Science
1 gene, 1 disease no more – acknowledging the full complexity of genetics could improve and personalize medicine
Genetic disease development is influenced by multiple variants, not just a single mutation. Research indicates that primary mutations interact with secondary variants, affecting symptom severity. This complexity necessitates broader genomic understanding for better disease prediction and personalized medical care.
Last Updated on October 13, 2025 by Daily News Staff
Santhosh Girirajan, Penn State
Genetic inheritance may sound straightforward: One gene causes one trait or a specific illness. When doctors use genetics, it’s usually to try to identify a disease-causing gene to help guide diagnosis and treatment. But for most health conditions, the genetics is far more complicated than how clinicians are currently looking at it in diagnosis, counseling and treatment.
Your DNA carries millions of genetic variants you inherit from your parents or develop by chance. Some are common variants, shared by many people. Others are rare variants, found in very few people or even unique to a family. Together, these variants shape who you are – from visible traits such as height or eye color to health conditions such as diabetes or heart disease.
In our newly published research in the journal Cell, my team and I found that a genetic mutation involved in neurodevelopmental and psychiatric conditions such as autism and schizophrenia is affected by multiple other genetic variants, changing how these conditions develop. Our findings support the idea that, rather than focusing on single genes, taking the whole genome into account would provide insight into how researchers understand what makes someone genetically predisposed to certain diseases and how those diseases develop.
Primary and secondary variants
Certain rare variants can cause problems on their own, such as the genetic mutations that cause sickle cell anemia and cystic fibrosis. But in many cases, whether someone actually develops symptoms of disease depends on what else is happening across the genome.
While a primary variant might trigger a disease, secondary variants can alter how that disease develops and progresses. Think of it like a song: The melody (primary variant) is the main part of the song, but the bassist and drummer (secondary variants) can change its groove and rhythm.
That’s why two people with the same genetic mutation can seem so different. One person might have severe symptoms, another person mild symptoms, and another none at all. These variations can even occur within the same family. This phenomenon, called variable expressivity, arises from differences in the secondary variants a person has. In most cases, these variants amplify the effects of the primary mutation. A higher number of secondary variants on top of a primary variant generally leads to more severe disease. https://www.youtube.com/embed/D0XYWKm_LoM?wmode=transparent&start=0 Mutations are a source of genetic variation.
Sometimes, a primary variant and a secondary variant together can cause two different disorders in the same person, such as Prader-Willi syndrome and Pitt-Hopkins syndrome. Other times, secondary variants have no obvious effect on their own but together can tip the balance of whether and how a disease will appear, even in the absence of a primary variant. This can be seen in the development of heart disease in children.
Insights from a missing piece of a chromosome
My team and I studied a genetic change known as a 16p12.1 deletion, where a small piece of chromosome 16 is missing. Researchers have linked this mutation to developmental delay, intellectual disability and psychiatric conditions such as schizophrenia. Yet most children inherit this genetic variant from a parent who has milder symptoms, different symptoms or sometimes no symptoms at all.
To understand why this happens, we analyzed 442 individuals from 124 families carrying this genetic mutation. We found that children lacking this piece of chromosome 16 had more secondary variants elsewhere in the genome compared to their carrier parents. These secondary variants took many forms, including both small changes and large deletions, duplications and expansions of their DNA.
Each type of secondary variant was associated with different health outcomes. Some were linked to smaller head size and reduced cognitive function, while others contributed to higher rates of psychiatric or developmental symptoms. This suggests that while a 16p12.1 deletion makes the genome more sensitive to neurodevelopmental disorders, which symptoms manifest depends on which other variants are present.
The story gets even more complex when considering the fact that children not only inherit a 16p12.1 deletion from one parent but also inherit secondary variants from both parents.
My team and I found that the symptoms of the parent with this genetic mutation often match those of their spouse. For example, a parent with a 16p12.1 deletion who shows signs of anxiety or depression is more likely to have a partner who also has these symptoms. This pattern, called assortative mating, means that when parents with overlapping genetic risks have children, those risks can combine and accumulate.
Over generations, this stacking of secondary variants can lead to children who have more severe symptoms than their parents.
Biases in genetics research
One reason why scientific understanding of secondary variants has lagged is that genetic research often depends on who is recruited to participate in these studies and how researchers recruit them.
Most studies recruit patients affected with a particular disease. Families recruited from genetic clinics typically have children with severe versions of the disease. But if studies focus only on patients with the most acute symptoms, researchers may overestimate the effects of primary variants and miss the subtler role that secondary variants may play in how a disease develops.
