What Is a GMO?

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If you've followed the debate about GMOs with any sort of regularity, there's a strong chance you've come across a picture of a tomato stabbed by a giant syringe. That image, though a complete fiction, seems to perfectly capture what's preventing public acceptance of these foods: We don't really know what makes something a GMO.

GMOs aren't made with syringes and, at the moment, they aren't even made with tomatoes, at least not commercially. But that false image is everywhere, and surveys indicate consumers fear GMOs without knowing much about them.

So what exactly is a GMO?

FROM THE FIRST SWEET POTATO TO THE QUEEN'S CORGI

The initialism stands for "genetically modified organism," but it's a term lacking scientific precision. Moreover, it's hard to find an organism in any way connected to humans that hasn't been genetically modified, says Alison Van Eenennaam, a geneticist at UC-Davis who specializes in animal biotechnology. "I might argue that a great Dane or a Corgi are 'genetically modified' relative to their ancestor, the wolf," she tells Mental Floss. "'GMO' is not a very useful term. Modified for what and why is really the more important question.”

GMOs are often described as if they were a recent invention of our industrial food system, but genetic modification of food isn't new at all. It's been happening for many millennia: As long as farmers have been saving high-performing seeds for future harvests, we've had GMOs. Perhaps the earliest known example of a GMO is the sweet potato, which scientists believe became modified when wild sweet potatoes became infected, quite naturally, by a particular kind of soil bacteria. Realizing these sweet potatoes were edible, people began saving the seeds and cultivating them for future harvests. That was about 8000 years ago.

These days, when people say "GMO," they tend to mean one particular modification method that scientists refer to as transgenesis. As Van Eenennaam explains, transgenesis is "a plant-breeding method whereby useful genetic variation is moved from one species to another using the methods of modern molecular biology, also known as genetic engineering."

Transgenic crops and animals have been modified with the addition of one or more genes from another living organism, using either a "gene gun," Agrobacteria—a genus of naturally occurring bacteria that insert DNA into plants—or electricity, in a process called electroporation.

The first commercial transgenic crops debuted in the early 1990s: a virus-resistant tobacco in China [PDF] and the Flavr-Savr tomato in the U.S., which was genetically altered to not get "squishy." (It's no longer on the market.)

As to the health risks of GMO foods, the scientific consensus is clear: Transgenic crops are no riskier than other crops. Van Eenennaam points to a 20-year history of safe use that includes "thousands of studies, eleven National Academies reports, and indeed [the consensus of] every major scientific society in the world."

THE ROLE OF HERBICIDES AND PESTICIDES

Today, the most ubiquitous transgenic crops in the U.S. food system are cotton, soybeans, and corn, including those modified to resist the effects of the herbicide Roundup. Branded "Roundup Ready," these crops have been modified so that farmers can apply the herbicide directly to crops to control weeds without killing the crops themselves.

For farmers, the result was better weed control and higher yields. For critics of GMOs, these crops became their smoking gun. These opponents argue they're bad for the planet and bad for our health.

There's no question that use of glyphosate, the active ingredient in the herbicide Roundup, has increased since the introduction of GMOs, but measuring its environmental impact is a far more complex equation. For example, as glyphosate use has increased, so has the prevalence of conservation tillage, a beneficial agricultural approach that helps sequester carbon in the soil and mitigate the impacts of climate change.

Bt crops—transgenic crops modified with genes from the all-natural bacterial toxin Bt, short for Bacillus thuringiensis—have also reduced the use of insecticide, according to a 2016 National Academies of Science report.

And though evidence suggests herbicide use has increased since Roundup Ready GMOs were first commercialized in the U.S., herbicide use has increased amongst some non-GMO crops, too. Glyphosate also replaced more toxic herbicides on the market and, if farmers were to stop using it, many would likely replace glyphosate with another herbicide, possibly one that's more toxic. Glyphosate-resistant weeds are a problem, but banning glyphosate, or glyphosate-resistant GMOs for that matter, wouldn't solve the problem.

In recent years, opponents of GMOs have increasingly aimed their fire at glyphosate. The source of many of these claims is a 2015 assessment [PDF] by the International Agency for Research on Cancer (IARC) to categorize glyphosate as "probably carcinogenic." That categorization has been hotly contested by many scientists, as other governmental agencies have concluded glyphosate does not pose a carcinogenic hazard. And, in June, reporting revealed that the lead researcher at IARC withheld important studies from the research group's consideration.

