In this blog post, we’ll explore CRISPR gene editing technology—a breakthrough in life sciences—and the ethical issues it raises.
People born with genetic diseases eliminated before they’re even born, and others born with predetermined appearances and intelligence. This is the world depicted in the movie *Gattaca*. In the film, couples use advanced life science technology to modify the genetic information of their fertilized eggs as they wish, giving birth to “designer babies.” When the film was released in 1997, many people believed such a world would only be possible in the distant future. However, today, the likelihood that this future will soon become a reality has greatly increased—thanks to “CRISPR gene-editing technology.”
CRISPR is a term originally used to describe a characteristic repetitive nucleotide sequence found in bacteria. Many scientists wondered why bacteria possessed such a unique nucleotide sequence. It wasn’t until 2005 that it was discovered that bacteria possess CRISPR to defend against viral invasions. Whenever a virus invades, the bacterium replicates and stores a portion of that virus’s nucleotide sequence. This stored sequence is then used to recognize and attack the virus should it invade again. The viral genetic material stored by the bacterium is precisely what CRISPR consists of.
So how does CRISPR eliminate viruses? In fact, eliminating viruses requires not only CRISPR but also the help of an enzyme called “Cas9.” Cas9 is an enzyme capable of cutting DNA strands. When a virus re-invades the bacterium, the bacterium uses the pre-stored CRISPR to bind to the complementary base pair in the virus’s genetic material. Cas9 then locates the CRISPR and cuts the viral DNA where the CRISPR is attached. The virus, with its genetic material cut, loses its potency and breaks down, keeping the bacterium safe.
CRISPR gene editing technology was developed by applying this process. For example, if you want to remove the gene responsible for making tomatoes soft, you create a “guide RNA” by replicating the nucleotide sequences complementary to the sequences immediately before and after that gene. Next, the Cas9 enzyme is attached to the guide RNA, and the complex is inserted into the nucleus where the tomato’s genes are located. Just like in bacterial CRISPR, the guide RNA binds to the regions flanking the gene responsible for softening the tomato, and the Cas9 enzyme cuts it. Through this process, tomatoes with the softening gene removed will not soften over time.
Existing gene-editing tools, such as zinc finger nucleases (ZFNs) and TALENs, were developed by mimicking restriction enzymes found in animals or plants, making their production processes complex and costly. However, CRISPR gene scissors utilize bacterial RNA, allowing for much simpler and more affordable production. Furthermore, since RNA can bind complementarily to a much larger number of base pairs than restriction enzymes, CRISPR gene scissors allow for more precise work than before. This has made it possible to produce GMO foods and treat genetic incurable diseases—achievements that were previously unattainable.
However, alongside technological advancements, ethical issues are of critical importance. Genetic engineering has long been a source of controversy due to concerns that it may infringe upon the dignity of life. Moreover, with the advent of CRISPR gene editing and the rapid advancement of genetic technology, we must take a step back and consider both technology and ethics in a balanced manner. Science is like a double-edged sword. I hope that by harmonizing technological progress with ethical considerations, CRISPR gene editing will contribute positively to society.