But if researchers were to study people drawn from the general population – say, by recruiting people from a large shopping mall – some might carry the same primary variant but have far milder symptoms or none at all. This variability allows researchers to better dissect how different parts of the genome interact with each other and affect how a disease develops.
In our study, for example, we found that people with a 16p12.1 deletion who were recruited from the general population often had milder symptoms and different patterns of secondary variants compared to those who were recruited in a clinic.
Embracing complexity in genetics
Instead of a deterministic view where one mutation equals one outcome, a more complex model accounts for the fact that whether and how a disease develops depends on the interplay between different genetic variants and environment. This has implications for how genetics is used in the clinic.
Currently, a child who tests positive for a genetic variant might be diagnosed with a disease tied to that mutation. In the future, doctors might also examine the child’s broader genetic profile to better predict their developmental trajectory, psychiatric risk or response to therapies. Families could be counseled with a more realistic picture of their child’s probability of developing a disease, rather than assuming every person with the same genetic variant will share the same outcome.
The science is still emerging. Larger and more diverse datasets and models that can better capture the subtle effects of genetic variants and environmental factors are still needed. But what’s clear is that secondary variants are not secondary in importance.
By embracing this complexity, I believe genetics can move closer to its ultimate promise: not just explaining why disease happens, but predicting who is most at risk and personalizing care for each individual.
Santhosh Girirajan, Professor of Biochemistry, Molecular Biology and Genomics, Penn State
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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health and wellness
Lactose intolerance is actually the human norm – but racism, the US government and business interests have made it into a condition
Lactose intolerance is the global human norm, but Western dietary standards, government policies and commercial interests helped frame it as a medical deficiency.
Hilary Smith, University of Denver
Lactose intolerance makes drinking milk or eating ice cream a literal pain. For some people, eating a dairy treat can lead to bloating, nausea and diarrhea. You might’ve experienced its effects yourself. If so, you may think of lactose intolerance as a defect rather than the norm.
But did you know that most people in the world today are lactose intolerant – and that the condition itself was invented in the 1960s?
“Surely you mean discovered, not invented,” I hear you saying. I don’t. As a historian who has traced the origins of nutrition-science ideas, I have chosen the word “invented” on purpose.
Inventing lactose intolerance
Variations in people’s ability to digest lactose first came to scientists’ attention after American dairy producers found a way to rid themselves of a postwar milk surplus. To offload what they couldn’t sell, they looked to the government to intervene. And it did, buying the excess and embedding it in school lunches and other places with publicly funded meals.
Suddenly, many people who had not habitually drunk milk were consuming it regularly, including not only some Americans but also people overseas. Part of that same milk surplus found its way into school lunches in places such as Japan and Taiwan in the 1950s as the American government began to sell milk to allies during the Cold War.
Many of the groups drinking milk regularly for the first time did not like it. In fact, it made them feel sick. Intrigued, scientists set up experiments to figure out why. In a 1966 study comparing how Black and white people incarcerated in Baltimore metabolized lactose, researchers found that Black participants had lower levels of lactase – the enzyme that breaks down lactose – in their guts.
To the white scientists conducting this study, the trouble that the Black prisoners had digesting milk looked like an “inborn error of metabolism.” They assumed that the normal human state was lactose tolerance and that the lactose intolerant had inherited a genetic mutation.
It was only after years more work with research participants of many races that experts realized that, as one National Institutes of Health official put it in 1981, “lactose intolerance is a normal physiological condition, shared by every adult animal except for certain ethnic and racial groups in man.” People of northern European descent, it turned out, were the weird ones. It was their ancestors who had passed down a genetic mutation – one that made them able to digest milk after infancy.
In short, what scientists discovered in the 1960s was that different bodies process milk differently. What they invented was the idea that lactose intolerance is a defect. Accepting that framing would mean nearly two-thirds of the human population – the estimated prevalence of lactose intolerance worldwide – is defective.
Instead of acknowledging that dairy-free diets can be healthy, people innovated ways to overcome this supposed disability so everyone could consume more.
Nutritional imperialism
Lactose intolerance is one example of what I call nutritional imperialism: a way of thinking that treats white diets as the norm and everyone else’s as an aberration.
Nutritional imperialism was common in the 20th century, when scientists thought that not only milk-rich but also meat-heavy diets were best; they considered diets outside of the United States and Europe too vegetarian. Some also argued that wheat flour, not rice, ought to be the universal staple.
The same bias applied to bodies. Besides faulty lactose digestion, nonwhite bodies were accused of other failures, too, such as aldehyde dehydrogenase deficiency, an inability to digest alcohol quickly. The less technical term for this may be more familiar: Asian flush.
Such differences might have been thought of as variety, just another way of being human. Instead, each became a deficiency.