Weighing criticisms of glyphosate against its benefits certainly brings up complex issues in our agricultural system, but ultimately these issues are not unique to GMOs nor would they magically disappear if transgenic technology were eliminated altogether.

OTHER METHODS OF GENETIC MODIFICATION

Most consumers probably can't name all the different methods of genetic modification, but there's a good chance they've eaten foods modified by one of these methods all the same. Layla Katiraeea human molecular geneticist at Integrated DNA Technologies and a science communicator, has written about these methods to illustrate why it makes little sense to single out transgenic crops. Examples include polyploidy, which gave us the seedless watermelon, and mutagenesis, which scientists used to engineer a brightly colored grapefruit. As Katiraee points out, sometimes two different methods can even create a very similar end result. For example, the non-browning Opal apple was developed using traditional cross-breeding, while the non-browning Arctic apple uses transgenic methods to silence the genes that control browning.

Katiraee says the most common objections to GMOs aren't exclusive to transgenic crops: “Don't like ‘Big Ag'? They use all methods of crop modification. Don't like herbicide-tolerant crops? They've been made with other methods. Don't like patents? Crops modified by all methods are patented. If you go through the list, you won't find one [objection] that applies exclusively to transgenesis.”

Katiraee's arguments illustrate why it doesn't make sense to label transgenic crops "GMO" while omitting the non-browning opal apple or a seedless watermelon. And the non-GMO label can often be misleading. Van Eenennaam points to one of the more ridiculous examples: non-GMO salt. "Salt doesn't contain DNA, so salt cannot be genetically engineered," she says. "All salt is 'non-GMO' salt."

DISEASE-RESISTANCE SUCCESSES

The noisy GMO debate has often overshadowed the successes of lesser known, disease-resistant GMOs. Van Eenennaam argues that no one should object to these crops since protecting “plants and animals from disease aligns with most everyone's common interest in decreasing the use of chemicals in agricultural production systems, and minimizing the environmental footprint of food production." Examples include ringspot virus–resistant papaya in Hawaii [PDF] and the American chestnut, both rescued from the devastating effects of lethal plant viruses.

Disease-resistant crops often face an uphill battle for approval. In Uganda, scientists developed a disease-resistant banana that then faced difficult regulatory obstacles until a new law was finally approved in October by the country's Parliament. In Florida, where the disease called citrus greening has caused widespread crop damage and loss to the citrus industry, orange trees have been modified with a spinach gene to help crops resist the virus. But orange juice manufacturers will have to persuade consumers to buy it. 

Scientists have used transgenic modification to address health concerns too. For example, some variations of the wilt-resistant banana also include a boost of vitamin A. Scientists are working on a form of wheat that would be safe for people with celiac disease.

Van Eenennaam fears the controversy over GMOs has meant that, over the years, the public has missed out on important technologies. In the field of animal biotechnology, for example, animals have been produced that are resistant to disease, "that produce less pollution in their manure, [and] that have … elevated levels of omega-3 fatty acids," but none of these have been commercialized in the U.S.

Given that these crops and animals have a 20-year history of safe use, Van Eenennaam argues there's no reason that "fungus-resistant strawberries, disease-resistant bananas, and virus-resistant animals [should] sit on the shelf" unused.

Editor's note: This post has been updated. 

How Are Vaccines Made?

Eugeneonline/iStock via Getty Images
Eugeneonline/iStock via Getty Images

Vaccines have long been hailed as one of our greatest public health achievements. They can be made to protect us from infections with either viral or bacterial microbes. Measles and smallpox, for example, are viruses; Streptococcus pneumoniae is a bacterium that causes a range of diseases, including pneumonia, ear and sinus infections, and meningitis. Hundreds of millions of illnesses and deaths have been prevented due to vaccines that eradicated smallpox and significantly reduced polio and measles infections. However, some misunderstanding remains regarding how vaccines are made, and why some scary-sounding ingredients [PDF] are included in the manufacturing process.

The production of our vaccines has evolved a lot since the early days, when vaccination was potentially dangerous. Inoculating an individual with ground-up smallpox scabs usually led to a mild infection (called "variolation"), and protected them from acquiring the disease the "regular" way (via the air). But there was always a chance the infection could still be severe. When Edward Jenner introduced the first true vaccination with cowpox, protection from smallpox became safer, but there were still issues: The cowpox material could be contaminated with other germs, and sometimes was transmitted from one vaccinated person to another, leading to the inadvertent spread of blood-borne pathogens. We’ve come far in the last 200 years.

