PDF Summary:The Code Breaker, by Walter Isaacson

How might the gene editing technology called CRISPR transform humanity? In his 2021 book The Code Breaker, journalist, historian, and award-winning biographer Walter Isaacson discusses the advent and future of this groundbreaking scientific tool. He traces its development (focusing on Nobel Prize winner Jennifer Doudna) and explores its significance as a victory for women in science. He also argues that CRISPR has the potential to change life as we know it and explains how, in some ways, it already has.

This guide focuses on four ideas: the biological feature known as CRISPR, Doudna and the other scientists who developed the CRISPR gene editing technology, the moral quandaries CRISPR technology presents, and some of CRISPR’s realized and potential real-world applications. In our commentary, we’ll explain updates on CRISPR science since the book’s publication, explore key scientists’ careers in greater detail, and discuss various philosophical perspectives on CRISPR-related moral issues.

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According to Isaacson, the race to optimize CRISPR gene editing technology for human cells was close. Zhang made modifications to the original version of sgRNA that Doudna and Charpentier developed. His paper was published the same day as another scientist’s paper, and the other scientist’s modifications to sgRNA proved more suitable for human DNA editing than Zhang’s. Later the same month, Doudna published her own paper, which demonstrated another way to apply CRISPR to human cells. Two other scientists published papers on the same topic that year. Since multiple scientists made significant contributions to the application of CRISPR gene editing technology in human cells, it was difficult to say who invented the process.

Comparing Doudna’s and Zhang’s Contributions to CRISPR Science

Isaacson explains that when Doudna and Charpentier first invented the CRISPR tool, it wasn’t clear whether it would work in complex cells like human cells. But in the war for patent rights (which we’ll cover soon), Doudna’s lawyers argued just the opposite: The average expert could have reasonably expected to succeed in using CRISPR technology in eukaryotic (complex) cells since several scientists achieved that feat quickly after CRISPR’s development. However, since Doudna and Charpentier explicitly stated that they didn’t expect to accomplish this easily, it’s significant that Zhang was the first to actually do so, even though he didn’t completely understand the roles of Cas9 and tracrRNA in the process.

However, neither Zhang nor Doudna—nor any other scientist—safely optimized CRISPR for use in human cells (although scientists continue to research solutions to this problem). As we mentioned earlier, many different gRNA tools have been invented to suit various gene editing projects’ particular needs (including sgRNA optimized for use in human cells), and some experts suggest that dual-guide and single-guide RNA work equally well. This fact may support Zhang’s argument that Doudna and Charpentier’s sgRNA isn’t integral to CRISPR gene editing technology, undermining the pair’s case for patent rights.

The War for Patent Rights and Recognition

Isaacson explains that both academia and the biotechnology industry are extremely competitive. In academia, being the first to make a discovery leads to greater prestige and career success. In the biotechnology industry, being first enables you to develop patents. (Shortform note: Patents are important to inventors because they prevent others from taking credit for or profiting from your invention, which enables you to make more money.)

The competitive nature of scientific research—and the ambiguity surrounding who truly invented the process for human gene editing—led Doudna, Charpentier, and Zhang to become embroiled in a war for patent rights and recognition. Let’s explore how that played out.

In 2013, Doudna, Zhang, and other scientists established a CRISPR-focused medical research company together called Editas Medicine. However, Doudna left the company a few months later due to a conflict: Doudna and Charpentier had applied for a patent together, as had Zhang and his team. Zhang paid to accelerate the application process, so he was granted the patent for CRISPR first. Isaacson says that Doudna felt this was unfair: She believed she and Charpentier were the first to develop the technology, and she thought Zhang’s actions were underhanded and proved him untrustworthy. She left Editas Medicine to join Intellia, an offshoot of a biotechnology company she’d built earlier in her career (Caribou Biosciences).

