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Is there any websites that provide the DNA sequences of food samples?

Is there any websites that provide the DNA sequences of food samples?


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We can get many DNA sequences at NCBI websites for free. Is there any websites that provide the DNA sequences of food especially meat, for free?

When I read papers regarding food authentication, they only stated the exact DNA sequence for the primers only, not the DNA sequence of their food samples. Why primers? Is it because scientists from the same field can guess what the sample's sequence will be?

Alternatively, if there's no site that shares the DNA sequence of food samples, is there any other place where I can get DNA sequence of mixed species or mutation? For free.


I am not aware of any websites that provide full DNA sequences for food products specifically. In the context of your question, by "food samples" I am assuming you are chiefly referring to meat, fish, and dairy products (the headline-making categories of food fraud), although similar principles are applied to plant products, oils, rice, and other natural products.

PCR

There are a wide variety of genetic techniques used to detect food fraud or adulteration. These techniques do not look at the entire genome of the animal or plant from which it is derived - that would be extremely expensive and unnecessary. Instead, scientists look at particular parts of the genome that they know will likely help them distinguish one species from another.

This is where the primers come in. DNA primers are short segments of DNA that are used to initiate replication of segment of DNA, and is the vital component of PCR that determines which part of the genome will be amplified. Once the PCR product is amplified, it can be analysed by a variety of techniques. For instance, if the PCR products of various species are known, they can simply be run on gel electrophoresis which separates the DNA products by size. Thus if a band of an unexpected size appears on the gel you know there has been some contamination. There are also more automated methods of detecting fragment size via electrophoresis.

Examples of where these techniques has been used has been to detect:

  • cow's milk in buffalo mozzarella cheese (López-Calleja et al., 2004)
  • king bolete mushrooms potentially mislabelled as slippery jack mushrooms (Moor et al., 2002)
  • domestic pig meat in wild boar products (Conyers et al., 2012)

From the López-Calleja study on mozzarella, one of the gels looked like this:

The PCR was run to detect cow's milk in buffalo cheese. Lane 1 corresponds to 100% cow's milk (it is a very bright band), lane 2 is 10% cow's milk, ranging down to lane 6 which has 0.1% cow's milk (a very faint band), and lane 7 is the pure buffalo cheese which shows no band. Therefore, this assay could be useful to rule out contamination with cow's milk.

Real-time PCR

Running gels is a somewhat old-fashioned way of doing things, and there are better ways to make use of PCR technologies on a larger scale. Real-time PCR is the technique now routinely done to detect food fraud. This is a variant of PCR, which (as the name suggests) allows one to quickly see which PCR products are being produced, in what quantity, and there is no need to run a gel.

For example, real-time PCR has been used to detect:

  • horse and donkey DNA in otherwise-labelled meat products (Chisholm et al., 2005)
  • pork adulteration in commercial beef burgers (Ali et al., 2011)
  • Atlantic cod, Atlantic salmon, and European plaice in fish products (Hird et al., 2012)
  • honey containing pollen from a specific region (Laube et al., 2010)

An example of what the read-out from the real-time PCR is given below. This example is from the Ali study on beef burger adulteration. The letter A was 100% adulterated (i.e. contained 100% pork instead of beef), letter B contained 10% pork, and so-on to E which contained 0.01% pork. F had no pork. The more pork contamination there was, the sooner on the plot (in PCR cycles) the contaminant reached detectable levels:

About the sequence

As you will see from reading about these techniques, it is not so much the sequence itself which is important - it is fragment size or other properties of the region analysed by PCR that is most practically useful. Sometimes the PCR product may be sequenced for comparison purposes, although I do not believe this is done as a routine screening for food fraud.

Keep in mind that PCR is just one of a number of genetic techniques used in food safety. For example, DNA barcoding and SNPs are also useful techniques that are used in this field. The technology is constantly improving and evolving and no doubt more refined and efficient methods are being developed to detect food fraud.