There are different kinds of vaccines, and each requires different processes to move from the laboratory to your physician's office. The key to all of them is production of one or more antigens—the portion of the microbe that triggers a host immune response.

Live Attenuated Vaccines and Dead, "Inactivated" Vaccines

There are several methods to produce antigens. One common technique is to grow a virus in a cell culture. Typically grown in large vats called bioreactors, living cells are inoculated with a virus and placed in a liquid growth medium that contains nutrients—proteins, amino acids, carbohydrates, essential minerals—that help the virus grow in the cells, producing thousands of copies of itself in each infected cell. At this stage the virus is also getting its own dose of protective medicine: antibiotics like neomycin or polymyxin B, which prevent bacterial and fungal contamination that could kill the cells serving as hosts for the virus.

Once a virus completes its life cycle in the host cell, the viruses are purified by separating them from the host cells and growth media, which are discarded. This is often done using several types of filters; the viruses are small and can pass through holes in the filter that trap larger host cells and cell debris.

This is how "live attenuated vaccines" are created. These vaccines contain viruses that have been modified so that they are no longer harmful to humans. Some of them are grown for many generations in cells that aren't human, such as chicken cells, so that they have mutated to no longer cause harm to humans. Others, like the influenza nasal mist, were grown at low temperatures until they lost the ability to replicate in the warmer temperatures of the lungs. Many of these vaccines you were probably given as a child: measles, mumps, rubella, and chickenpox.

Live attenuated vaccines replicate briefly in the body, triggering a strong—and long-lasting—response from your immune system. Because your immune system kicks into high gear at what it perceives to be a major threat, you need fewer doses of the vaccine for protection against these diseases. And unlike the harmful form of the virus, it is extremely unlikely (because they only replicate at low levels) that these vaccines will cause the host to develop the actual disease, or to spread it to other contacts. One exception is the live polio vaccine, which could spread to others and, extremely rarely, caused polio disease (approximately one case of polio from 3 million doses of the virus). For this reason, the live polio virus was discontinued in the United States in 2000.

Scientists use the same growth technique for "killed" or "inactivated" vaccines, but they add an extra step: viral death. Inactivated viruses are killed, typically via heat treatment or use of a chemical such as formaldehyde, which modifies the virus's proteins and nucleic acids and renders the virus unable to replicate. Inactivated vaccines include Hepatitis A, the injected polio virus, and the flu shot.

A dead virus can't replicate in your body, obviously. This means that the immune response to inactivated vaccines isn't as robust as it is with live attenuated vaccines; replication by the live viruses alerts many types of your immune cells of a potential invader, while killed vaccines primarily alert only one part of your immune system (your B cells, which produce antibodies). That's why you need more doses to achieve and maintain immunity.

While live attenuated vaccines were the primary way to make vaccines until the 1960s, concerns about potential safety issues, and the difficulty of making them, mean that few are attempting to develop new live attenuated vaccines today.

Combination, Bacterial, and Genetically Engineered Vaccines

Other vaccines aren't made of whole organisms at all, but rather bits and pieces of a microbe. The combination vaccine that protects against diphtheria, pertussis, and tetanus—all at once—is one example. This vaccine is called the DTaP for children, and Tdap for adults. It contains toxins (the proteins that cause disease) from diphtheria, pertussis, and tetanus bacteria that have been inactivated by chemicals. (The toxins are called "toxoids" once inactivated.) This protects the host—a.k.a. you, potentially—from developing clinical diphtheria and tetanus disease, even if you are exposed to the microorganisms. (Some viruses have toxins—Ebola appears to, for example—but they're not the key antigens, so they're not used for our current vaccines.)

As they do when developing live attenuated or inactivated vaccines, scientists who create these bacterial vaccines need some target bacteria to culture. But because the bacteria don't need a host cell to grow, they can be produced in simple nutrient broths by vaccine manufacturers. The toxins are then separated from the rest of the bacteria and growth media and inactivated for use as vaccines.

Similarly, some vaccines contain just a few antigens from a bacterial species. Vaccines for Streptococcus pneumoniae, Haemophilus influenzae type B, and Neisseria meningitidis all use sugars that are found on the outer part of the bacteria as antigens. These sugars are purified from the bacteria and then bound to another protein to enhance the immune response. The protein helps to recruit T cells in addition to B cells and create a more robust reaction.