Meanwhile, conflict was also brewing between Doudna and Charpentier: Charpentier viewed herself as the primary researcher who discovered CRISPR technology, while Doudna felt it was a joint project for which she was entitled equal recognition. Due to this conflict, Charpentier formed her own biotechnology company instead of joining Doudna (or Zhang). (Shortform note: It’s unclear whether Doudna and Charpentier have bridged the gap that grew between them. But as of 2023, they continue to have collegiate links—Doudna’s Innovative Genomic Institute celebrated the many strides made by Charpentier’s company, CRISPR Therapeutics, toward further applications of CRISPR technology.)

Nevertheless, Doudna and Charpentier were jointly awarded several prizes for their work on CRISPR. Isaacson explains that these prizes affirmed two things: Doudna and Charpentier had made relatively equal contributions, and despite Zhang’s patent approval, they were the first to discover the technology. These affirmations were echoed by the greater scientific community when one of Zhang’s associates published an article lauding Zhang for his contributions to the discovery. Critics of the article argued that the article’s writer ignored Doudna’s contributions because he was sexist, which led to a Twitter firestorm.

(Shortform note: Twitter has long served as a digital hub for professionals in academia (but this has changed somewhat since Elon Musk took ownership of the platform). So-called Academic Twitter is good for building rapport among colleagues regardless of physical distance, but it’s also been home to several career-stopping academic scandals over the years. In addition to the Twitter firestorm over who deserved credit for CRISPR’s development, Doudna and Zhang’s respective companies waged a silent online battle over their claims to CRISPR-related Twitter handles).

Isaacson explains that since their application was still being processed when Zhang’s patent was awarded, Doudna and Charpentier were legally entitled to continue fighting for patent rights. They argued in court that they deserved the patent because they were the first to develop CRISPR gene editing technology and to say that it could be used in human cells. Zhang countered that he deserved the patent because Doudna and Charpentier’s original version of sgRNA didn’t work in humans and his innovation solved that problem. The US Patent Office determined Zhang should have the patent after all, but Doudna and Charpentier won other patent wars abroad, in nations like Mexico, China, New Zealand, and Japan.

The Fallout of the Patent Wars

The patent wars between Zhang and Doudna and Charpentier haven’t been resolved—and at times, they’ve gotten grisly. Doudna’s lawyers accused Zhang of knowingly misrepresenting the truth in his patent applications, citing email admissions from a researcher in his lab as evidence. Zhang and his representatives denied these charges; since he was ultimately awarded a patent, it’s probable that the courts didn’t find substantial enough evidence that he lied. However, the patent war didn’t end there—Doudna continued to file for CRISPR-related patents, which prompted patent authorities to re-investigate the issue. In a 2022 decision, the patent court again upheld Zhang’s original patent grant.

Doudna’s US appeal of Zhang’s patent victory was pending as of July 2023. Other authorities, including Japan’s Patent Office and the National Inventors Hall of Fame, recognize Doudna and Charpentier as the first to invent CRISPR for eukaryotic gene editing.

Some experts believe that Zhang’s victory in the patent wars for CRISPR technology could jam up the deployment of CRISPR therapies with patent infringement lawsuits. However, suing people who use the technology could harm Zhang’s reputation, since Americans are increasingly critical of greedy behavior in the medical technology and pharmaceutical industry. Zhang’s employer, the Broad Institute, committed to sharing access to CRISPR technology with global scientists for therapeutic and agricultural research. And in 2023, Zhang’s company Editas Medicine licensed CRISPR to Vertex Pharmaceuticals for sickle cell disease therapy.

How CRISPR Launched Doudna’s Career

Isaacson explains that despite her loss in the war for US patent rights, Doudna’s career has benefited tremendously from her contributions to CRISPR science and technology. He focuses on two primary benefits: First, Doudna entered the biotechnology industry. As we mentioned earlier, she started her own company (Caribou Biosciences), briefly worked for Editas Medicine with Zhang, and then returned to Caribou by joining its offshoot, Intellia. She then founded a research nonprofit (the Innovative Genomics Institute or IGI) and a company called Mammoth Biosciences, which both played an important role in the fight against Covid-19. (We’ll discuss that in more detail later.)

