What if you could change how organisms express themselves, giving them completely new characteristics? Or perhaps fight off diseases that have long plagued humans?
That is precisely what genetic engineering does; scientists use a variety of methods to modify the tiny instructions that give a living organism its characteristics and functions. For billions of years, DNA, the code for organisms, could only be slowly modified over millions of years, giving organisms specific traits through evolution and natural selection. However, scientists are now able to precisely rewrite an organism’s genetic code, changing its features much faster than evolution would. Genetic engineering isn’t just a theory; it’s happening right now. It’s how scientists are curing diseases, fighting climate change, and making agriculture more efficient.
Genetic engineering may involve deleting a region of DNA, or adding a new segment of DNA [1] to the organism’s genetic code, thereby changing its features. One method that scientists use to accomplish these alterations of DNA is through CRISPR (also known as Clustered Regularly Interspaced Short Palindromic Repeats). Interestingly, CRISPR isn’t a tool that scientists invented from scratch; it’s actually a natural defense method found in bacteria that help them fight off viruses. When a bacterium is attacked by a virus, it stores a part of the virus’ DNA in its own genome. That way, if the bacterium is infected by the same virus again, it can recognize and easily eliminate the threat, like how vaccines work for our own bodies [2].
Looking further into the CRISPR system, scientists discovered a DNA-cutting protein called Cas9. They then realized that they could edit the genomes of plant and animal cells using “guide RNA,” essentially a GPS for Cas9. The guide RNA tells the Cas9 protein where to go, cutting out specific regions of DNA under a scientist’s guidance [3]. This way, harmful molecules can be removed from organisms, allowing for the organism to heal themselves. Alternatively, scientists may even introduce different DNA to replace the cut-out DNA region.
In addition to deleting unwanted DNA, scientists can also use recombinant DNA to “grow” and introduce new DNA to an organism. In this process, DNA of interest is taken and combined (or spliced) into a plasmid, a type of circular DNA found in bacterial cells. Restriction enzymes cleave DNA at specific locations, while DNA ligase acts as a glue and joins the new DNA to the plasmid. In the next step, the plasmid is introduced into bacterial cells. This “recombinant” DNA is then replicated over and over again as the bacterium reproduces, copying the engineered DNA as well as itself [4] [5]. With a whole batch of DNA-containing bacteria, scientists then select and screen for the transformed cells.
But how do scientists actually deliver the DNA into other organisms? This is where viruses come in. Ordinarily, contracting a virus sounds like a bad thing. However, scientists actually genetically modify viruses to contain helpful, therapeutic genes, leveraging the viruses’ natural ability to infect cells. One of the most effective gene delivery vehicles, modified viruses, can efficiently target genes to enhance immune response or correct genetic defects [6].
With precise and effective tools to edit an organism’s characteristics, scientists have already used genetic engineering to innovate in many different fields. For example, in cancer research, researchers use CRISPR to change genes linked to cancer, then closely track the individual cells that form [2]. CRISPR has also been applied in the agriculture industry, modifying crops to have better quality, disease-resistance, and even yield [2]. Recombinant DNA has been used in the healthcare industry, producing recombinant proteins for therapeutic purposes. Notably, recombinant technology was used to create human growth hormones to treat growth hormone deficiency in children, as well as produce insulin to treat diabetes without the use of cattle and pigs—which could cause allergic reactions [5].
While the benefits of genetic engineering are apparent and already applied in several different fields, there are also risks that need to be considered. The most likely problem is unexpected allergenicity. If allergenic proteins are transferred between foods through recombinant technology, it can cause unanticipated allergic reactions in people who ate it. Another possible problem is the activation of unknown, nonfunctional genes that are harmful toward humans and animals. By randomly inserting transgenes into an organism, scientists may inadvertently activate previously inactive genes in the target genome, possibly producing harmful compounds [7].
Apart from damage to humans, genetic engineering may also hurt the environment. If environmentally advantageous genes are transferred to crops, then those crops may become weeds. For example, tolerance of high-salt environments is a desirable trait for many crops. However, the addition of advantageous genes may allow the crop-weed hybrids to displace other naturally occurring salt-tolerant species. Another risk could be the adaptation of pests as the pests grow more used to a resistant gene. Historically, the use of a widespread resistant gene in domesticated species has led to adaptation in the pest population, as the pests grow more used to the resistant gene. Recombinant technology may accelerate this, as the resistant gene will most likely be used over large areas due to the immediate economic benefits that a grower or producer can obtain [7].
While genetic engineering is a route to quick genome editing in organisms and therefore its characteristics, it still is a very new technology, whose effects have not been thoroughly studied yet. The benefits are clear, but scientists should explore the possible risks of genetic engineering before using it extensively.