By Matt McIntosh
How gene editing works, and why it’s so revolutionary.
Gene editing is a big deal in more ways than one. But while the technology has already had a significant impact in our food and healthcare system, understanding how gene editing differs from other tools in genetic science is, for many, less clear.
Let’s run through it – what gene editing is, what it isn’t, and how it works.
A more precise method
The traditional way of making new and improved varieties of plants and animals is through breeding – that is, crossing two different types of the same or related organisms to try and emphasize desirable traits.
In plants, this could mean selecting for higher food production capability, drought tolerance, resistance to pests and disease, and many other factors. It’s much the same for animals. Livestock, for example, can be selectively bred for lower disease risk, more meat or dairy production, desirable physical characteristics, and so on. Most plants, animals – and even pets – which are familiar to us today are a result of this human-directed evolutionary process.
The trouble with traditional breeding? It can be a slow process, and results are not guaranteed.
New organisms developed through traditional breeding methods are a result of combining two full sets of DNA, meaning it’s possible to transfer both desirable and undesirable traits. Combining two plants might, for example, successfully create a variety which produces more food, but that also turns out to be more susceptible to drought. Breeding two different dairy goats could result in a goat that produces more milk, but which is also more susceptible to specific diseases.
Breeders used gene editing to increase disease tolerance in the Cavendish banana. This same result could have happened by crossing commercial bananas with a wild banana variety with the sought-after disease tolerance, but it would have taken much longer and likely brought some of the unwanted traits from the wild banana as well (such as a smaller size or big seeds).
These are simplified examples, but they illustrate how challenging (and time-consuming) plant and animal science can be. Indeed, it can take years or decades for plant and animal breeders to achieve their goals through traditional breeding techniques.
Gene editing can – and is – solving many of these challenges.
How it works
Different genes within a DNA sequence are responsible for different traits. Gene editing refers to our ability to precisely target and change specific parts of an organism’s DNA sequence by turning the gene off, removing, adding, or replicating it. Doing so means scientists can achieve the desired change in the organism right away, using the genes already present in the organism’s DNA sequence – and minimizing the risks associated with traditional breeding methods.
One of the revolutionary technologies allowing scientists to change plant and animal DNA directly is called CRISPR (or clustered regularly interspaced short palindromic repeats, if written in full). CRISPR is comprised of an enzyme which does the work of changing the targeted gene, as well as a sequence of nucleic acid (called RNA) which guides the enzyme to the target gene. It is the most efficient and precise way we have for making changes to DNA.
It’s important to note here that the ability to use gene editing also required knowledge of the specific edits that were needed. Extensive research is conducted in advance of gene editing a plant to confirm what a gene does and which genes should be edited to get the desired result. These capabilities have been significantly enhanced in the last few decades as a result of important breakthroughs in genome sequencing.
It’s tough to overstate the significance of CRISPR as a technology. Indeed, it has already had an enormous impact in everything from food and agriculture to industrial materials and health care – that includes many of the vaccines we now have for Covid-19. The development of CRISPR has been so revolutionary, its creators were awarded a Nobel Peace Prize in 2020.
Gene editing and GMOs – related, but different
If this description of gene editing sounds like we’re discussing GMOs, you’re right – sort of.
GMO (genetically engineered organism) is the term commonly applied to plants and animals created through “transgenic” engineering. That is, introducing one or more genes into an organism from another organism, whether a related or unrelated species. This technology has been in use for many decades, and has been employed by both public researchers and private companies to create many crop varieties which have benefited farmers, consumers, and the environment.
Gene editing is another form of genetic engineering. While it can be used to introduce new genes and create GMOs, it is focused on making precise edits that already exist or could have arisen through conventional plant breeding. The distinction can sometimes be lost, in part because the way terms like GMO and genetic engineering are used by the general public is often different from their overarching scientific meaning.
There are regulatory differences, too. Products developed using the transgenic method must meet additional safety verification requirements set by the federal government. For products developed through gene editing, regulatory policies are still under development, but many countries have developed separate processes for products of gene editing that are similar/indistinguishable from products of conventional plant breeding and don’t require lengthy pre-market assessments.