(Shortform note: Biotechnology is a lucrative industry—made more lucrative by the invention of CRISPR—that spans healthcare, environmental, and industrial research applications. As of 2023, Caribou Biosciences had made major advances toward using CRISPR against blood cancers, Editas Medicine had an ongoing clinical trial for CRISPR-derived sickle cell disease treatment, Intellia had an ongoing clinical trial for CRISPR therapies for ATTR amyloidosis (a rare disease that can result in heart failure), the IGI is researching CRISPR cures for environmental and agricultural issues and world hunger, and Mammoth Biosciences is researching CRISPR’s diagnostic applications, including tools that can detect cancer and viral or bacterial infections.)

Second, Doudna and Charpentier were jointly awarded the Nobel Prize in Chemistry in 2020 for their research on CRISPR. Isaacson explains that their victory was historic for a few reasons. First, it usually takes decades for the Nobel Prize Committee to reward contributions to science. Second, there were only two recipients instead of the usual three—which means the committee decided that Zhang and other competitors were less deserving of credit for CRISPR gene editing technology. Finally, for the first time, all the recipients were women (and only five of nearly 200 previous recipients in history had been women). Doudna and Charpentier agreed that this was a monumental win for women and hoped it would inspire girls to pursue science.

(Shortform note: Experts say that Doudna and Charpentier were awarded the Nobel Prize more quickly than usual because their invention had clear potential to change the world; most discoveries and inventions that are awarded the Nobel Prize aren’t quite so groundbreaking. Experts also believe that women receive fewer Nobel Prizes in science than men because of the unique challenges women face in STEM careers we mentioned earlier—and perhaps also because of implicit bias against women on the part of those responsible for recognizing researchers’ most notable achievements. As for why Zhang wasn’t recognized by the Nobel Prize Committee, the committee's chairman declined to comment.)

Part 3: CRISPR Presents Moral Quandaries

Now that you know what CRISPR is and how it came to be, let’s discuss what its advent means for society. First, we’ll discuss the moral quandaries CRISPR gene editing presents. Then, we’ll explain how scientists and policymakers have addressed them so far.

Germline Editing

Isaacson says that most people think it’s morally OK to edit somatic cells—non-reproductive cells that affect only an existing person’s bodily composition. But people disagree about whether it’s OK to edit germline cells, which include eggs and sperm. When you edit germline cells, you genetically modify potential future offspring, and the changes you make could be inherited by their offspring as well. Isaacson describes a few opinions on each side of the debate.

Some people who are against germline editing argue that it’s wrong because it’s heretical or unnatural—either God or nature (via evolution) designed our genes the way they are for a reason, so humans shouldn’t interfere. Isaacson says this argument may not be logical: If nature or God endowed us with the ability to develop and use CRISPR, then using it can’t be unnatural or heretical. He also notes that genes aren’t distributed fairly—some people suffer more than others for no reason other than the luck of the genetic draw—and we may be morally obligated to even the playing field. However, Isaacson recognizes some existential risks of germline editing: We might develop hubris and become ungrateful for what nature or God gave us.

Some people who are in favor of germline editing argue that we have a moral duty to set our children up for success. Philosopher Julian Savulescu calls this stance “procreative beneficence.” Isaacson says that germline editing would accomplish this goal more efficiently than somatic editing. To illustrate, consider the blood disorder called sickle cell disease: Somatic edits can cure individuals (which we’ll discuss in more detail later), but germline edits could prevent their descendants from developing sickle cell disease in the first place. Theoretically, this would improve human life by leaps and bounds. But there’s also a downside to making germline edits—we might decrease genetic diversity, which is an evolutionary disadvantage.