Whole Genome Sequencing (WGS) Program

Whole genome sequencing (WGS) is a cutting-edge technology that FDA has put to a novel and health-promoting use. FDA is laying the foundation for the use of whole genome sequencing to protect consumers from foodborne illness in countries all over the world.

Introduction

Whole genome sequencing reveals the complete DNA make-up of an organism, enabling us to better understand variations both within and between species. This in turn allows us to differentiate between organisms with a precision that other technologies do not allow. FDA is using this technology to perform basic foodborne pathogen identification during foodborne illness outbreaks and applying it in novel ways that have the potential to help reduce foodborne illnesses and deaths over the long term both in the U.S and abroad.

The most basic application of this technology to food safety is using it to identify pathogens isolated from food or environmental samples. These can then be compared to clinical isolates from patients. If the pathogens found in the food or food production environment match the pathogens from the sick patients, a reliable link between the two can be made, which helps define the scope of a foodborne illness outbreak. This type of testing has traditionally been done using methods such as PFGE, but there are some strains of Salmonella spp. that PFGE is unable to differentiate. Whole genome sequencing performs the same function as PFGE but has the power to differentiate virtually all strains of foodborne pathogens, no matter what the species. Its ability to differentiate between even closely related organisms allows outbreaks to be detected with fewer clinical cases and provides the opportunity to stop outbreaks sooner and avoid additional illnesses.

However the most promising and far reaching public health benefit may come from pairing a foodborne pathogen’s genomic information with its geographic location and applying the principles of evolutionary biology to determine the relatedness of the pathogens. Why? Because, the genomic information of a species of foodborne pathogen found in one geographic area is different than the genomic information of the same species of pathogen found in another area. Knowing the geographic areas that pathogens are typically associated with can be a powerful tool in tracking down the root source of contamination for a food product, especially multi-ingredient food products whose ingredients come from different states or countries. The faster public health officials can identify the source of contamination, the faster the harmful ingredient can be removed from the food supply and the more illnesses and deaths that can be averted.

To realize this goal FDA is spearheading an international effort to build a network of laboratories that can sequence the genomes of foodborne pathogens and then upload the genomic sequence of the pathogen and the geographic location from which the pathogen was gathered into a publicly accessible database. As the size of the database grows, so will its strength as a tool to help focus and speed investigations into the root cause of illnesses.

FDA’s foods program has been utilizing whole genome sequencing since 2008.

GenomeTrakr: Using Genomics to Identify Food Contamination

The FDA Foods Whole Genome Sequencing Staff is coordinating efforts by public health officials to sequence pathogens collected from foodborne outbreaks, contaminated food products, and environmental sources. The genome sequences are archived in an open-access genomic reference database called GenomeTrakr, that can be used: to find the contamination sources of current and future outbreaks to better understand the environmental conditions associated with the contamination of agricultural products and to help develop new rapid methods and culture independent tests.

How FDA Uses Whole Genome Sequencing for Regulatory Purposes

Genomic data from foodborne pathogens, by itself and in combination with other information, is a robust resource that can help public health officials identify and understand the source of foodborne illness outbreaks. It can be used: to determine which illnesses are part of an outbreak and which are not to determine which ingredient in a multi-ingredient food is responsible for an outbreak to identify geographic regions from which a contaminated ingredient may have originated to differentiate sources of contamination, even within the same outbreak to link illnesses to a processing facility even before the food product vector has been identified to link small numbers of illnesses that otherwise might not have been identified as common outbreak and to identify unlikely routes of contamination.

Proactive Applications of Whole Genome Sequencing Technology

Although public health officials sequence foodborne pathogens after a foodborne illness outbreak or event has occurred, that isn’t the only time they are sequenced and the genomic information sequencing provides can be used for more than just determining the scope of outbreaks and speeding traceback investigations. It can be used: as an industry tool for monitoring ingredient supplies, the effectiveness of preventive and sanitary controls, and to develop new rapid method and culture independent tests to determine the persistence of pathogens in the environment to monitor emerging pathogens and as a possible indicator of antimicrobial resistance.


