Diabetes is a disorder in which the body's blood glucose levels remain too low or too high. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up by the liver and other tissues, which results in cells receiving the glucose they need, and blood glucose levels stay normal.
Bacterial cells have been genetically modified to produce substances such as human insulin.
Current genetically modified crops include those that are resistant to insect attack or are herbicide resistant, this produced increased yields. Herbicide resistant crops allow them to tolerate the herbicide, but the weeds are killed by it, thus overall less herbicide is needed.
Scientists have added a gene to wild rice that makes it produce beta carotene. This changes the colour of the wild rice to a golden colour. Beta carotene is needed by humans in order to make vitamin A - which is essential for good vision.
The advantage of golden rice is that it can be used in areas where vitamin A deficiency is common, so it can help prevent blindness. In many countries golden rice is not being grown commercially over fears associated with genetically modified crops.
There are ethical issues involved in genetic modification, as well as concerns about the possible health risks of genetically modified food. For example, a GM food might contain a substance that causes an allergic reaction in some people, or higher levels of a toxin naturally found in the food. Others think it is ethically wrong to create new life forms, or to move genes between different species.
In the future researchers are hoping to use genetic engineering to be able to overcome some inherited disorders, such as cystic fibrosis and Huntington's disease amongst others.