To understand genetic modification it helps to understand what a gene is. Living organisms inherit characteristics from their parents and genes are one of the factors that determine the characteristics that are passed from one generation to the next. For example, they control what shape pea seeds are and whether a person has brown, blue or hazel eyes. In other words, genes contain information about inherited characteristics.
Genes are parts of chemical molecules called DNA (deoxyribonucleic acid) which are found in all living organisms and carry this genetic information. DNA has a distinctive double helix structure of two strands twisted together. Genes work by coding instructions for making proteins, and proteins are the chemicals that have a strong influence on biological functions. They interact with each other and the environment to produce the characteristics that make different living organisms.
Often the same genes are found in more than one species. Humans have about 35,000 genes but about 99 percent of our genes are shared with chimpanzees and about 80 percent are shared with other mammals such as mice and sheep. We even share some genes with plants and bacteria. Differences in genes, and whether they are turned on or off, create the differences between species.
How it works
As we have seen, genes control the characteristics of living organisms. For thousands of years people have developed plants and animals with the characteristics they want by selectively breeding the best plants and animals.
More recently these conventional breeding methods have included techniques that artificially alter genes (eg, the use of irradiation and chemicals to cause mutations). Most of the crops and domesticated animals on our farms, as well as the plants in our gardens today, are genetically very different from their wild ancestors.
One drawback of trying to improve plants and animals in the conventional way is that it takes a long time, and traditional breeding can never guarantee the presence of a desired characteristic - or the absence of an unwanted characteristic - in the resulting offspring. Genetic modification allows scientists to change genes in a more specific or controlled way. Genes can be switched on or off or their sequences can be altered. By using genetic modification it is possible to introduce new characteristics more quickly. Because all organisms use the same chemical building blocks, copies of genes can be moved between totally unrelated species, making it possible to introduce characteristics that would not be possible through conventional breeding. For example, corn has been genetically modified to produce an insecticide that is made naturally by soil bacteria.
Some people argue that genetic modification is just an extension of the breeding processes we already use to create new varieties. Others believe it is unnatural or inherently unstable, and so completely different from other breeding processes that it raises new ethical, environmental and safety concerns.
What is a genetically modified organism?
A 'genetically modified organism' is a plant, animal, insect or micro-organism whose genetic make-up has been changed using modern laboratory techniques. For example, new genes might have been added or the function of genes already present might have been altered. New genes may contain sequences found in the same or different species or they may be synthetic. A genetically modified organism is a living thing that can grow and reproduce and can pass on its genes (including its modified genes) to its offspring. A living genetically modified corn seed or potato is a genetically modified organism as well as a food. But not all the products we get from genetic modification are living organisms. For example, the flour ground from genetically modified corn seeds is not a living thing, nor is the oil extracted from genetically modified soybeans.
What is biotechnology and how does it differ from genetic modification?
'Biotechnology' refers to any technology that uses living organisms or their products for medical, commercial or industrial purposes. It includes ancient technologies such as using yeast to brew beer as well as modern technologies such as genetic modification.
Genetic modification is just one kind of biotechnology. For example, the following biotechnologies do not generally involve genetic modification:
- tissue culture, used to help grow plant or animal tissues in test tubes for industrial uses and medical research
- bioremediation, where organisms are used to clean up contaminated sites (eg, cleaning up contaminated soils through the use of trees that absorb heavy metals)
- cloning, which creates a genetic copy of something such as a plant (by taking a cutting) or animal (by transferring a copy of its genes into an egg)
- cross-species tissue transplants, or xenotransplantation (eg, using heart valves from pigs for transplantation into humans, a technique that was developed because human tissues or organs for transplant are in relatively short supply).
What can be genetically modified?
Genetically modified bacteria are widely used in research and to produce substances for food and pharmaceutical drugs. When the modified bacteria have produced a desired substance (eg, insulin or enzymes used in food production), that product is separated from the bacteria, purified and processed into its final form. Other micro-organisms such as yeast are also commonly genetically modified for similar purposes.
Did you know?
Genetic modification has a variety of uses - pure science, research, medicine, food production, agricultural innovation.
Plants have been modified for a number of purposes, mostly to make them resistant to pests and diseases, to extend their growing season, or to increase crop yields. Other plants are being modified to increase their nutritional value, to grow in difficult environments or to carry vaccines against diseases. Ornamental plants have been genetically modified to produce new colours or to extend vase life.
Animals have been used mainly for medical research. For example, mice have been genetically modified to help with cancer research. Genetic modification could also potentially be used to improve breeding techniques or to induce cows to produce medical compounds in their milk. Some animals, such as salmon, have been genetically modified to enhance their utility as a farmable food source.
Genetic modification of human cells has the potential for treating diseases. One approach, gene therapy, delivers 'corrected' genes into selected cells in the body to treat diseases caused by an absence of an important gene, such as in cystic fibrosis. In these cases the genetic changes are not passed down to future generations. Research is under way to investigate the potential to modify the DNA in sperm, eggs or embryos to eliminate serious inherited diseases such as Huntington's disease. This area of research is highly controversial because of the safety and ethical issues involved.
Genes work by coding instructions for making proteins and proteins are the chemicals that have a strong influence on biological functions.