There is a whole new universe, waiting to be explored! Welcome to The DNA Universe Blog!

On 20th July, 1969, our world changed when humans walked on the surface of the moon for the first time. This pioneering achievement by Neil A. Armstrong, Buzz Aldrin, Michael Collins and all the engineers and teams of the Apollo 11 mission broadened our reality.

In 1977, Frederick Sanger and his colleagues Nicklen and Coulson introduced the chain-terminator method or dideoxy sequencing or simply Sanger sequencing as we know it. Similar to the moon landing, Sanger sequencing changed the world of biology and dominate the sequencing world for the next 30 years.

Just like Armstrong, Aldrin and Collins stood on the shoulders of giants such as Hans Lippershey and Galileo Galilei who invented the telescope (in 1608/1609), or the Russian cosmonaut Yuri Gagarin who was the first human in space (12th April 1961), Sanger and his colleagues also stood on the shoulders of giants!

Francis Crick, James Watson, Rosalind Franklin and Maurice Wilkins introduced the world to the double helical structure of DNA in 1953.

Robert Holley and colleagues were the first to sequence yeast transfer RNA (tRNA) using RNAses with base specificity in 1965.

Walter Fiers read the first ever DNA sequence of a whole gene – coding for a MS2 virus coating protein – in 1972.


Genetic Genealogy Cheat Sheet

This cheat sheet outlines (in plain English) how you can get started using genealogical DNA testing to unpuzzle your own ancestry questions with at-a-glance charts, tips and resources.

Usually, you’ll register for a site, upload your raw DNA data (the numbers and letters assigned to your genomic variants and their positions on your chromosomes) and perform a variety of analyses. For example, the only way to compare raw DNA data from one company’s test to raw data from another company’s test is to have both sets of data uploaded to the same third-party tool.


Environmental DNA (eDNA)

Environmental DNA (eDNA) is organismal DNA that can be found in the environment. Environmental DNA originates from cellular material shed by organisms (via skin, excrement, etc.) into aquatic or terrestrial environments that can be sampled and monitored using new molecular methods. Such methodology is important for the early detection of invasive species as well as the detection of rare and cryptic species.

What is Environmental DNA?

Environmental DNA ( eDNA ) is used to identify species in water bodies.

DNA, short for deoxyribonucleic acid, is the hereditary material in organisms that contains the biological instructions for building and maintaining them. The chemical structure of DNA is the same for all organisms, but differences exist in the order of the DNA building blocks, known as base pairs. Unique sequences of base pairs, particularly repeating patterns, provide a means to identify species, populations, and even individuals.

Environmental DNA (eDNA) is nuclear or mitochondrial DNA that is released from an organism into the environment. Sources of eDNA include secreted feces, mucous, and gametes shed skin and hair and carcasses. eDNA can be detected in cellular or extracellular (dissolved DNA) form.

In aquatic environments, eDNA is diluted and distributed by currents and other hydrological processes (fig. 1), but it only lasts about 7–21 days, depending on environmental conditions (Dejean and others, 2011). Exposure to UVB radiation, acidity, heat, and endo- and exonucleases can degrade eDNA.

Use of eDNA for Inventory and Monitoring

Improved Detection of Native Species

Protocols using eDNA may allow for rapid, cost-effective, and standardized collection of data about species distribution and relative abundance. For small, rare, secretive, and other species that are difficult to detect, eDNA provides an attractive alternative for aquatic inventory and monitoring programs. Increasing evidence demonstrates improved species detection and catch-per-unit effort compared with electrofishing, snorkeling, and other current field methods. Thus, detection of species using eDNA may improve biodiversity assessments and provide information about status, distribution, and habitat requirements for lesser-known species.

