4.7: Genetic Testing and Genetic Engineering

Genetic Science Today

To assist with public health efforts, newborn screening for genetic diseases has been available in the United States for 50 years. One of the first available genetic tests was used to confirm a phenylketonuria (PKU) diagnosis in infants, a condition that is easily managed with a dietary change. Today, each state decides which genes are included on its newborn screening panel, and some states even have programs to help families navigate medical follow-up care.

Since those early days, the genetic testing industry has exploded. There are now hundreds of laboratories offering tests for a few thousand different genes, results than can inform medical decisions for both infants and adults. Both rapid improvement in sequencing technology and a steep drop in cost made this possible. Genetic testing has also moved out of the clinic and into everyday life. You can now order a DNA test online without seeing or consulting with medical professionals.

Clinical Testing

Clinical genetic tests help patients make medically informed decisions about family planning and health. Applications include support for in vitro fertilization (IVF), embryo genetic screening, and personalized medicine, such as matching cancer patients to therapies most likely to work for their specific tumor. Because the stakes are high, clinical laboratories in the United States must follow the Clinical Laboratory Improvement Amendments (CILA), a set of federal standards designed to ensure accurate results.

One major benefit of clinical genetic testing is access to genetic counselors who are professionals with specialized training in medical genetics and counseling. If someone has a family history of a genetic disease, a physician may recommend carrier screening to assess the risk of passing that condition on to a child. Genetic counselors help patients interpret results and provide support as they work through what can be emotionally difficult decisions.

Direct-to-Consumer (DTC) Genetic Testing

Direct-to-consumer (DTC) genetic testing—DNA testing purchased and used without a doctor or genetic counselor involved—has become hugely popular. Companies market these tests around the idea of personal empowerment: the more you know about your DNA, the better choices you can make. A test might flag a slightly elevated risk for celiac disease, prompting someone to try a gluten-free diet, or it might detect a pathogenic BRCA1 or BRCA2 variant linked to cancer risk, prompting a visit to a physician for follow-up clinical testing. DTC companies also sell tests purely for fun or lifestyle purposes, such as ancestry breakdowns or “personalized” fitness and nutrition reports.

Because DTC testing skips genetic counselors and faces looser regulation than clinical labs, it has generated real controversy. When the company 23andMe began offering health-related results in 2007, the FDA stepped in by 2013, concerned that customers were receiving complex medical information, like Alzheimer’s disease risk, without professional guidance to help interpret it. Critics worried this could create unnecessary anxiety, sometimes called the “burden of knowing,” or lead people to make medical decisions they didn’t fully understand. 23andMe eventually worked with the FDA to gain approval for a limited set of health reports, requiring customers to complete educational modules before viewing certain results. At the same time, some customers have used these results to seek out beneficial medical care they otherwise wouldn’t have pursued.

The 23andMe story took a dramatic turn in 2025, however, and it raises a cautionary question that goes beyond medical interpretation: what happens to your most intimate biological information when the company holding it goes out of business? After years of financial losses, a 2023 data breach that exposed the genetic and personal data of nearly 7 million users, and a workforce reduction of 40%, 23andMe filed for bankruptcy in March 2025 (Al-Hindi and Henn 2025). A U.S. bankruptcy court ruled that the company’s genetic database, containing information from roughly 15 million customers, could be sold as a corporate asset. Attorneys general in multiple states urged residents to delete their data immediately. The database was ultimately acquired for $305 million by TTAM Research Institute, a nonprofit created and controlled by 23andMe’s own co-founder. Legal scholars have since called the bankruptcy an “inflection point” for the DTC genetics industry, pointing out that current bankruptcy law contains no explicit protections for genetic data—meaning your DNA profile can legally change hands without your meaningful consent. The case has renewed calls for federal legislation that treats genetic data differently from other personal information (Branch 2025).

Ancestry tests raise a related set of concerns. They sort a customer’s DNA into population categories, but genetic variants rarely belong exclusively to one group, and the boundaries of these “populations” are defined by the companies themselves rather than by biology.

An allele labeled “Irish” for example, likely existed long before the country of Ireland did. Another consideration is that someone’s identity need not include biological relationships. In using these tests, customers do have the option to connect with newfound genetic relatives online which can be a wonderful experience for some people and a painful one for others.

Genetic Engineering: Editing the Code of Life

Genetic testing tells us what’s already written in an organism’s DNA. Genetic engineering goes a step further by changing DNA on purpose. This field has moved from science fiction to everyday reality astonishingly fast, and it raises some of the most important ethical questions in modern biology and society.

Genetically Modified vs. Genetically Engineered: What’s the Difference?

