Clustered regularly interspaced short palindromic repeats, or CRISPR, are used by microbes to defend against invaders (Prillaman, 2024). In 2005, researchers discovered a new function of CRISPR—that of an immune system (Prillaman, 2024). CRISPR creates new RNA which binds to the DNA sequence of a virus and destroys it, eliminating the threat (Prillaman, 2024). Already, a child diagnosed with a rare genetic disorder has been cured with CRISPR, and they are now thriving thanks to the efforts of the researchers (Musunuru et al., 2025). Later on, CRISPR was adapted by scientists to use in the laboratory to help them isolate and alter the DNA to be used on living organisms (Smith, 2025). 

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Originally, scientists tried using human T cells to control and fight diseases, but they found that the complex nature of the cells can cause undesired reactions when inserted back into the human body (Prillaman, 2024). Scientists were also limited to gene editing a singular protein, which, according to Stanford bioengineer Stanely Qi, often led to unpredicted results (Prillaman, 2024). In the long run, it was not a practical tool to use, especially on a large scale (Prillaman, 2024). This is where CRISPR proves to be a better and safer method; researchers control CRISPR entirely, allowing them to safely isolate their desired gene, although they control side effects from selected gene editing (Prillaman, 2024). Additionally, CRISPR targets genes using RNA instead of the protein, which allows scientists to truncate the protein creation process at the root, instead of eliminating each one after it has already been created (Prillaman, 2024).

 

In Hong Kong in 2018, during an international summit discussing genome editing,  Chinese scientist He Jiankui declared that he successfully modified the genomes of twin girls using CRISPR (Cohen 2019). His intention was to create an innate resistance to the human immunodeficiency virus (HIV), which could also be passed onto the offspring (Normile, 2018). He selected the C-C motif chemokine receptor 5 gene (CCR5), which had previously proved to have an important role in HIV infection (Ma et al., 2019). To add on, He targeted this specific gene because around one percent of northern Europeans—called CCR5Δ32 homozygotes—are born naturally missing the gene, and they appear to be more resistant to HIV (Cohen 2019). Therefore, He and his team decided to design CRISPR to cut and add bases CCR5 to incur natural deletion and nonfunctionality of the protein (Cohen 2019). However, some scientists point out that if the gene-editing done on the embryos were past the once-cell stage, it could result in a genetic mosaic where some normal cells still have CCR5, rendering the patient still vulnerable to HIV (Cohen 2019). 

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Some important concerns were raised in response to He’s declaration, including both ethical and scientific issues. The side effects of He’s gene editing are still unclear, and it may result in unexpected diseases and side effects in the future (Ma et al., 2019). In a previous study, scientists found that CCR5 deletion resulted in lupus nephritis susceptibility, increasing an individual’s likelihood to develop kidney damage and inflammation (Ma et al., 2019). According to Anthony Fauci, an HIV researcher in the U.S. National Institute of Allergy and Infectious Diseases in Maryland, gene editing remains “experimental” and “associated with off-target mutations, capable of causing genetic problems early and later in life, including the development of cancer” (Normile, 2018). Furthermore, researchers found that CCR5Δ32 homozygous humans are more susceptible to the West Nile virus, which causes them to be more vulnerable to severe encephalitis and even death (Cohen 2019). Overall, according to neurobiologist Alcino Silva, it is still far too early to apply CRISPR to human experiments, as scientists do not know enough about it yet, and therefore the consequences can be disastrous (Cohen 2019).

 

Ethical considerations are similarly crucial to consider. The Chinese Society for Cell Biology stated that He’s experiment was a “serious violation of the Chinese government’s laws and regulations and the consensus of the Chinese scientific community” (Normile, 2018). Not only that, He’s university issued a statement that they have started looking deeper into his methods because it might “seriously violate academic ethics and academic norms” (Normile, 2018). Many countries, including the U.S., have banned the government funding of such genome editing experiments in humans, but this still leaves a lot of loopholes for privately funded research (Ma et al., 2019). Some people are scared that this “designer” baby experiment could even start a new human species, as the gene editing affects not only the initial patient, but all of their descendents (Prillaman, 2024). Bioethicist Sarah Chan claims that He’s experiment threatens to cross the fine line of what is morally justified in science, ultimately destroying its relationship with society (Normile, 2018). Genome modification and CRISPR usage must be strictly monitored in the future, with consent of those involved and regular follow-ups to ensure researchers are not overstepping (Normile, 2018). Despite all this controversy, He proclaims that his “designer” babies are ethical, as they help families avoid risks of hereditary diseases (Normile, 2018). Even with He’s justification, however, there is no denying that CRISPR is still not fully understood and developed, and thus should not be considered in a clinical setting, especially one that involves reproductive purposes (Ma et al., 2019). 

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Ultimately, the use of CRISPR in genome editing continues to be a highly controversial topic, as it has yielded positive effects and potential, but still holds the possibility of negative ones. As CRISPR becomes more refined, scientists look forward to using it to treat many genetic diseases, and applying it in the genome and ecological engineering field that offers potentially better manufacturing and more sustainable, eco-friendly opportunities, revealing the endless prospects of this new technology. (Prillaman, 2024).

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References 

Cohen, J. (2019, August 1). Did CRISPR help—or harm—the first-ever gene-edited babies? Science.org. Retrieved October 8, 2025, from 

https://www.science.org/content/article/did-crispr-help-or-harm-first-ever-gene-edited-ba bies 

Ma, Y., Zhang, L., & Qin, C. (2019). The first genetically gene-edited babies: It's "irresponsible and too early". Animal models and experimental medicine, 2(1), 1–4. https://doi.org/10.1002/ame2.12052 

Musunuru et al, “Patient-Specific In Vivo Gene Editing to Treat a Rare Genetic Disease.” N Engl J Med. Online May 15, 2025. DOI: 10.1056/NEJMoa2504747. 

Normile, D. (2018, November 26). CRISPR bombshell: Chinese researcher claims to have created gene-edited twins. Science.org. Retrieved October 8, 2025, from 

https://www.science.org/content/article/crispr-bombshell-chinese-researcher-claims-have created-gene-edited-twins 

Prillaman, M. (2024, June 10). What is CRISPR? A bioengineer explains. Stanford Report. Retrieved October 8, 2025, from 

https://news.stanford.edu/stories/2024/06/stanford-explainer-crispr-gene-editing-and-beyond 

Smith, M. (2025, October 8). CRISPR. National Human Genome Research Institute. Retrieved October 8, 2025, from https://www.genome.gov/genetics-glossary/CRISPR