Many people today have inherited and perpetuated this way of thinking without knowing it, including those who are deemed deficient by it. In 1959, the director of Japan’s nutrition bureau declared that “rice-eating peoples” such as the Japanese were “resigned and passive” and could correct this by imitating Western diets and switching to wheat.
Today, the most prominent scientist promoting the idea that Asian flush is a disease is a geneticist of Taiwanese descent who started a research consortium to study “the most common human enzymopathy in the world.”
The Chinese Nutrition Society placed a tall glass of milk next to its 2022 Food Guide Plate – never mind estimates that the vast majority of Han Chinese, the largest ethnic group in China and worldwide, are lactose intolerant.
Turning sickness back into difference
Science that pathologizes difference helps racism persist.
In recent years, white supremacists have embraced the concept of lactose intolerance as a distinguishing debility of nonwhite people. Social media users have copied and pasted a map of the geographic distribution of lactose tolerance originally published in the scientific journal Nature into racist chat threads on the online discussion forum 4chan.
In 2017, internet trolls disrupted an anti-racist art installation with neo-Nazi chants and messily downed jugs of milk to accentuate their white identity.
Turning a lactose-digestion difference into a deficiency has done more to reinforce narratives of racial hierarchy than to improve public health. So here’s a suggestion: If you enjoy eating dairy, keep doing it; if you don’t, don’t – and know that there is nothing wrong with you.
Hilary Smith, Professor of History, University of Denver
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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News
FAA Certifies Boeing 737-7: What It Means for Airlines and the 737 MAX Program
The FAA has certified Boeing’s new 737-7, clearing the smallest 737 MAX variant for service as Boeing and Southwest prepare for first deliveries.
The U.S. Federal Aviation Administration has certified Boeing’s new 737-7, granting the company an amended type certificate that clears the smallest member of the 737 MAX family for commercial service. The milestone closes a multi-year certification effort and puts the focus on execution: Boeing and launch customer Southwest Airlines say preparations are underway to support first deliveries.
For STM Daily News readers, the headline isn’t just “another plane gets approved.” It’s a signal that Boeing has now cleared a key MAX variant designed for long-range flexibility in a smaller footprint—an aircraft type airlines can use to open or defend routes where demand is strong, but not strong enough to justify a larger narrowbody.
What FAA certification means
An amended type certificate means the FAA has approved the 737-7’s design as compliant with commercial aviation regulations. In practical terms, certification allows airlines to place the aircraft into revenue service once deliveries begin and operator-specific steps—training, manuals, maintenance programs, and entry-into-service planning—are completed.
Boeing also said the FAA updated Boeing Production Certificate No. 700 (PC 700) to include the 737-7, supporting production and delivery activities.
Why the 737-7 matters in the MAX lineup
Boeing positions the 737-7 as the smallest and longest-range member of the 737 MAX family. The company says it typically seats 135 to 160 passengers in a two-class configuration and offers a range of up to 3,800 nautical miles (7,040 km). That combination matters because it gives airlines more options to fly longer “thin” routes—markets where frequency and reach matter more than packing in additional seats.
Boeing also highlights performance for operations out of high-altitude airports and in hot climates, where takeoff performance and payload-range tradeoffs can shape fleet decisions.
Efficiency claims: fuel, emissions, and noise
Boeing says the 737-7, like other 737 MAX jets, reduces fuel use and CO2 emissions by 20% and cuts the noise footprint by 50% compared to the airplanes it typically replaces. For airlines, those improvements typically show up in two ways:
- Route economics: lower fuel burn can improve margins on longer sectors and reduce exposure to fuel-price swings.
- Operational constraints: quieter aircraft can help with airport noise requirements and community pressure, while lower emissions support sustainability targets.
Inside the certification effort
Boeing said the certification program began in 2018 and included more than 1,000 hours of flight and ground testing, extensive system safety analysis, and human factors reviews. The company also noted an updated engine anti-ice system to address a potential condition discovered during flight testing.
Boeing Commercial Airplanes President and CEO Stephanie Pope called the certification “important” validation of the airplane’s design and the work of the MAX development team. Mike Sinnett, senior vice president of Product Strategy, Product Development and Development Programs, said Boeing held regular discussions with the FAA and that the process has sharpened the company’s understanding of current regulatory requirements—knowledge Boeing expects will accelerate future development with a renewed emphasis on human factors, safety, and quality.
What to watch next
With certification complete, the next phase is about delivery timing and real-world deployment.
- First deliveries to Southwest: Boeing and Southwest are preparing for delivery of the first airplane, including updates to final configuration.
- Production stability: certification removes a major hurdle, but supply chain health and production cadence will determine how quickly the 737-7 shows up in airline schedules.
