How GMOs can help Solve Climate Change

11 minute read

Updated on: 06 Aug 2020

Can we alter an organism’s DNA without selective breeding?

Yes!

Rapid advances in our understanding of DNA have enabled scientists to transfer genes directly between different species, and even edit the genome itself!

Organisms produced in this way are often called genetically modified organisms, or GMOs. However, this name is a bit misleading. As we learnt in the previous chapter, humans have been genetically modifying crops and livestock for thousands of years. Therefore, we will be using a more precise term to describe the direct modification of an organism’s DNA: genetic engineering (GE).

Image of Genetic engineering

Genetic engineering

Genetically engineered organisms (GEOs) get a lot of bad press, but they’re actually really important, not just for sustainable agriculture but also for producing medicines and treating genetic diseases.

In this chapter, we’ll look at how GEOs can be useful in agriculture and consider what the risks are.

How do scientists make GEOs?

The first GEOs were produced by transferring genes from one organism to another. How does this work?

  1. Identify the gene that controls a desired trait in a particular organism e.g. disease resistance
  2. Copy that gene
  3. Insert the gene into the genome of another organism
Image of Transferring DNA between organisms

Transferring DNA between organisms

By copying and pasting genes from one plant to another, scientists have created crops which are higher yielding, more nutritious, and in many cases better for the environment than conventional crops.

Let’s look at some examples:

  • Resistance to pests and disease decreases the need for pesticides
  • Increased resilience against heat, drought, and salty soils improves yields in climates that are challenging for crop growth
  • Introducing genes for the production of essential nutrients into staple foods can reduce malnutrition and improve human health
  • Genes that increase shelf life reduce food waste

Increasing yields not only improves food security, but also improves farmers’ incomes. Clearly, there are many benefits to genetic modification. So why do many people still object to it?

What are the risks of genetic engineering?

While GEOs provide many environmental benefits, we must also consider their potential risks. Crops and livestock with resistance to insects and diseases could encourage pests to evolve around these defences, making them harder to control.

If the inserted gene makes the GEO better adapted to its environment, it could compete with wild populations for food and space, reducing biodiversity. Alternatively, the GEO could breed with wild relatives, introducing the transferred gene into wild populations.

Producing GEOs that don’t pass on modified DNA is useful for preventing gene escape. However, it also prevents farmers from re-planting seeds gathered from their crops to harvest the following year. This forces farmers to rely on commercial seed suppliers, giving these companies a lot of control over the farmer’s access to GE technologies. We will discuss why this is an issue in the Open Problems chapter.

Image of People have different opinions on GEOs

People have different opinions on GEOs

Perhaps the biggest public concern over GEOs is the potential risk of GE food on human health. Is this justified?

When genes are transferred from one organism to another using conventional GE techniques, they can be inserted anywhere in the genome. This can have negative side effects, such as the production of toxins and accidental disruption of other genes. Transferred genes may also trigger reactions in people who are allergic to the organism from which the gene was copied.

Therefore, while scientists largely agree that GE food is just as safe as non-GE food, it is important that GEOs are rigorously tested before they are sold.

Many of these concerns relate to the transfer of genes between different organisms. What if we could introduce desired traits by editing the DNA directly?

What is genome editing?

While traditional methods of genetic engineering involve the transfer of DNA from one organism to another, recent discoveries in molecular biology have made it possible to edit the genome of an organism directly.

The most efficient tool for genome editing we have today is the CRISPR-Cas system, often just called CRISPR.

CRISPR is a natural system used by bacteria to defend themselves against viruses. How does it work?

The name CRISPR actually refers to a short sequence of DNA. In nature, the CRISPR sequence matches the DNA of a virus that previously infected the cell. If the virus tries to re-invade, these CRISPR sequences can be used by CRISPR-associated (Cas) proteins that act like sniffer dogs to find the matching DNA. When Cas proteins find the virus, they make a cut in the virus’s DNA and deactivate the intruder.

Image of CRISPR in Bacteria

CRISPR in Bacteria

So how is this used in genome editing?

Using these principles, Cas proteins can be trained to locate and cut any gene in an organism’s genome, provided we know its DNA sequence. With the help of the cell’s own repair systems (that fix any errors or breaks in the cell’s DNA), new genes can be inserted where the DNA is cut.

Image of CRISPR/Cas Gene Editing

CRISPR/Cas Gene Editing

But CRISPR is not only used to transfer genes from one organism to another. It can also be used to edit the genome directly.

If no new genes are introduced, the cell will still repair the snipped DNA. However, these repair mechanisms are not always accurate, and can disrupt the gene by adding or deleting part of its DNA. This might sound like a bad thing, but it can be really useful if the disrupted gene gives the organism a beneficial trait, such as disease resistance.

Furthermore, by introducing these new versions of genes into plant genomes, CRISPR can increase the genetic diversity of a species. This in turn provides more genetic variation for traditional selective breeders to work with.

Image of Alternative products of CRISPR

Alternative products of CRISPR

Since its discovery, there has been an explosion in research to develop new ways to use CRISPR technology. For example, by modifying the Cas protein, scientists are now able to precisely edit each of the individual letters in a gene’s sequence!

CRISPR is much more precise and less expensive than traditional methods of genetic engineering. In fact, CRISPR can be used to produce genome-edited organisms that have no “foreign” DNA at all. This means that the edited genes are technically no different to those produced through the random changes that occur naturally in an organism’s DNA over time!

Conclusions

Farmers have been genetically modifying crops for thousands of years: genetic engineering just allows these changes to occur faster and more precisely. GE crops have the potential to make agriculture more sustainable, while improving the income of farmers and the nutritional content of foods.

However, many people are still uncomfortable with the idea of GE food. This is largely down to a lack of clear communication between scientists and the general public.

Advances in genome editing have made genetic engineering safer and more precise than ever before, and it is now possible to genetically engineer products with no “foreign” DNA at all. For this reason, many argue that “food regulations”, the rules dictating whether a product can be sold as food, should be based on the safety of the food itself, rather than the process by which it was produced. Indeed, this is already the case in the USA and Canada.

Even so, assessment of the potential environmental and health risks of all new products will still be essential, as well as regulations to ensure these tools are only used for ethical purposes.

By educating people about the benefits of GEO technologies and clearly addressing their concerns, GE food may become more widely accepted.

So far we’ve looked at the problems of crop farming, and how genetic engineering, agroecology, and precision farming could be used to solve them. But what about farming animals? We’ll look at that in the next chapter.

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