People often use “GMO” (genetically modified organism) and “genetically engineered” interchangeably, but it’s worth pulling these terms and processes apart.

Humans have been modifying the genetics of plants and animals for thousands of years through artificial selection by choosing which individuals get to reproduce based on traits we want. Cross-breeding corn varieties to get sweeter kernels, or breeding dogs or cats for specific traits, are both forms of genetic modification, but they work within a species’ existing gene pool and happen gradually over many generations.

Transgenic engineering, or genetically engineered organisms (GEOs), is something different. Scientists take a gene from one species, sometimes from a completely different kingdom of life, and insert it directly into another organism’s genome. One example comes from a genetically engineered salmon that contains a growth hormone gene from a Chinook salmon paired with a genetic “on switch” from an eel-like fish called the ocean pout, allowing it to grow to market size in about half the normal time (U.S. FDA AquAdvantage Salmon Fact Sheet, 2025).

More recently, gene editing tools like CRISPR have introduced a third category. Rather than inserting foreign DNA, CRISPR works like a precise pair of molecular scissors, allowing scientists to cut, delete, or rewrite an organism’s own genes. A non-browning mushroom approved in the U.S. a few years ago was created this way. Researchers simply switched off the gene responsible for browning without adding any new DNA at all. Because no foreign genes are introduced, gene-edited organisms like this one are often regulated quite differently than transgenic GEOs, which has sparked its own debate about whether existing labeling laws make sense (Waltz 2016).

Cloning: Copying Life

Cloning produces a genetically identical copy of an existing organism, most famously demonstrated with Dolly the sheep in 1996. While cloning captured the public imagination and inspired a number of science fiction thrillers, it has found a genuinely serious application in conservation biology.

Can Cloning Save an Endangered Species?

The black-footed ferret is North America’s only native ferret species and one of the continent’s most endangered mammals. By the 1980s, the entire surviving population descended from just seven individuals, leaving the species dangerously low on genetic diversity. Scientists at the San Diego Zoo Wildlife Alliance’s Frozen Zoo had preserved tissue from a ferret named Willa, who died in 1988 without leaving any descendants. Willa’s genetic material contained roughly three times more unique variations than found in the surviving population—a treasure trove of lost diversity sitting in a freezer for over three decades. Researchers used Willa’s preserved tissue to produce three clones. The first, Elizabeth Ann, was born in December 2020 as the first cloned endangered species native to North America. Her fellow clones, Antonia and Noreen, followed in May 2023. In June 2024, Antonia became the first cloned animal of any endangered species to successfully reproduce with a male black-footed ferret from an existing captive population, giving birth to two surviving kits. Unlike a clone, Antonia’s kits are not genetically identical to Willa. They carry Willa’s rare genetic material blended with that of their father, which is precisely the outcome conservationists were hoping for.

By summer 2025, four more litters had been born from Antonia, Noreen, and Antonia’s own offspring, bringing the total number of ferrets carrying Willa’s genes to 15 individuals. Sadly, both Elizabeth Ann and Noreen passed away in 2025, but the program continues through Antonia and her growing line of descendants. Willa’s story is a reminder that the tools of modern genetics and the dedication of conservation biologists, working together, can accomplish can turn the tide for species on the edge of extinction.

Sources:

Revive & Restore. (2025, November 4). Five Years Later: Black-footed ferret cloning success proves the power of intended consequences. https://reviverestore.org/five-years-later-black-footed-ferret-cloning-success-proves-the-power-of-intended-consequences/

Smithsonian National Zoo & Conservation Biology Institute. (2025, September 25). New Kits Born in Black-footed Ferret Cloning Research. https://nationalzoo.si.edu/news/new-kits-born-black-footed-ferret-cloning-research

U.S. Fish & Wildlife Service (2024, April 17). Innovative Cloning Advancements for Black-footed Ferret Conservation. https://www.fws.gov/press-release/2024-04/innovative-cloning-advancements-black-footed-ferret-conservation

Cloning has also become a commercial service. Companies now offer to clone people’s deceased pets (for a considerable price), which raises its own interesting question: does a cloned pet have the same personality as the original? As you’ve learned from epigenetics, that’s not necessarily the case.

De-Extinction: Can We Bring Back Extinct Species and Should We?

Cloning and gene editing are now bringing what once seemed like science fiction to life: the revival of extinct species. The company leading this effort is Colossal Biosciences, a biotech firm valued at $10 billion and whose tagline, “Forever is Temporary,” signals just how ambitious its goals are. Colossal has announced projects targeting the woolly mammoth, the dodo, and the Tasmanian tiger.

