In sexual reproduction in mammals the DNA in the sperm and egg joins up so that homologous sequences are aligned with each other. This is followed by exchange of genetic information to form a new recombined chromosome which is passed on to the offspring.  Cell division then takes place and the chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. The double-stranded structure of DNA provides a simple mechanism for DNA replication. In this process the two strands are separated and then each strand’s complementary DNA sequence is recreated by an enzyme.
When a sample of biological material contains DNA from more than one person, this can result in a “mixed DNA profile”. In such profiles, there may be a reduced amount of useful information regarding whether or not a specific person could have contributed to this sample. This could be because the contributors may share one or more DNA alleles, resulting in the masking of the DNA of one person by that of the other.
Home DNA testing has gone from a niche pursuit to a simple way to map out your family tree. A DNA test can be used to determine paternity and research ancestry or familial origin. And over the past few years, they've become quite affordable, with a wide range of companies selling DNA test kits -- from trailblazers such as Ancestry and 23andMe to upstarts that include LivingDNA. 

While DNA contains material common to all humans, some portions are unique to each individual. These portions, or regions, contain two genetic types (alleles) that are inherited from the person’s mother and father. A person’s DNA profile is made by investigating a number of these regions. In a paternity test, for example, the mother’s DNA profile is compared with the child’s to find which half was passed on by the mother. The other half of the child’s DNA is then compared with the alleged father’s DNA profile. If they don’t match, the ‘father’ is excluded, which means he isn’t the father of that child. If the DNA profiles match, the ‘father’ is not excluded - which means there is a high probability (more than 99 per cent) that he is the father. DNA tests such as this can’t offer 100 per cent proof.

Men have an X and a Y (chromosome) that are paired together. Women don’t have the Y, they just have two X’s. A child’s genes come from a mix up and recombining of the two parents. So a girl child will still end up with two X’s but some bits of them will come from the father’s X and some from the mother’s. A boy child on the other hand may have some bits of X from both mother and father, but his Y will have just come purely from his father – virtually unchanged. That makes Y-DNA such an exciting possibility for genealogy where you want to follow the paternal (surname) line. You could expect that Y-DNA will therefore pass virtually unchanged from father to son through the generations, meaning that the Y-DNA of a man’s g-g-g-g-grandfather will look very much like that of his own Y-DNA – with some little changes.
Living DNA offers the best biogeographical ancestry analysis on the market for people with British ancestry and they are the only company to offer regional breakdowns. With the inclusion of Y-DNA and mtDNA haplogroup information, this is a good all-round test for someone who wants an overview of their genetic ancestry. The test cannot currently be used for genealogical matching, though an autosomal matching service is promised for the future. As a late entrant to the market, Living DNA will start with a smaller database though the test is more likely to appeal to people in the UK, especially those who feel safer keeping their DNA data in Europe.

Living DNA supports 80 geographical ancestry regions, 21 of which are located within Britain and Ireland alone, making it a great DNA test for people wanting to delve deep into their British heritage. Of course, it also covers 60 regions outside of the British Isles, and is expanding its efforts to bring the same level of detail to other world regions.
It is very important that you take the time to read the privacy policy, terms and conditions and consent forms associated with any DNA test you take or any site you choose to upload your data to. While FTDNA has a proven track record of protecting the privacy of its users, there have been serious concerns over how AncestryDNA and 23andMe have used data in the past, as well as how they may use or sell your data in the future. Please read this article from Roberta Estes for more information on this issue. MyHeritage states that their consent form (that would allow sharing or selling of your results in aggregated data) is optional.  You can read more about that on The Legal Genealogist, who compliments MyHeritage DNA on their policy and openness.
Our Ancestry Service helps you understand who you are, where your DNA comes from and your family story. We analyse, compile and distill your DNA information into reports on your Ancestry Composition, Ancestry Detail Reports, Maternal & Paternal Haplogroups, Neanderthal Ancestry, Your DNA Family and provide a DNA Relatives tool to enable you to connect with relatives who share similar DNA.