- The 737-10 timeline: Boeing reiterated it is working to certify the 737-10 this year, keeping attention on how quickly the final MAX variant clears regulatory review.
The bigger MAX picture
Boeing said the 737 MAX family order book stands at more than 7,200 airplanes, with more than 2,300 delivered through the end of June 2026. The 737-7’s certification adds another deliverable product to that portfolio—one aimed at airlines that want long range without stepping up to a larger gauge.
Bottom line
FAA certification of the 737-7 is a meaningful milestone for Boeing and for airlines looking for a smaller narrowbody with long-range capability. The real test now is operational: turning certification into on-time deliveries and reliable entry into service—while the industry watches Boeing’s push to certify the 737-10.
Related Links
- Boeing 737 MAX family overview (manufacturer background/specs): https://www.boeing.com/commercial/737max/
- FAA Aircraft Certification (how type certification works): https://www.faa.gov/aircraft/air_cert/
- FAA Airworthiness Directives (regulatory actions database): https://www.faa.gov/regulations_policies/airworthiness_directives
- Southwest Airlines newsroom (launch customer context / fleet updates): https://www.swamedia.com/
- Boeing Commercial Airplanes newsroom (for follow-ups and official updates): https://boeing.mediaroom.com/news-releases?item=130821
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Source:
Boeing (PRNewswire), Aug. 3, 2026 — “U.S. FAA certifies new Boeing 737-7 airplane.”
Nature
What in the Heck Is a Sweat Bee? Turns Out, My Wife Wasn’t Making It Up
My wife Rebecca said she thought a sweat bee stung her. I thought she was making it up. Turns out, sweat bees are very real—and their strange name actually makes perfect sense.
It started with a conversation with my wife, Rebecca.
She mentioned that she thought she’d been stung by something called a “sweat bee.”
My immediate reaction was basically:
“What in the heck is a sweat bee?”
I’ll admit it. For a moment, I thought she was making the whole thing up. 😂
A sweat bee? Really?
It sounded like one of those names somebody invents when they don’t know what actually stung them.
“It wasn’t a regular bee. It was a… uh… sweat bee!”
So naturally, I asked ChatGPT the same question: What in the heck is a sweat bee?
Well, Rebecca gets this round.
Sweat bees are absolutely real.
And Yes, They’re Interested in Your Sweat
Sweat bees belong primarily to the Halictidae family, a large group of generally small bees found around the world.
Some are rather ordinary-looking little insects, while others are surprisingly flashy, sporting metallic shades of green, blue, bronze or gold.
But here’s where they earned that wonderfully unfortunate name.
Some sweat bees are attracted to human perspiration.
They’re not after you because they’re angry, and they’re certainly not tiny vampire bees. They’re interested in the salt and minerals in your sweat.
In other words, after you’ve been outside working, gardening, exercising or simply trying to survive a hot summer afternoon, a sweat bee may look at you and think:
“Hey! Free electrolytes!”
Wait…They Can Sting Too?
Unfortunately for Rebecca, there’s another part of her story that checks out.
Female sweat bees can sting.
They’re generally not aggressive and aren’t flying around looking for people to attack. But if one gets trapped against your skin, squeezed or swatted, it may defend itself.
Their sting is generally considered relatively mild compared with those of many other bees and wasps—but “relatively mild” probably isn’t much consolation when you’re the person who just got stung.
So, Rebecca, I officially withdraw my skepticism.
Mostly.
Don’t Declare War on Them
As annoying as having a tiny bee land on your sweaty arm might be, sweat bees are actually beneficial insects.
They’re important pollinators, visiting wildflowers, garden plants and agricultural crops and carrying pollen from flower to flower.
So if one lands on you, gently brushing or blowing it away is probably a better idea than swatting it against your skin.
And that’s today’s unexpected nature lesson.
Sweat bees are real.
They really are attracted to sweat.
The females really can sting.
And, perhaps most importantly…
My wife was right.
There. I said it.
I’m sure I’ll never hear the end of this one. 😂
Related Links
- University of Arizona Cooperative Extension — Arizona Bee Identification Guide — A useful Arizona-focused guide that includes sweat bees and explains their appearance, size, nesting behavior and attraction to salt in perspiration.
- USDA Natural Resources Conservation Service — Native Bees and Their Favorite Flowers — More information about native pollinators and the important role sweat bees play around wildflowers.
- USDA Forest Service — Bee Basics — A broader guide to North American bees, including the colorful metallic members of the sweat bee family.
- Smithsonian National Museum of Natural History — Sweat Bee — See an actual female sweat bee specimen (Augochlorella aurata) and its scientific classification.
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