Weighing Both Sides of the Germline Debate

Isaacson explains that many arguments could be made to justify taking either side of the germline debate. Let’s explore those arguments in more detail now.

Isaacson says some people believe germline gene editing is heretical or unnatural, but that this is illogical because we are endowed with the ability to do so using CRISPR. Another objection to this argument is that while CRISPR germline gene editing would involve purposefully changing our children’s DNA, it’s not unique—we already make mundane choices that have bearing on our children’s genes every day.

For example, we choose mates by subconsciously evaluating their genes, effectively curating the gene pool from which our children’s genes will be derived. We also engage in behaviors with epigenetic effects—effects on how our genes, and sometimes our children’s genes, will be expressed. Smoking, for example, may be associated with inherited epigenetic susceptibility to respiratory problems. Although these cases are obviously different from making direct changes to our children’s DNA, they demonstrate that it’s probably not unnatural or heretical to determine our children’s genes, since we already do so unwittingly every day.

Isaacson suggests we might be morally obliged to correct harmful genetic abnormalities, but this leads to another important question—who decides what qualifies as a problem to be fixed? Some experts are worried that even if that question is decided by the court of public opinion, the answer could result in a phenomenon called “velvet eugenics.” Velvet eugenics occurs when market forces, like the relatively higher cost of raising a child with Down syndrome, influence families to make reproductive choices that prevent the birth of children with genes they determine undesirable (like the mutations that cause Down syndrome). Velvet eugenics differs from traditional eugenics programs, which tend to be state-sponsored, but may have similarly racist and ableist ends.

The fear of velvet eugenics underlies major arguments against Savulesco’s standard of procreative beneficence. Additionally, CRISPR may not even be the best way to accomplish procreative beneficence, since CRISPR germline edits can result in DNA breakage and chromosomal losses, which may create new harmful genetic abnormalities without solving the original problem. But since scientists are continually working toward solutions to safety issues, these concerns may not always stand.

Interventions vs. Enhancements

Isaacson says that scientists aren’t likely to abandon germline editing research, so society must determine under what conditions germline editing should occur. He describes a continuum of conditions that are under heavy debate by experts in the field. Many people believe germline editing is only OK when it serves as a medical intervention (like the sickle cell example we discussed earlier). They don’t believe it’s OK to unnecessarily enhance germline cells (like editing genes to make children conventionally attractive). They view genetic enhancements the way most people view the use of performance enhancement drugs in sports—they give people an unfair advantage and undermine the significance of talent, merit, and success.

(Shortform note: While many people aren’t OK with CRISPR-derived enhancements, some transhumanists (who believe in using technology to enhance humans) argue that germline genetic enhancements are desirable because it’s easier to design perfected people before birth than it is to alter adults. Regardless of your stance on enhancements, you might find CRISPR-derived medical interventions objectionable for various reasons—for example, many CRISPR treatments are tested on animals before they’re used in human trials, and the animals involved may be harmed as a result of these experiments. And in the same way some drug treatments can cause unwanted side effects, some research suggests that CRISPR gene editing poses a non-negligible threat of causing cancer.)

But Isaacson explains that the boundary between interventions and enhancements is sometimes unclear—for example, acne is both a medical and cosmetic issue. This issue becomes even murkier when we consider that certain genes often have disadvantages and advantages. For example, inheritable mental illnesses are associated with higher creativity. If we edited out mental illnesses to reduce suffering, it might have a negative effect on the arts.

(Shortform note: The neurodiversity movement underlines the murkiness of the boundary between medical and non-medical issues—advocates of the movement argue that brain differences like autism and ADHD don’t qualify as medical issues that need to be treated, even though medical authorities historically have viewed them that way. Additionally, some experts might take issue with the link Isaacson draws between mental illness and creativity because the association between the two is poorly understood. While the two traits may not be strongly correlated, the stereotype of the “mad genius” persists and may have negative effects on gifted children’s development.)

