Yeah, I've done it. I had mine done at both Ancestry and 23andMe. I can't think of a reason anyone would want my DNA, so I didn't worry about it. If China or Russia got hold it it, it's possible they could create a virus tailored specifically to me and kill me dead, but I can't think of any valid reason either of them would take such a deep interest in me.
Your DNA is different from that of your parents - you got half of it from one, and the other half from the other, and when it combined to make you, it created a unique DNA signature.
When I had mine done, I downloaded the raw DNA files, and I have software here to analyze them. I used that software to combine the files and throw out the doubles where the same SNP was tested, unless one or the other came back as a no-call on that SNP. I used to other file to fill in the blanks there. The resulting file was almost twice the size of either of the originals, with some of the blanks filled in and far more SNPs that one company tested and the other didn't all combined into a single file to make a finer-grained profile for more accurate analysis.
Since those two companies test different SNPs, the results from each differs somewhat from the other. On top of that, they both use different control populations, which make the results even more variable between them. The results are heavily weighted by the control populations they have available to compare your DNA to - they can't find anything they haven't got a control population to compare it against. As time goes on, they are steadily increasing their control population database, but it ain't there yet.
For example, one of them found Nigerian DNA while the other didn't. One found Central Asian where the other didn't. Things like that. When I upload the combined file to third party analysis sites, they find yet other things. One will even compare your DNA to ancient samples from archaeological digs to allow you to track your ancestry through time. For example, my DNA matches a skeleton dug up from a burial at Brattahlid, Greenland, Erik the Red's farmstead. I match 5 or 6 burials from Iceland, from around the time the vikings settled it. Bronze Age Britons are in there, too.
In your specific case, your parent's DNA, particularly your mother's DNA, can help you get past that roadblock you ran into when you were researching your family tree. Depending on the service they used to get tested, it's likely there is a section of the website on their profile that lists DNA relatives. If they were both tested at the same place, then you can tell which relatives are on which side. First cousins have a common grandparent, second cousins a common great grandparent, and so on. You start that search by looking for the appropriate cousin relationship, and then examining their family trees for people leading back to a known grandparent.
Both Ancestry and 23andMe have facilities for creating and comparing family trees on their sites. Ancestry in particular is geared towards finding relatives and researching family trees, as it is run by LDS, and they're real big on bloodlines on account of a religious factor.
I've been tinkering with my own DNA for 4 or 5 years now, so if there is anything you need to know, just ask, and I might have the answer.
ETA: My Dear Old Dad died in 1998, and never had his DNA done. I took my DNA, and one of my sisters' DNA, and have reconstructed dad's DNA file by about 75% or so. I could get it finer, but the rest of my sisters are like you, reluctant to let anyone test their DNA, so what I have of dad's file is likely to be all I'll ever have.
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Your DNA is different from that of your parents - you got half of it from one, and the other half from the other, and when it combined to make you, it created a unique DNA signature.
When I had mine done, I downloaded the raw DNA files, and I have software here to analyze them. I used that software to combine the files and throw out the doubles where the same SNP was tested, unless one or the other came back as a no-call on that SNP. I used to other file to fill in the blanks there. The resulting file was almost twice the size of either of the originals, with some of the blanks filled in and far more SNPs that one company tested and the other didn't all combined into a single file to make a finer-grained profile for more accurate analysis.
Since those two companies test different SNPs, the results from each differs somewhat from the other. On top of that, they both use different control populations, which make the results even more variable between them. The results are heavily weighted by the control populations they have available to compare your DNA to - they can't find anything they haven't got a control population to compare it against. As time goes on, they are steadily increasing their control population database, but it ain't there yet.
For example, one of them found Nigerian DNA while the other didn't. One found Central Asian where the other didn't. Things like that. When I upload the combined file to third party analysis sites, they find yet other things. One will even compare your DNA to ancient samples from archaeological digs to allow you to track your ancestry through time. For example, my DNA matches a skeleton dug up from a burial at Brattahlid, Greenland, Erik the Red's farmstead. I match 5 or 6 burials from Iceland, from around the time the vikings settled it. Bronze Age Britons are in there, too.
In your specific case, your parent's DNA, particularly your mother's DNA, can help you get past that roadblock you ran into when you were researching your family tree. Depending on the service they used to get tested, it's likely there is a section of the website on their profile that lists DNA relatives. If they were both tested at the same place, then you can tell which relatives are on which side. First cousins have a common grandparent, second cousins a common great grandparent, and so on. You start that search by looking for the appropriate cousin relationship, and then examining their family trees for people leading back to a known grandparent.
Both Ancestry and 23andMe have facilities for creating and comparing family trees on their sites. Ancestry in particular is geared towards finding relatives and researching family trees, as it is run by LDS, and they're real big on bloodlines on account of a religious factor.
I've been tinkering with my own DNA for 4 or 5 years now, so if there is anything you need to know, just ask, and I might have the answer.
ETA: My Dear Old Dad died in 1998, and never had his DNA done. I took my DNA, and one of my sisters' DNA, and have reconstructed dad's DNA file by about 75% or so. I could get it finer, but the rest of my sisters are like you, reluctant to let anyone test their DNA, so what I have of dad's file is likely to be all I'll ever have.
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Diogenes was eating bread and lentils for supper. He was seen by the philosopher Aristippus, who lived comfortably by flattering the king.
Said Aristippus, ‘If you would learn to be subservient to the king you would not have to live on lentils.’ Said Diogenes, ‘Learn to live on lentils and you will not have to be subservient to the king.’
Said Aristippus, ‘If you would learn to be subservient to the king you would not have to live on lentils.’ Said Diogenes, ‘Learn to live on lentils and you will not have to be subservient to the king.’