In genetic engineering a gene is taken from one organism and put into another so that the second organism has a new characteristic. An organism that has been changed in this way is a genetically modified (GM) organism. A well known example is a gene taken from the bacterium Bacillus thuringiensis that makes a protein poisonous to certain insects. When this gene is put into a crop plant such as maize or cotton, the plant makes the insect poison itself and is resistant to insect pests.
The advantages are that the crop suffers less damage, so the yield can be higher, and farmers need to spray less insecticide. This saves money and may reduce harm to other insects and to the environment. Crops can also be modified to be more nutritious or to grow in poor conditions, which helps to feed a growing population.
There are also disadvantages and concerns. Some people worry that eating GM food may be harmful to health, although there is no strong evidence for this. Genes might spread to wild plants by pollination, for example making weeds resistant. Insect pests may evolve resistance to the poison, and harmless insects might be harmed. GM seed can also be expensive, and seed companies may own the rights, so farmers must buy new seed each year.