The Inequality Issue

Finally, Isaacson says that many people are concerned that the advent of human gene editing technology could exacerbate inequality. Gene editing therapies of all types—somatic and germline, interventions and enhancements—are likely to be extremely costly. Therefore, they’d only be available to wealthy people. In the case of germline edits, the edits would be inheritable, which means wealthy people’s descendants would be genetically advantaged. Over time, this could significantly widen the gap between rich and poor people—wealth and poverty would be inscribed in our genetic makeup, leading to clearly apparent differences in our features and abilities.

(Shortform note: It’s possible that non-human gene editing could exacerbate global inequalities, too. Experts note that CRISPR is transforming the agricultural industry, as scientists use gene editing to produce more nutritious food sources that are less susceptible to blight, other diseases, and drought. This seems like a good thing on its face—but these methods are costly to research, develop, and implement, and they may not be accessible to low-GDP nations. Thus, CRISPR’s use in agriculture may widen the gap between rich and poor people on a global scale, which may in turn be genetically inscribed due to the inheritable epigenetic consequences of poor nutrition. Some experts are therefore calling for the democratization of CRISPR gene editing technology.)

For this reason, writes Isaacson, some detractors argue that gene editing should be strictly regulated (if it’s allowed at all) so that it can only benefit society, not make it worse. On the other hand, some proponents of gene editing believe that free-market capitalism entitles us to make the best choices available to us given our individual means. For those on this side of the debate, individual freedoms outweigh any concern for the potential cumulative effects gene editing may have on society.

(Shortform note: When it comes to public health, barriers to regulation are growing. The US Supreme Court ruled in 1905 that the government has the right to supersede individual freedoms to protect public health when necessary; this ruling served as the basis of government-mandated health regulations like quarantines and mask requirements during the Covid-19 pandemic, and it’s also used to justify the enforcement of vaccination programs. But the growing tension between individual freedom and collective responsibility (exacerbated by the anti-vaccination movement and Covid-related political developments) may result in ideological barriers to CRISPR regulation alongside already-existing bureaucratic barriers to regulation.)

CRISPR-Related Policies

Isaacson explains that when the field of bioengineering gained steam in the 1970s, scientists immediately recognized two threats. First, their research had serious consequences for society. Second, they might face government interference if they didn’t prepare for these consequences responsibly. Therefore, scientists gathered at conferences to create their own policies governing bioengineering research ethics.

(Shortform note: To clarify, gene editing is only one form of bioengineering, a practice that encompasses any method of altering an organism’s DNA (including the creation of genetically modified organisms, or GMOs). It’s possible that bioengineers took their cue to self-regulate because of the 1974 passage of the National Research Act, a law that resulted in tighter regulations of biomedical research in the wake of the Tuskegee scandal. The Tuskegee scandal was a decades-long study in which scientists infected Black American participants with syphilis without their consent and failed to treat them after a treatment was discovered. Research ethics came under broader scrutiny following the exposure of this study.)

After Doudna invented CRISPR gene editing technology, she had a nightmare that Adolf Hitler wanted to use it for nefarious purposes. Isaacson says that this dream, along with other fears about the potential consequences of her invention, led her to revive the tradition of science policymaking. She helped organize a 2015 conference where, after much debate, researchers concluded that germline gene editing research should be paused until scientists knew more about the risks it posed and could come up with safe, ethical research guidelines. However, germline gene editing research later resumed—we’ll discuss why in the next section.

(Shortform note: It’s not uncommon for scientists who make major technological advancements to fear the potential outcomes of their research—for example, J. Robert Oppenheimer expressed anxiety and remorse after he helped develop the atomic bomb, and Mary Shelley famously explored the theme of a scientist’s regret in her novel Frankenstein. Doudna took pains to ensure that her invention wouldn’t be used nefariously—and in 2023, the summit she organized reconvened to update their guidelines. They established that it’s okay to do germline gene editing research, but it’s not safe to do germline experiments that will lead to the birth of gene-edited humans.)

