Benefits and risks of GM crops

Genetically modified (GM) crops have had their genes modified to give them desired characteristics. These characteristics can help farmers reduce crop losses or improve the quantity and quality of the food produced.

Benefits of GM crops

A GM crop may be made resistant to disease or insect attack. If fewer plants are damaged or lost, more of the crop can be harvested. A crop may also be made resistant to a herbicide, allowing the herbicide to be used against unwanted plants without damaging the crop.

Other modifications can produce larger or better-quality fruits. By reducing losses or improving production, GM crops generally give increased yields: more crop is harvested from the same area of land.

Risks and concerns about GM crops

Changes in how a GM crop is grown can affect organisms beyond the crop itself. For example, herbicide use may reduce wild flower populations in and around fields. Insects that depend on those plants for food or habitat may then also be affected.

Some people also question whether the effects of eating GM crops on human health have been fully explored. A concern about a possible effect, however, does not by itself establish that harm occurs.

Genetic engineering

Genetic engineering changes an organism’s genome—its complete set of genetic material—to give it a desired characteristic. One way to do this is to introduce a gene from another organism. The introduced gene can be expressed in the recipient’s cells: the cells use its instructions to make a protein that produces the desired characteristic.

Transferring a gene

The required gene is first isolated from a chromosome using enzymes that cut DNA. Other enzymes are then used to insert the gene into a vector, which carries it into the required cells. A vector can be a bacterial plasmid, a small circular piece of DNA, or a virus.

Cells of animals, plants or microorganisms can be genetically modified at an early stage. As the modified cells divide, the gene is passed to cells derived from them. These cells can express the gene, allowing the organism to develop with the desired characteristic.

Insulin production using genetically engineered bacteria

Bacteria can be given a human gene containing the instructions for making insulin. The gene is inserted into the bacteria’s DNA. The bacteria are then grown and express the gene, using its instructions to produce human insulin.

The insulin is collected and purified to remove bacterial material and other impurities. It is also checked before being used to treat people with diabetes, because contamination or impurities could harm patients.

Large numbers of bacteria can be grown to produce insulin in large quantities. This provides a supply without relying on insulin extracted from animal organs. It is the bacteria, not the patient’s cells, that are genetically modified.

Genetic modification for inherited disorders

Some inherited disorders are caused by a faulty gene that prevents cells from making a functional protein. Genetic modification is being explored as a treatment for some of these disorders by introducing a working copy of the gene into affected cells.

If the introduced gene works in those cells, it can provide the instructions for making the functional protein. This may reduce the effects of the disorder. The treatment aims to address the effects of the faulty gene; it does not necessarily remove or repair that gene.

Limitations and risks of genetic modification

A working gene must reach enough of the relevant cells to make a useful difference. Even if it does, its effect may not last. A delivery vector is used to carry the gene into cells, but the body may react to the vector, causing an immune reaction. Genetic modification can also cause unintended changes to DNA.

Genetic modification of embryos

Some people object to modifying embryos because the changes could be inherited by future generations. Those generations would also be affected by consequences that may be uncertain in the long term.