Finally, we can also use genetic engineering to produce vaccines. We do this for Hepatitis B, a virus that can cause severe liver disease and liver cancer. The vaccine for it consists of a single antigen: the hepatitis B surface antigen, which is a protein on the outside of the virus. The gene that makes this antigen is inserted into yeast cells; these cells can then be grown in a medium similar to bacteria and without the need for cell culture. The hepatitis B surface antigen is then separated from the yeast and serves as the primary vaccine component.

Other Ingredients in Vaccines (and Why They're There)

Once you have the live or killed viruses, or purified antigens, sometimes chemicals need to be added to protect the vaccine or to make it work better. Adjuvants, such as aluminum salts, are a common additive; they help enhance the immune response to some antigens by keeping the antigen in contact with the cells of the immune system for a longer period of time. Vaccines for DTaP/Tdap, meningitis, pneumococcus, and hepatitis B all use aluminum salts as an adjuvant.

Other chemicals may be added as stabilizers, to help keep the vaccine working effectively even in extreme conditions (such as hot temperatures). Stabilizers can include sugars or monosodium glutamate (MSG). Preservatives can be added to prevent microbial growth in the finished product.

For many years, the most common preservative was a compound called thimerosal, which is 50 percent ethylmercury by weight. Ethylmercury doesn't stick around; your body quickly eliminates it via the gut and feces. (This is different from methylmercury, which accumulates in fish and can, at high doses, cause long-lasting damage in humans.) In 2001, thimerosal was removed from the vaccines given in childhood due to consumer concerns, but many studies have demonstrated its safety.

Finally, the vaccine is divided into vials for shipping to physicians, hospitals, public health departments, and some pharmacies. These can be single-dose or multi-dose vials, which can be used for multiple patients as long as they're prepared and stored away from patient treatment areas. Preservatives are important for multi-dose vials: bacteria and fungi are very opportunistic, and multiple uses increase the potential for contamination of the vaccine. This is why thimerosal is still used in some multi-dose influenza vaccines.

Though some of the vaccine ingredients sound worrisome, most of these chemicals are removed during multiple purification steps, and those that remain (such as adjuvants) are necessary for the vaccine's effectiveness, are present in very low levels, and have an excellent track record of safety.

The Science Behind Why the Earth Isn't Flat

Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.
Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.
NASA

On March 24, 2018, flat-earther Mike Hughes set out prove that the Earth is shaped like a Frisbee. The plan: Strap himself to a homemade steam-powered rocket and launch 52 miles into sky above California’s Mojave Desert, where he'd see Earth's shape with his own eyes.

It didn't matter that astronauts like John Glenn and Neil Armstrong had been to space and verified that the Earth is round; Hughes didn't believe them. According to The Washington Post, Hughes thought they were "merely paid actors performing in front of a computer-generated image of a round globe."

The attempt, ultimately, was a flop. He fell back to Earth with minor injuries after reaching 1875 feet—not even as high as the tip of One World Trade Center. For the cost of his rocket stunt ($20,000), Hughes could have easily flown around the world on a commercial airliner at 35,000 feet.

Hughes isn't alone in his misguided belief: Remarkably, thousands of years after the ancient Greeks proved our planet is a sphere, the flat-Earth movement seems to be gaining momentum. "Theories" abound on YouTube, and the flat-Earth Facebook page has some 194,000 followers.

Of course, the Earth isn't flat. It's a sphere. There is zero doubt about this fact in the real, round world. To say the evidence is overwhelming is an understatement.

HOT SPINNING BODIES

Not every celestial body is a sphere, but round objects are common in the universe: In addition to Earth and all other known large planets, stars and bigger moons are also ball-shaped. These objects, and billions of others, have the same shape because of gravity, which pulls everything toward everything else. All of that pulling makes an object as compact as it can be, and nothing is more compact than a sphere. Say, for example, you have a sphere of modeling clay that is exactly 10 inches in diameter. No part of the mass is more than 5 inches from the center. That's not the case with any other shape—some part of the material will be more than 5 inches from the center of the mass. A sphere is the smallest option.

Today the Earth is mostly solid with a liquid outer core, but when the planet was forming, some 4.5 billion years ago, it was very hot and behaved like more like a fluid—and was subject to the squishing effects of gravity.

And yet, the Earth isn't a perfect sphere; it bulges slightly at the equator. "Over a long time-scale, the Earth acts like a highly viscous fluid," says Surendra Adhikari, a geophysicist at the Jet Propulsion Laboratory in Pasadena, California. The Earth has been spinning since it was formed, and "if you have a spinning fluid, it will bulge out due to centrifugal forces." You can see evidence for this at the equator, where the Earth's diameter is 7926 miles—27 miles larger than at the poles (7899 miles). The difference is tiny—just one-third of 1 percent.