Early Detection of Invasive Species

eDNA may also be an effective tool for early detection of aquatic invasive species. Application of eDNA methods for invasive species monitoring may include periodically collecting water samples and screening them for several invasive species at once. Boat-ballast water, a source of introduction for many invasive species including mollusks, also could be sampled. Some intensive eradication programs for invasive species fail when a few surviving individuals recolonize the ecosystem. eDNA methods may provide a means of confirming eradication of all invaders.


Making a meal of DNA in the seafloor

Credit: Pixabay/CC0 Public Domain

While best known as the code for genetic information, DNA is also a nutrient for specialized microbes. An international team of researchers led by Kenneth Wasmund and Alexander Loy from the University of Vienna has discovered several bacteria in sediment samples from the Atlantic Ocean that use DNA as a food source. One bacterium newly named by the team in fact is a true expert in degrading DNA. The study is now published in Nature Microbiology.

DNA is an abundant and nutritious food source for microbes

The diet of microbes is vast: They are able to use different molecules as nutrients, including biomolecules such as proteins and lipids of dead and decaying organisms. This includes so-called extracellular DNA molecules that are not or no longer present in intact cells.

"From the bacteria's perspective, DNA is particularly nutritious," says Kenneth Wasmund, a microbiologist at the Center for Microbiology and Environmental Systems Science (CMESS) at the University of Vienna and lead author of the study. "It's essentially a fertilizer. After all, it is a chain of millions of pieces of sugar and phosphorus- and nitrogen-containing bases." Extracellular DNA is common in the environment because when any organism dies, its contents, including DNA, are released into the environment. The microbes that degrade such abundant biomolecules are critical for global biogeochemical cycles as they recycle organic material settling from ocean waters, thereby also influencing how much carbon ultimately remains in the ocean floor. Yet, not all microbes are capable of using DNA as a nutrient.

Marine sediments are a massive habitat for undescribed microbes

The muddy sediments of the sea floor are a massive global habitat for these ecologically important microorganisms after all, our oceans cover more than 70 percent of the earth's surface. Thousands of microbial species live here, most of which are still largely unknown. "Our study identifies some of these microbial players and reveals their lifestyles. At the same time, it tells us something about what happens to the vast amounts of DNA that are constantly released into the environment but do not accumulate anywhere and, accordingly, are obviously somehow being recycled," Kenneth Wasmund explains.

Previous research has shown that microorganisms grown in the laboratory might use DNA as an energy source. "Our research has now focused on microbes that actually live and actively function in the seafloor, while using DNA as a food source," he adds.

Deciphering bacteria that use DNA for food by functional microbiome analyzes

To this end, colleagues from the University of Calgary in Canada collected samples from the seafloor in the Baffin Bay, a marginal sea of the Atlantic Ocean between Greenland and Canada. To identify and characterize DNA-foraging microbes in these samples, the research team used an array of experimental, analytical, and bioinformatic methods. "In this collaboration of all four divisions at CMESS, we made full use of the excellent research infrastructure and unleashed the full expertise for functional microbiome analyzes that is present at our Center," says Alexander Loy, head of the research group at the University of Vienna.

In laboratory incubations, the researchers fed purified DNA that was isotopically-labeled with heavy carbon atoms (13C) to the sediment bacteria. Using stable isotope probing, including a specific isotope imaging technique, they were then able to track the heavy carbon and as a result could see which bacteria degraded the labeled DNA. In addition, the scientists reconstructed the genetic information present in the cells, i.e. the genomes, of the DNA-eating microorganisms to learn about their functional potential and distribution in the world's oceans.

Novel DNA-eating bacteria in the seafloor

The metagenomic analysis showed that the bacteria were equipped with DNA-degrading enzymes that enable them to chop-up DNA into small pieces to help them take it up and consume it. One bacterial species stood out as it had a particularly sophisticated set of tools for degrading DNA. Their appetite for DNA, also called nucleic acid, is now borne in their name: The research team named them Izemoplasma acidinucleici.