Part 4: CRISPR Applications

Regardless of the as-yet-unresolved moral quandaries that CRISPR presents, research involving CRISPR marches on full steam ahead. In this section, we’ll discuss CRISPR’s many applications—some that have already been realized and some that are yet to come.

Realized Applications of CRISPR

Isaacson describes many realized applications of CRISPR, but we’ll focus on three of the most momentous ones here.

First, in 2019, a Chinese scientist named He Jiankui created the first designer babies (modified humans created via germline gene editing). When the three babies were embryos, he edited a gene they had called CCR5, which makes you susceptible to HIV infection (but also protects you from West Nile Virus). The experiment was controversial because he blatantly disregarded the agreement science policymakers had made to pause germline editing. He faced international criticism and was convicted of criminal charges in China. His experiment led Doudna and other scientists to make a statement denouncing his actions and laying out guidelines for safer future experimentation with germline editing.

Second, CRISPR has been applied as a medical intervention in the form of somatic sickle cell gene therapies. This process involves taking stem cells from a sickle cell patient, editing the DNA in those cells to promote the production of healthy blood cells, and reinjecting the edited cells into the patient. Isaacson says that in 2020, the first patient to receive this treatment was cured of sickle cell disease. The treatment is expensive, and scientists believe germline sickle cell therapy could be more cost effective. However, extensive germline sickle cell therapy could be problematic: Most people with sickle cell disease live in parts of Africa where malaria is endemic, and the sickle cell gene protects you from malaria.

(Shortform note: As of 2023, US authorities had officially approved two CRISPR-derived somatic gene therapies for sickle cell disease, and there were over 200 patients receiving somatic gene therapies using CRISPR. However, these therapies remain expensive; the sickle cell therapy is estimated to cost $2 million per person. In case concerns about the loss of protection against malaria following sickle cell gene therapy become relevant, Doudna notes that CRISPR could be used to eliminate mosquitoes (the insects that carry malaria). However, this could also have profoundly negative ecological effects.)

Finally, at the biotechnology organizations they founded, Doudna and Zhang spearheaded projects aimed at combating the Covid-19 pandemic. Isaacson says that bureaucratic obstacles prevented the US government from addressing the need for diagnostic tools quickly enough, so private scientists took the lead. Doudna and Zhang adapted diagnostic tools they’d created previously (to test for viruses like Zika and HPV) to diagnose Covid-19. They released simple, disposable, at-home tests for public use in April 2020 and freely shared their methods online so that anyone could use or enhance the technology. Doudna’s colleagues also invented a CRISPR-based vaccination method that may be adapted for use in future viral outbreaks.

(Shortform note: Doudna’s team at the IGI has continued its research on CRISPR-based Covid-19 tests, as has Zhang’s company. In addition to Doudna’s CRISPR-based vaccine, other scientists have used CRISPR to develop promising preventatives and treatments for the Covid-19 virus. Isaacson explains that Doudna’s CRISPR-based vaccine didn’t help much with the Covid-19 pandemic but has potential—the vaccines that did help were mRNA vaccines, and mRNA vaccine technology could be combined with CRISPR technology in the future to deliver gene therapies.)

An Update on He Jiankui and His Designer Babies

Research suggests that editing the CCR5 gene (the gene He Jiankui targeted in his designer babies) results in improved mental function. It’s possible that He Jiankui was aiming for this enhancement instead of the medical benefits he claimed as his motivation, since his experiment was neither medically necessary nor successful at protecting the babies from HIV and may have harmed their immune systems, endangering the babies’ overall health.

He Jiankui served a three-year prison sentence before resuming his work on genetic science, which some experts note may lead to further experimentation with germline gene editing. As for the designer babies He Jiankui created, the scientist claims that they’re happy and healthy. However, since their identities are protected, nobody else has been able to verify this, and Chinese scientists believe that they could suffer from serious genetic conditions.

