According to a study in the International Journal of Legal Medicine , genetic sequences on the Y chromosome can be amplified through PCR as well, depending on the chromosomal sex of the child. As far as genetic tests go, paternity tests are rather straightforward.
Modern genetic testing techniques, like those used Chowdry's labs, make use of microarray testing. According to the NIH, this is a microchip-based technique which is capable of reading hundreds of pieces of genetic material at once. This is not only capable of establishing parent-child relationships, but also of using genetic similarity to establish more distant and even ancestral familial relationships between people.
While using DNA microarrays would certainly be capable of establishing paternity, according to Chowdry, these techniques would be "overkill. Given the limited variety of blood types, if all the potential fathers have the same or similar blood types, little could be inferred from the test.
While paternity tests can be performed this way, much more accurate tests have since been developed. In the s, scientists began performing the first prenatal genetic tests by gathering samples of amniotic fluid to test for chromosomal abnormalities. 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. The more SNPs we share in common with another person, the more likely we share a similar, and more recent, ancestry. Your ancestry is estimated by comparing your SNP results with a genetic database of people with known ancestries more on this in the next section.
But even with that high level of accuracy, when you process 1 million places in the genome, you might get 1, errors. Those small errors alone can help explain why one twin might have slightly different results from another. This source of error is why the health results you get back from genetic testing companies may show discrepancies too. Errors aside, the genotyping we get from each of the consumer testing companies should be just about identical to one another that is, if the companies are looking at the same set and number of SNPs.
But how companies analyze that raw data varies. Companies like 23andMe, Ancestry. The tests are looking for evidence that you have common ancestors with people in the reference group. But the reference group each company uses can be different. And the reference groups are changing all the time. As STAT news reports , people who used these tests just a few years ago are now finding their results have changed. Yet it also undercuts their marketing, which implies that their tests reveal something fundamental about you.
Another limitation: These reference groups are largely based on people who are self-reporting their ancestry. Prior to this past summer , 23andMe could only match people to just three broad regions in sub-Saharan Africa, which is an enormous area with a lot of geographic and ethnic diversity.
This is where computer programs come in. Autosomal tests can get you quality genetic information going back about four or five generations. Because the Y-DNA and mtDNA tests are more focused on one side of the line, you can get information going back farther, but with less data about family structure.
Which test you take depends entirely on what you're looking for. Don't expect perfect accuracy. They can give you indications, but taking a DNA test won't magically produce a history book of your family's background.
So, there you go. In the guide , we present to you 10 of the more interesting DNA services we've found. Some are better than others, so you should not only take our information into account when spending on a service, but look for reviews and stories posted by those who have used the services to see what their experiences have been.
It's been interesting -- and also disturbing. By combining the DNA tests with Ancestry's research database, my wife and I were able to answer some long-kept mysteries about our family trees. Here's my story about that, as well as in-depth reviews of those three services:. By the way, a spokesperson at Ancestry reached out to me to talk about the data privacy concerns I raised in this article. They wanted to share this statement:. Protecting our customers' privacy is Ancestry's highest priority, and that starts with the basic belief that customers should always maintain ownership and control over their own data.
We will not share customers' personal information with third-parties - including insurers, employers, health providers or external marketers - without their explicit, informed consent. Ancestry will not share any DNA data with law enforcement unless compelled to by valid legal process and will always seek to minimize the impact on our customers' expectations of privacy. I am personally fascinated by Ancestry and the work they're doing, so I hope to be able to bring you more from them over time.
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