Is there any websites that provide the DNA sequences of food samples? - Biology

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DNA Evidence Basics: Types of Samples Suitable for DNA Testing

This is an archive page that is no longer being updated. It may contain outdated information and links may no longer function as originally intended.

On this page find basic information on the following types of samples suitable for DNA testing:

Questioned or Unknown Samples

Questioned or unknown samples collected from the crime scene can be any biological sample including: liquid blood or bloodstains, liquid saliva or saliva stains, and liquid semen or dried semen stains (including from vasectomized males) deposited on virtually any surface genital/vaginal/cervical samples collected on swabs or gauze, or as aspirates rectal/anal swabs penile swabs pieces of tissue/skin fingernails plucked and shed hairs (e.g., head, pubic, body) skin cells on drinking vessels, clothing (e.g., neck collars, waistbands, hat linings) slides containing tissue, semen, etc. and liquid urine.

Samples From Unidentified Bodies

Samples collected from unidentified bodies can include: blood, buccal swabs, hairs, bone, teeth, fingernails, tissues from internal organs (including brain), muscle, and skin.

Reference Samples From Known Individuals

The most common reference samples collected from known individuals are blood, oral/buccal swabs, and/or plucked hairs (e.g., head, pubic).

Samples to Use When No Conventional Reference Samples Are Available

Other samples that may be considered when individuals are unavailable or are reluctant to provide samples include clothing where biological fluids may be deposited (e.g., women's panty crotches or blood-, saliva-, or semen-stained items) and other clothing in close contact with the body where skin cells may have rubbed off (e.g., collars, waistbands, hats), bedding (with vaginal/semen stains or rubbed off skin cells), fingernail clippings, cigarette butts, toothbrushes, hairs in razors and hairbrushes, discarded facial tissues or handkerchiefs with nasal secretions, condoms, gum, feminine products, pathology paraffin blocks or slides from previous surgery or from autopsy, and teeth.

Reference Samples From Individuals Who Have Been Transfused

If an individual has received transfusions shortly before the collection of a blood sample (e.g., homicide victim), the DNA test results may indicate the presence of DNA from two or more sources. Generally the predominant DNA types reflect the types from the individual. However, other sources of reference samples for individuals who have received transfusions may need to be collected. These would include: blood-stained clothing or other material (bedding, etc.) and oral, vaginal, and other swabs in addition to the items listed above.

Use of Samples From Relatives for Testing

Because a child inherits half of its DNA from each parent, it is possible to use reference samples collected from close relatives (e.g., biological father, mother, and/or full siblings or the individual's spouse and their children) to identify or confirm the identity of bodies that have not been identified through other means. It is also possible to use reference samples collected from close relatives for comparison to crime scene samples, for example, in missing body cases where a bloodstain or tissue sample from a possible crime scene can be tested to demonstrate a biological relationship to known individuals.

Determination of Paternity or Maternity of a Child or Fetus

Aborted fetal tissue can be analyzed for determining paternity, for example, in sexual assault and/or incest cases where conception occurred. Paternity and/or maternity of a child can be confirmed using blood or other samples listed above from the child and the alleged parent(s).


Nutrition and Fitness

10. Genopalate

Price: $89 - $129
Type: Nutrition
Category: Health and Wellness

“Healthy eating, personalized just for you. Discover your ideal intake of carbohydrates, protein, fats, vitamin and minerals. Get a comprehensive list of the 85+ foods that have a nutrition profile that matches best with your genetic-based nutrition recommendations.”

Genopalate analyzes your DNA for nutrition information, so you will know which specific foods are best metabolized and processed by your body. They analyze 104 SNPs to give you a Genopalate Report that includes your ideal intake of certain nutrients. You’ll also get information on genetic variants that influence the foods you eat. You’ll receive a list of 80+ foods chosen specifically for you based on your unique genetic profile. For an additional fee, you can purchase personalized menus based on your genetic information. These can assist you in eating the right kind of foods based on your genes!

