A genetically modified organism (GMO) is an animal, plant, or microbe whose DNA has been altered using genetic engineering techniques.

For thousands of years, humans have used breeding methods to modify organisms. Corn, cattle, and even dogs have been selectively bred over generations to have certain desired traits. Within the last few decades, however, modern advances in biotechnology have allowed scientists to directly modify the DNA of microorganisms, crops, and animals.

Conventional methods of modifying plants and animals—selective breeding and crossbreeding—can take a long time. Moreover, selective breeding and crossbreeding often produce mixed results, with unwanted traits appearing alongside desired characteristics. The specific targeted modification of DNA using biotechnology has allowed scientists to avoid this problem and improve the genetic makeup of an organism without unwanted characteristics tagging along.

Most animals that are GMOs are produced for use in laboratory research. These animals are used as “models” to study the function of specific genes and, typically, how the genes relate to health and disease. Some GMO animals, however, are produced for human consumption. Salmon, for example, has been genetically engineered to mature faster, and the U.S. Food and Drug Administration has stated that these fish are safe to eat.

GMOs are perhaps most visible in the produce section. The first genetically engineered plants to be produced for human consumption were introduced in the mid-1990s. Today, approximately 90 percent of the corn, soybeans, and sugar beets on the market are GMOs. Genetically engineered crops produce higher yields, have a longer shelf life, are resistant to diseases and pests, and even taste better. These benefits are a plus for both farmers and consumers. For example, higher yields and longer shelf life may lead to lower prices for consumers, and pest-resistant crops means that farmers don’t need to buy and use as many pesticides to grow quality crops. GMO crops can thus be kinder to the environment than conventionally grown crops.

Genetically modified foods do cause controversy, however. Genetic engineering typically changes an organism in a way that would not occur naturally. It is even common for scientists to insert genes into an organism from an entirely different organism. This raises the possible risk of unexpected allergic reactions to some GMO foods. Other concerns include the possibility of the genetically engineered foreign DNA spreading to non-GMO plants and animals. So far, none of the GMOs approved for consumption have caused any of these problems, and GMO food sources are subject to regulations and rigorous safety assessments.

In the future, GMOs are likely to continue playing an important role in biomedical research. GMO foods may provide better nutrition and perhaps even be engineered to contain medicinal compounds to enhance human health. If GMOs can be shown to be both safe and healthful, consumer resistance to these products will most likely diminish.