Their most headline-grabbing achievement to date involves the dire wolf, a large predator that roamed the Americas during the last ice age before going extinct roughly 10,000 years ago. In April of 2025, Colossal announced the births of three pups named Romulus, Remus, and Khaleesi, whose gray wolf DNA had been edited in some places and designed in others to mimic gene expressions found in ancient dire wolf DNA extracted from a preserved tooth and skull. The resulting animals display several dire wolf traits, including distinctively shaggy white fur.

But are they really dire wolves? Most scientists say not, or at least, not exactly. As one paleogeneticist put it, what Colossal produced is essentially a genetically engineered designer gray wolf. This distinction matters because if de-extinction is real, then extinction is no longer permanent. This has some conservationists worried that this could reduce public urgency around protecting species that are endangered right now. Indigenous scholars have raised additional concerns: from a Māori perspective rooted in the concept of kaitiakitanga—humanity’s duty to care for the natural world—recreating a species without first healing the environment and communities it was part of misses the point entirely (Golembiewski 2026).

Colossal’s chief science officer, Beth Shapiro, pushes back on the idea that de-extinction competes with conservation. She argues that the excitement generated by these projects has attracted investment in tools that are actively helping save elephants, corals, and other living species. At the same time, behavioral scientists studying public attitudes caution that the spectacle of “bringing back” a dramatic extinct animal might give people the false impression that extinction is reversible—a misunderstanding that a 2023 global survey found already existed in roughly half of respondents, before the dire wolf announcement.

The debate over de-extinction is, at its core, a debate about what we owe the natural world, how we define a species, and whether technological ingenuity can substitute for the harder work of protecting ecosystems in the first place.

Gene-Edited and “Designer” Babies

The most ethically charged frontier of genetic engineering involves editing the genomes of human embryos. It’s important to distinguish between two very different applications here.

Somatic gene editing changes the DNA of a living person’s cells but is not passed on to their children. In 2025, doctors at Children’s Hospital of Philadelphia used a custom-designed CRISPR therapy to correct a life-threatening metabolic mutation in an infant known as “KJ,” who was born with a rare condition in which the liver cannot properly process ammonia, allowing it to build up to toxic levels. KJ received his first infusion of the personalized therapy in February 2025, making him the first person in history to receive a customized gene editing drug designed specifically for his individual genetic variant (Musunuru, et al. 2025; The Economist, 2025). By February 2026, one year later, KJ had achieved meaningful milestones including walking and talking, and continues to grow (Children’s Hospital of Philadelphia, 2026). This kind of personalized gene therapy is increasingly seen as a legitimate medical treatment, similar in principle to other advanced therapies, though still extraordinarily expensive and currently available to very few patients.

Germline editing, by contrast, alters the DNA of an embryo, sperm, or egg in a way that would be inherited by all future generations. This is where “designer babies” enter the conversation. In 2018, Chinese scientist He Jiankui announced that he had used CRISPR to edit the embryos of twin girls, attempting to make them resistant to HIV. The scientific community reacted with near-universal condemnation and He was sentenced to prison for violating research ethics regulations (McCurry 2024).

You might think that scandal would end the conversation, but it hasn’t. New biotech startups announced plans to pursue embryo editing research, driven mostly by interest from tech billionaires (The Economist, 2025). Most scientists agree that the techniques still aren’t safe or well-understood enough for clinical use, and a number of countries have banned reproductive germline editing outright. But the debate over whether and when it might ever be appropriate for preventing genetic diseases versus selecting to enhance traits like intelligence, or appearance, is very much alive.

Big Business, Big Questions

Genetic engineering is now a massive global industry, spanning agriculture, pharmaceuticals, conservation, and reproductive medicine. Across the examples we’ve explored here, the same fundamental ethical questions tend to arise:

Safety and unintended consequences. Editing DNA can have effects beyond the targeted gene, and our understanding of how genes interact with each other and the environment is still incomplete.

Access and equity. Advanced genetic therapies and reproductive technologies are expensive. If only wealthy individuals can access embryo selection or genetic enhancement, could this widen existing social inequalities or even create new forms of biological inequality?

Consent across generations. Germline edits don’t just affect one person; they’re passed down to children, grandchildren, and beyond, none of whom can consent to the change.

Where do we draw the line? Most people would be comfortable with using genetic technology to treat or prevent serious disease. Far fewer might be comfortable using it to select for traits like eye color, height, or athletic ability, yet the same underlying tools could potentially do both. Drawing that line, and deciding who gets to draw it, is as much a question for anthropologists, bioethicists, and policymakers as it is for scientists.

As you continue through this course, keep these themes in mind. Understanding how DNA works—and how we’re increasingly able to read, copy, and rewrite it—is essential not only for understanding evolution and human variation (covered in the chapters ahead), but for thinking critically about the kind of future we want these technologies to help build.