11. Athletigen

Price: Free - $79
Type: Nutrition, Fitness, and Recovery
Category: Health and Wellness

“You know about your past. Now, take control of your future. Nutrition, performance, and recovery markers from your DNA are analyzed to determine which part of the world these genotypes most frequently occur.”

After you upload your raw DNA data for free, Athletigen analyzes your overall health and wellness by looking at how your DNA influences your response to nutrients, performance abilities, and recovery. They have also partnered with the world premier training center, ALTIS, to provide personalized fitness reports for an additional fee. Among the different reports that can be purchased for an additional cost, the ALTIS Sports Performance Report is 35 pages of over 50 markers and 22 traits analyzed specifically for you.

12. Vitagene

Price: $29- $269
Type: Nutrition, Fitness, Skin, and Supplements
Category: Health and Wellness

“Go beyond genealogy. Upload your raw DNA and discover diet, fitness & vitamin traits + recipes plans designed for you”

Vitagene gives you diet, supplement, skin, and fitness reports personalized from your DNA. These reports help you understand and improve your overall health and wellness. In addition to the reports, Vitagene takes orders for personalized supplement packages based on your genetic information.

13. DNAFit

Price: $49 –$89
Type: Fitness
Category: Food and nutrition, Fitness

“Let’s talk about you — Our groundbreaking DNA test will change the way you think about fitness and nutrition forever.”

DNAFit focuses on fitness and diet. The genetic traits covered by DNAFit include antioxidant needs, detoxification ability, endurance performance, power, injury risk, recovery from exercise, and more.


Frozen Zoo®

Our Frozen Zoo ® is the largest and most diverse collection of its kind in the world. It contains over 10,000 living cell cultures, oocytes, sperm, and embryos representing nearly 1,000 taxa, including one extinct species, the po&rsquoouli. Located at the Beckman Center for Conservation Research, the collection is also duplicated for safekeeping at a second site. The irreplaceable living cell lines, gametes, and embryos stored in the Frozen Zoo ® provide an invaluable resource for conservation, assisted reproduction, evolutionary biology, and wildlife medicine.

Germplasm stored in the Frozen Zoo ® has the potential to produce offspring when used for in vitro oocyte maturation and fertilization, artificial insemination, and embryo transfer. Successful artificial insemination of cryopreserved sperm has produced chicks of several pheasant species, and frozen cat oocytes have been matured and fertilized in vitro to form advanced stage embryos. Using methods developed in the domestic cat model, thawed cheetah sperm has fertilized an in vitro matured cheetah oocyte, which then developed into an embryo. With intracytoplasmic sperm injection, southern white rhino oocytes were fertilized with sperm frozen for 20 years.

Currently, we are using the Frozen Zoo ® to develop a bank of reference barcode samples for the identification of illegal primate and duiker specimens associated with the bushmeat trade. To help guide reintroduction efforts for the critically endangered Przewalski&rsquos horse, our scientists have partnered with others to compare the genetic make-up of samples in the Frozen Zoo ® with ancient DNA samples extracted from museum skins in the Russian Academy of Sciences. Whole genome sequencing projects for African elephants, two-toed sloths, and gorillas have all benefitted from the Frozen Zoo ® . An exciting initiative, Genome 10K, is underway to sequence the genomes of 10,000 species in order to provide a new framework for biological inquiry. This worldwide effort will facilitate advances in our understanding of the biology of endangered species that will directly aid in their conservation and management in the wild.

The Frozen Zoo ® constitutes a crucial resource for facilitating advances in genetic and reproductive technologies for population sustainability. In a new collaboration with The Scripps Research Institute, our Reproductive Sciences and Conservation Genetics teams are using the resources of the Frozen Zoo ® to study the potential for emerging stem cell technologies to rescue the northern white rhino from the brink of extinction. Our vision for the future is to develop an international network of cryobanks under the umbrella of a Global Wildlife Biobank that is dedicated to sharing resources and expertise and growing a worldwide legacy of irreplaceable reproductive and genetic material that can be used in support of species conservation.


