the world's GM crops are now grown in the US and Canada. The main GM crop in the US is soya and maize and in Canada it is oilseed rape.