Genes contain the instructions that determine many of the characteristics of living organisms and control how their cells function. But can scientists change these instructions?
Could we make bacteria produce useful medicines, develop crops that survive drought, make food more nutritious, protect plants from pests or even correct genes that cause disease?
Yes. Scientists can do this using genetic modification and gene editing.
Although the two technologies are related, they are not exactly the same. Genetic modification generally involves introducing new genetic material into an organism to give it a desired characteristic. Gene editing allows scientists to make a more targeted change to DNA, such as removing, switching off or altering a particular gene.
Think of DNA as an instruction book. Genetic modification is like adding a new instruction, while gene editing is like finding a particular instruction and correcting it.
Medicine made by microorganisms
One of the best-known examples of genetic modification is human insulin.
People with diabetes may need insulin to control their blood glucose levels. Before modern biotechnology, insulin was obtained from the pancreases of animals such as pigs and cattle.
Scientists developed a way to make microorganisms produce human insulin. They introduced the human gene responsible for insulin production into bacteria or yeast. The modified microorganisms then used this genetic information to produce insulin.
The insulin is collected and purified before being used as medicine.
In this way, microorganisms become tiny biological factories producing an important medicine.
Cheese without the calf
Genetic modification has also changed the way we make cheese.
Cheese-making requires an enzyme called chymosin, which causes milk to form curds. Traditionally, chymosin was obtained from the stomachs of young calves.
Scientists found a different solution. They introduced the genetic instructions for producing chymosin into microorganisms. These microorganisms can then produce the enzyme, which is collected and purified for use in cheese-making.
This allows large quantities of chymosin to be produced without obtaining it directly from calves.
So, biotechnology can be found in something as familiar as the cheese on a pizza.
Crops with useful characteristics
Genetic modification can also give crops characteristics that benefit farmers and consumers.
Insect-resistant brinjal, for example, has been developed to protect plants from certain insect pests by inserting bacterial gene. This can reduce crop damage and may reduce the need for some insecticide applications.
Virus-resistant papaya was developed to protect papaya plants against papaya ringspot virus, which can severely damage crops.
Another example is the non-browning apple. When an apple is cut, enzymes cause the flesh to turn brown. Scientists have developed varieties in which the activity of these enzymes is reduced. The cut apple therefore stays attractive for longer, which can help reduce food waste.
Scientists are also exploring crops that can tolerate drought, heat, salinity and other environmental stresses.
How is genetic modification done?
So, how does a scientist actually add a new gene to an organism?
First, scientists identify a gene responsible for the desired characteristic. For example, they may identify a gene that can provide resistance to a particular insect pest.
The selected DNA is then introduced into cells of the organism. In plants, one commonly used method involves Agrobacterium, a naturally occurring soil bacterium that can transfer DNA into plant cells. Other methods can also be used.
Scientists then identify the cells that have received the desired genetic material. In plants, these cells can be grown using tissue culture to produce a complete plant.
The new plant is then tested to confirm that the introduced gene is present and that the desired characteristic has been produced.
In simple terms:
Identify the useful gene → introduce the DNA → select modified cells → grow the organism → test the new characteristic.
Gene editing: making a targeted change
Gene editing takes a different approach. Instead of necessarily adding a new gene, scientists can make a targeted change to existing DNA.
One of the best-known gene-editing technologies is CRISPR-Cas9.
Imagine DNA as a huge instruction book. CRISPR can be designed to locate a particular sequence in that book. A guide molecule directs the Cas9 enzyme to the selected DNA sequence, where it makes a cut. Cas9 enzyme acts like a scissors here.
The cell then attempts to repair the DNA. Scientists can use this natural repair process to create a desired change.
For example, a gene can be disrupted so that it no longer works. In other cases, scientists can provide a DNA template to help the cell make a specific correction.
The simplified process is:
Identify the target → design the guide → direct the editing machinery to the DNA → make the change → allow the cell to repair itself → check the result.
Scientists then examine the cells carefully to confirm that the intended change occurred and to look for unintended changes.
Can gene editing treat disease?
One of the most exciting applications of gene editing is medicine.
Some diseases are caused by changes in particular genes. If scientists can correct or alter these genes, they may be able to address the underlying cause of a disease.
Gene-editing treatments have already reached patients for certain genetic disorders. Sickle cell disease is one important example. Some treatments use gene editing on a patient’s blood-forming stem cells to alter how they produce haemoglobin, helping to reduce the effects of the disease.
Researchers are also studying gene editing for other inherited diseases and cancer.
However, gene editing is not a universal cure for cancer. Cancer can involve many genes and complex interactions between cells and the environment. Researchers must also carefully assess the safety of gene-editing treatments.
Gene editing in food and farming
Gene editing is also being investigated for agriculture.
Scientists can target genes associated with characteristics such as growth, disease resistance, nutritional content and tolerance to environmental stresses.
In fish farming, Japanese scientists have developed fast growing sea bream. In crops, gene editing is being explored to develop plants that are more resistant to disease or better able to cope with difficult growing conditions.
Such technologies could potentially help farmers produce more food while using fewer resources. However, scientists also need to consider food safety, animal welfare and environmental effects.
Microbes that help clean pollution
Genetic modification can even be used to explore ways of cleaning polluted environments.
Some bacteria naturally have the ability to break down hydrocarbons and other pollutants. Scientists can study the genes responsible for these abilities and investigate whether microorganisms can be modified to break down particular substances more effectively.
One bacterium that has been studied for this purpose is Pseudomonas putida, which can break down certain hydrocarbons.
The idea is intriguing: microorganisms could potentially become part of the toolkit used to clean contaminated environments.
However, genetically modified organisms released into the environment must be carefully assessed because scientists need to understand their possible effects on ecosystems. These technologies must be used responsibly. Safety, environmental impact, animal welfare, ethics and regulation all need to be considered.