DNA tests can’t tell you your race

Many people turn to companies like 23andMe to learn about ancestry and ethnicity. But the genetic connection is far more complicated than the industry lets on.

A Spanish-American family photographed in New Mexico in 1940. Today, they'd be categorized as Latinx, even if their origins are more complex. Russell Lee/Farm Security Administration/Office of War

It’s always a mess when Latinx folks take DNA tests. Things go alright, until we get to the “ancestry” portion, which some commercial genetic tests label as “ethnicity.”

People who identify as Latinx claim ancestry from all over: indigenous Americans, Spanish colonists, enslaved Africans, Middle Eastern people, miscellaneous Europeans, and even Asians.

This can lead to unexpected DNA results. My grandfather is Mexican, but fair-haired and blue-eyed (we sometimes call people who look like him bolillo, which means “white bread”). When he got his report back from FamilyTreeDNA, he found out he had more North American ancestry than expected. Abuelo made some weird comments—but my friend’s brother’s reaction was much worse. Also Mexican, he came into the living room with his tests results printed out. “I found I’m 3 percent black,” he said. “What’s up my n*****s?”

Thankfully, his family quickly corrected him: “You just can’t say that word!” But to correct him more fully, they would need to let him know that a DNA test, no matter how sophisticated, can’t tell him what his race is.

Abuelo and my friend’s brother aren’t alone in their confusion. In the past few years at-home genetic testing has grown into a billion-dollar industry since 2013, more than 26 million people have sent in their DNA for analysis. And while companies like 23&Me, AncestryDNA, and MyHeritage claim to be able to tell your “ethnicity”—a word they know many people will read as a synonym for “race”—none of them explicitly offer to tell consumers their racial make-up. There’s one simple reason for that: The science just doesn’t exist.

To understand this, let’s go back to my friend’s brother. He thought the test told him he was “3 percent black,” when in fact it reported that he had a 3 percent chance of having genetic ancestry from some part of the African continent.

How’s that different than being “3 percent black”? First off, that percentage is being interpreted incorrectly. A lot of people read their DNA tests like a pie chart: You’re 25 percent this or 50 percent that. But that’s not at all what the statistics represent.

“They are fractions, estimates. It’s saying that your genome has a certain percent estimate of representing a certain area,” says Marcus Feldman, a professor of biological sciences at Stanford University and director of the Morrison Institute for Population and Resource Studies.

Feldman explains that when it comes to people’s roots, the tests are saying something more like: We’re 30 percent confident that your DNA indicates ancestry from Okinawa, Japan. That’s not the same thing as saying someone is 30 percent Okinawan.

The vast majority of human DNA—we’re talking 99.9 percent—is entirely identical between individuals. So when the code diverges between two people, that’s interesting to scientists. A DNA ancestry test scans the entirety of your genome looking for single-letter differences. Statistical experts like Feldman have figured out that people from the same continent, on average, tend to have certain variations in the same regions of DNA. Still, it’s impossible to say that one tiny nuance comes from a specific place analysts can only note when someone’s differences overlap a lot with a general geographic group.

“You can’t take your DNA and chop it up and say, ‘This bit came from here, and that bit came from there,’ ” Feldman says, laughing.

Feldman knows what he’s talking about: He was a part of the Human Genome Diversity Project, the first research group that sought out connections between genetics and geographic ancestry. Starting in the 1990s, collaborators began using blood samples collected from around the world to try to understand human migration and evolution. The result was the first-ever “map” detailing commonalities in the DNA of people from different regions. It was a monumental achievement: The Project’s results are still the baseline for most consumer tests on the market today.

Back to Feldman’s point about divvying up DNA … you might think your ancestry works sort of like inheriting genes from your parents—an even 50/50 split. But that’s not the case when you go back another generation, as DNA reshuffles and reorganizes with every new transfer. So even if your mom gave you 50 percent of her own genes, doesn’t mean you got an even portion of, say, her Pakistani parent’s. In fact, if you dig far enough, it’s possible you’ll find a direct ancestor that you have no genes in common with.

