The companies do have webpages that explain these limitations, but you have to dig a bit to find them. You could very easily purchase one of these kits without coming across it. Consumer genetic testing is growing explosively. According to the MIT Technology Review , 26 million people or more have taken a genetic ancestry test.
Tech Review also found that in , the number of tests purchased surpassed sales of all previous years combined. As the market grows, consumers need to be aware of what exactly these tests are telling them and even more so when it comes to information about health and wellness. Even though genetic ancestry tests deliver precise percentages about our heritage, the reports are best thought of estimates, based on imperfect data. There are about 3 billion base pairs — the individual letter instructions of our genetic code — that make up the human genome.
When you spit into a tube and send it off to a company like 23andMe, Ancestry. That would be overkill. All humans have about So instead, to speed up the process, the tests look out for the locations on the genome where people commonly vary from one another.
These are spots where you might have the nucleotide the molecule that forms one half of a base pair adenine and I have thymine. In all, these single-letter changes in our DNA can help explain why one person is taller than another, or why one has brown eyes and another green.
Companies can analyze half a million SNPs or more in an ancestry test. When a genetic testing company gets a tube of your saliva in the mail, it first has to extract the DNA from it. They make copies of your DNA, then break those stands up into shorter chunks. The chunks are then fed into a machine called a genotyping array. These arrays kind of — and this is an absolute simplification — work like a coin sorter, but for SNPs. Many SNPs are meaningless when it comes to our health.
But they can be useful starting points for tracing ancestry. He used a version of these methods in his pioneering work tracing the common ancestor of all living humans, a woman referred to as " Mitochondrial Eve " who lived about , years ago.
And researchers still use these methods to track the movements and intermixing of human populations from the deep past to recent history. If a genetic anthropologist has a DNA sample and a very large library of other samples to compare it against, that anthropologist can quickly figure out which groups in the library that DNA is most closely related to, Stoneking said. Researchers can track paternal ancestry by looking at the Y chromosome, which fathers pass to their male children.
Maternal ancestry, similarly, can be found in mitochondrial DNA, which mothers pass to all of their children. The richest and most detailed ancestry information, however, comes from comparing everything else — the 22 non-sex chromosomes — against the massive libraries. It compares it against British; it compares it against West African; it goes through the entire list, and it spits out a probability for [where that piece of DNA came from].
So, if your 23andMe test says you're 29 percent British, it's because 29 percent of the pieces of your DNA were most likely to have come from a group that 23andMe's reference library has labeled "British.
The names for those ancestry groups, Stoneking said, come from a mix of self-reports many people can describe their immediate background pretty well and independent research. One tiny spelling tweak could contribute to making you taller or change the color of your eyes. Another might put you at a higher or lower risk for some disease.
When compared to someone else, the precise spelling of sequences in your DNA can show how closely related you two are. There are many companies that will test DNA — for you and even your cat or dog no fish, gerbils or birds, yet.
But all DNA tests are not created equal. What you learn about your genetic makeup depends on the company you choose and the level of testing it does. There are three main types of tests. In reality, they will miss some as if they were speed-reading and skipped a letter or word now and again. In the image above, zooming in on the gold bars under chromosome 12 shows such testing gaps.
Whole-genome sequencing will not detect large chunks of missing or re-arranged DNA. It also might miss when a section of DNA has been repeated over and over. Companies such as Veritas Genetics offer this testing for people if prescribed by a doctor. DNA contains a lot of letters. Some sequences make proteins.
Could I finally get a clear answer? I had no cultural knowledge of Nigeria; should I now start claiming it as my own? Did the results mean my very distant ancestors were Nigerian, or that my biological father was probably from there?
Why did my features not resemble a typical west African? I felt more confused than ever. While DNA home tests are more popular than ever, people are starting to raise questions about what happens after the results land. Identities that have been cherished by families for generations can be dismantled overnight.
A yshah Blackman, in her 50s, is of Caribbean descent and lives in London. Blackman was encouraged to take the AncestryDNA test as part of the programme, and thrilled to eventually connect with her long-lost sibling, living on the other side of London. But she was shocked by the details of the results; according to the test, Ayshah had no Indian DNA at all.
I began to think that my grandmother had had an affair, that my mother had an affair. For people of African descent , whose individual and collective histories are blurred by the legacies of colonialism, slavery and rape, what they know about their identities is particularly important.
Blackman felt that one of the narratives woven through her family had been broken.
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