THE SHADOW KNOWS

The ancient Greeks figured out that Earth was a sphere 2300 years ago by observing the planet's curved shadow during a lunar eclipse, when the Earth passes between the Sun and the Moon. Some flat-Earth believers claim the world is shaped like a disk, perhaps with a wall of ice along the outer rim. (Why no one has ever seen this supposed wall, let alone crashed into it, remains unexplained.) Wouldn't a disk-shaped Earth also cast a round shadow? Well, it would depend on the orientation of the disk. If sunlight just happened to hit the disk face-on, it would have a round shadow. But if light hit the disk edge-on, the shadow would be a thin, straight line. And if the light fell at an oblique angle, the shadow would be a football–shaped ellipse. We know the Earth is spinning, so it can't present one side toward the Sun time after time. What we observe during lunar eclipses is that the planet's shadow is always round, so its shape has to be spherical.

The ancient Greeks also knew Earth's size, which they determined using the Earth's shape. In the 2nd century BCE, a thinker named Eratosthenes read that on a certain day, the people of Syene, in southern Egypt, reported seeing the Sun directly overhead at noon. But in Alexandria, in northern Egypt, on that same day at the same time, Eratosthenes had observed the Sun being several degrees away from overhead. If the Earth were flat, that would be impossible: The Sun would have to be the same height in the sky for observers everywhere, at each moment in time. By measuring the size of this angle, and knowing the distance between the two cities, Eratosthenes was able to calculate the Earth's diameter, coming up with a value within about 15 percent of the modern figure.

And when Columbus set sail from Spain in 1492, the question wasn't "Would he fall off the edge of the world?"—educated people knew the Earth was round—but rather, how long a westward voyage from Europe to Asia would take, and whether any new continents might be found along the way. During the Age of Exploration, European sailors noticed that, as they sailed south, "new" constellations came into view—stars that could never be seen from their home latitudes. If the world were flat, the same constellations would be visible from everywhere on the Earth's surface.

Finally, in 1522, Ferdinand Magellan's crew became the first people to circle the globe. Like Columbus, Magellan also set off from Spain, in 1519, heading west—and kept generally going west for the next three years. The expedition wound up back at the starting point (though without Magellan, who was killed during a battle in the Philippines). And speaking of ships and seafaring: One only needs to watch a tall ship sailing away from port to see that its hull disappears before the top of its mast. That happens because the ship is traveling along a curved surface; if the Earth were flat, the ship would just appear smaller and smaller, without any part of it slipping below the horizon.

THE EVIDENCE IS ALL AROUND (AND ALL ROUND)

But you don't need a ship to verify the Earth's shape. When the Sun is rising in, say, Moscow, it's setting in Los Angeles; when it's the middle of the night in New Delhi, the Sun is shining high in the sky in Chicago. These differences occur because the globe is constantly spinning, completing one revolution per day. If the Earth were flat, it would be daytime everywhere at once, followed by nighttime everywhere at once.

You also experience the Earth's roundness every time you take a long-distance flight. Jetliners fly along the shortest path between any two cities. "We use flight paths that are calculated on the basis of the Earth being round," Adhikari says. Imagine a flight from New York to Sydney: It would typically head northwest, toward Alaska, then southwest toward Australia. On the map provided in your airline's in-flight magazine, that might look like a peculiar path. But wrap a piece of string around a globe, and you'll see that it’s the shortest possible route.

"If the Earth were flat," Adhikari says, "the trajectory would be completely different." How different depends on which way the globe is sliced into a flattened map, but if it looked like it does on a Mercator-projection map, it might head east and pass over Africa.

Engineers and architects also take the Earth's curvature into account when building large structures. A good example is the towers that support long suspension bridges such as the Verrazano Narrows bridge in New York City. Its towers are slightly out of parallel with each other, the tops being more than 1.5 inches further apart than their bases. If the Earth were flat, the bottom of the towers would be separated by the exact same distance as the top of the towers; the planet's curvature forces the tops of the towers apart.

And for the last half-century, we've had eyewitness and photographic proof of the Earth's shape. In December 1968, the crew of Apollo 8 left Earth for the Moon. When they looked out of the Command Module windows, they saw a blue-and-white marble suspended against the blackness of space. On Christmas Eve, lunar module pilot William Anders snapped the famous "Earthrise" photograph. It gave us an awe-inspiring perspective of our round planet that was unprecedented in human history—but it wasn't a surprise to anyone.

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