This means that you and your sibling can have significantly different ancestry results, given you’ve each inherited different portions of your parents’ DNA (unless you’re identical twins).

An African American family photographed in the early 1900s. Edith Wilson/R. K. Mellon Family Foundation

That brings us to another important detail: the fact that ancestry and physical appearance (or phenotypic traits) don’t directly overlap. Characteristics like skin color, hair texture, and eye shape are controlled by thousands of different genes—separate from the ones scientists look at when composing an ancestry profile. As a result, someone with a high estimate of West African ancestry might not look or even identify as black. Similarly, an individual whose tests come back with a very low estimate of West African ancestry might actually be black.

That’s why geneticists haven’t devised a test that can conclusively determine a person’s race. And in a way, it’s impossible. Race is about how we identify and are identified it’s more than a question of appearance—it’s a question of culture, history, geography, and family. It can’t be boiled down to genetics and percentages.

“It’s fundamentally flawed to think that a genetic test can figure out race,” says Sarah Tishkoff, a professor of genetics and biology at the University of Pennsylvania. “The biggest issue is distinguishing between ancestry and race. Race is a socially constructed concept. How someone self-identifies in terms of their ethnicity or race may be different than what their genetic ancestry tells us.”

In fact, our concept of race has such little biological grounding that the Human Genome Diversity Project has opted to avoid using the word entirely.

“In our first papers on this, we never used the word ‘race.’ We used the term ‘ancestry,’ ” Feldman says. “Where is the continental ancestry? I still maintain that this is the only way to introduce anything biological or genetic into that discussion.”

Think about it in terms of science and history. European colonizers invented the concept of race 500 years before the double helix was discovered. Many of their terms for describing human difference, based on traits like skin color and facial features, are still used in our censuses and societies today. (For instance, our idea that a person can be “one-fourth” something comes from the logic Europeans used to figure out which mixed-race people were “black enough” to enslave.) This category-forming was not a scientific process—it wasn’t Mendel in a greenhouse with his peas. It was backed by men with giant armies, whose objectives were mass enslavement, conquest, and subjugation.

“I think in that period when Europe was dominant, [racial terms] were a way of classifying levels of inferiority,” Feldman says, speaking of the birth of white supremacy. “It was a validation of colonialism.”

This is what some people mean when they say race isn’t real: It’s a social concept created to empower Europeans, as much as it was created to describe differences between people. That’s why modern historians and geneticists worry about how people are trying to use DNA to define race .

“We think that when people use racial classifications when talking about genetic data, it may reify the wrong idea that there’s a biological basis to racial classification,” Tiskoff says.

In an ironic twist, however, race—and racism—have affected how we understand ancestry. DNA tests like 23andMe pack a strong Eurocentric bias because they’re based on genetic research that’s largely from one continent. In fact, the original samples analyzed by the Human Genome Diversity Project didn’t include any samples from North America.

While efforts have been made to produce more geographically representative samples, at-home DNA tests still give far more detailed answers about European ancestry than most other parts of the world. My grandpa’s tests, for instance, included incredible granular detail on his profile from the Iberian peninsula (it went so far as to suss Sephardic Jews from other Spaniards). But his American ancestry just said “North America” (a category that lumps Inuits together with Aztecs).

All this leaves us with the question of how we should talk about race as genetic analysis becomes more commercialized and common. The results, no matter how personal, can have serious social ramifications. There are websites that offer advice to white people on using DNA testing to apply for “minority status” in college admission. That cynical use of biological data should make us deeply uncomfortable—and it should make us think further about the information that helps us define our own identities.

The history you glean from a DNA test comes from context that biology can’t provide. It’s your choice to seek out that context, draw the lines to ancestors and colonial legacies, and determine who you are today.