Potential Applications of CRISPR

As we’ve mentioned, Isaacson explains that many of CRISPR’s realized applications will likely be enhanced and reused in the future (for example, CRISPR-derived tests and vaccines for Covid could be used to combat other viruses). He also notes that gene therapy trials for both viruses and diseases, including Huntington’s disease (a painful neurodegenerative condition), cancer, and congenital blindness, are already underway. Finally, Isaacson lists two other potential applications of CRISPR that could change the world: biohacking and bioweaponry.

Isaacson describes biohacking as a social movement aimed at democratizing biotechnology. One well-known biohacker, Josiah Zayner, sells CRISPR technology kits online, which enables anyone with the funds to buy one to do their own gene editing experiments—for example, one kit enables you to make bacteria bioluminescent. Zayner once publicly injected himself with a CRISPR solution to demonstrate his belief that everyone should have access to this technology. One benefit of expanding access is that as more people work with CRISPR, advancements will be made more quickly. But Isaacson implies that biohacking may also have serious risks.

(Shortform note: The term “biohacking” doesn’t exclusively refer to the movement to democratize biotechnology; the term is also applied to other ways of optimizing human life, including diets like intermittent fasting and injections with performance enhancement drugs. Zayner has expressed remorse about the self-injection stunt he pulled, since he fears that biohackers will push themselves beyond normal limits to conduct harmful self-experiments. This admission sheds some light on the serious risks associated with biohacking—the culture of the movement is such that participants are competing with each other to become the best. The dangers associated with biohacking led California to pass the first law regulating the practice.)

Finally, Isaacson explains that many officials worry that CRISPR technology could be used to engineer bioweapons. For this reason, the US Department of Defense (DoD) sponsors research on anti-CRISPRs: naturally occurring systems that help viruses overcome CRISPR defenses in bacteria. Some scientists, including Doudna, are working on creating and implementing anti-CRISPR technology that could be used to fend off a CRISPR-derived bioweapon. Isaacson also notes that the DoD is currently pursuing research on the use of genetic enhancements to create supersoldiers.

The Future of CRISPR Research

Since Isaacson published The Code Breaker in 2021, scientists have made several breakthroughs regarding CRISPR’s potential applications. Let’s review what’s changed since 2021 for some of the potential applications Isaacson mentions.

Scientists continue to develop CRISPR gene therapies for viruses and diseases. For example, research thus far has had promising results with regard to the treatment of sexually transmissible viruses like herpes, HPV, and hepatitis. Additionally, Chinese scientists have used CRISPR to deliver antiviral gene therapies to pigs to make their organs more suitable for implantation in humans, and CRISPR is being tested for its potential to enhance the effectiveness of cancer therapies in patients whose immune systems are too damaged to respond positively to the treatment.

Scientists are also applying CRISPR to non-human life forms. For example, an artist is using CRISPR to recreate the fragrances of extinct flowers, a Dalmatian breeder is using CRISPR to prevent health problems in his dogs, and scientists are using CRISPR to slow the extinction of honeybees. Perhaps most controversially, some scientists have used CRISPR to create chimeras—or mixed-species hybrids, usually involving monkeys or pigs—to assist with human disease treatment.

Scientists are also studying CRISPR’s potential purposes in warfare. Some scientists speculate that CRISPR could be used to create and spread viruses with a “zombification” effect and to create bioweapons out of snake venom. Others speculate that human DNA could be spliced with animal DNA to give soldiers advantageous traits like ultra-enhanced vision.

Finally, it’s important to know that scientists are working on enhancing not only CRISPR’s applications, but also the technology itself. For example, advancements in quantum biology and artificial intelligence have enabled scientists to better understand which gRNAs are most suitable for experiments in the cells of different species. As the technology improves, we can probably expect its applications to become more precise and far-ranging.