For better ancestry and medical insights, you should encourage family members, especially parents and grandparents, to take a DNA test as well. If your family is from a specific geographical location for generations, your samples could potentially improve the service's reference panel, in turn improving results for everyone. If you’re female and take a test from 23andMe or LivingDNA, you can view paternal haplogroup information, and you get more information when one of your male family members takes a test as well.
Whole genome sequencing is the most accurate representation of your DNA that you can buy, as it provides you with the details of every single base in your DNA (more than 5 billion). This is unsurprisingly much more expensive than DNA profiling, and isn’t necessary if you are looking for a profile for identification purposes. However, if you’d like to know more about DNA sequencing, we’ve listed the companies that can sell you your sequence.
the beauty of a y-DNA test is that it tracks the paternal y-chromosome…..yes, even indicating a surname change but not when the surname changed [does not match known male descendants]. In all DNA testing, it really helps to have researched about 5 generations back on all lineages……that way you can find common surnames in the autosomal tests. The y-DNA tests go back for centuries…..and the autosomal testing really only goes back about 5 generations…….
Specific tests for your father’s family include ‘Y-DNA’ tests which focus on the ‘Y chromosomes’ in your cells’ nuclei, passed down from father to son. Specific tests for your mother’s family include ‘mtDNA’ tests which report on a subset of DNA found in the ‘mitochondria’ (your cells’ energy factories), passed down from mother to son or to daughter.

Early and active treatment of FH can substantially reduce the risk for heart disease. FH treatment focuses on lowering LDL cholesterol levels, and FH is usually treated with cholesterol-lowering medications. Lifestyle modifications, including diet, exercise, and weight control can help lower LDL cholesterol levels. But these changes are generally not enough to effectively manage the condition. In extreme cases of FH, LDL-apheresis, a procedure that filters cholesterol out of the blood, can be used when other treatments have failed.
Although FamilyTreeDNA is the only DNA testing company openly working with law enforcement, other DNA companies don’t necessarily keep your DNA information private. Many direct-to-consumer DNA testing companies sell your data to third parties. For example, 23andMe shares customer data with pharmaceutical giant GlaxoSmithKline, which uses the information to develop medical treatments. In this case, you can opt out of having your DNA information used for research, and the data is shared only in aggregate.

Once your genetic information is out there, it’s difficult to undo. Also, once you know something about yourself, it’s impossible to forget. Revelations such as having different parents than you expected or finding unknown half-siblings are difficult to process at any age, but it’s particularly troubling for kids. However, you can always simply opt out of family matching features.
In the case of a great-grandchild, or a great-great-grandchild, something even stranger can happen.  Remember that a child will get half of their mother’s DNA, but there is never ever guarantee which 50%.  The way it is chosen is fairly random, as far as scientists know.  Take the example of the 100% Eastern European person.  Their great-grandchild will inherit 50% of their DNA from their part-Eastern European parent, but there is a good chance that they won’t inherit all of the Eastern European DNA that they could potentially inherit.  It’s possible for a person to share NO DNA with a great-great grandparent, even though there is a verified genealogical relationship.
Most direct-to-consumer DNA test companies warn that the tests may reveal things you wish you didn’t know about your family. For example, you could find out that one of the people who raised you isn’t your biological parent or that there’s an entire branch of your family you didn’t know about. There isn’t a way to prepare for a shock like that, but you can opt out of a company’s family-matching services if you’d rather not know.
23andMe is a bit different in that many people have tested with their company for the health results and are not necessarily interested in genealogy or matching with relatives, even if they opted into this feature. That doesn’t mean you won’t get a good response when reaching out, but it may be less common than with the other testing companies. Recently 23andMe has been placing more focus on genealogical testing, however, so this is may be shifting.

Hi Mark, Thank you for such an informative and clearly stated article. I am American Jewish and have done several of the tests. I’m now submitting a question for a close friend. He is Burmese and would very much like to test. His biggest interest is ancestral origins. Would he be best off doing a Ydna test or could he find sufficient information in an autosomal test? I assume the Y test would be with Familytree. If so, should he also do an autosomal test with Familytree, or with Ancestry or MyHeritage? Thank you so much!
As well as showing you which ethnic groups you’ve inherited your DNA from, autosomal DNA tests can also be used to find living relatives and build your family tree. Many people attempting to build their family tree will often make breakthroughs in their research when they combine a DNA genealogy test (such as an ethnicity test) with traditional genealogical techniques.
It’s easy to do these tests; it’s usually just a case of collecting your own samples at home, filling in short, basic questionnaires, posting the packages, and then logging on to interactive websites for confidential results (all the kits I tested used outside laboratories). With an array of price ranges and options, from one-off DNA-blitzes to targeting specific health areas, to fitness/wellness tracking, it’s no surprise that these kits are proving to be very big business and the field is primed to get even bigger, with a global market estimated to be worth around £7.7bn by 2022.
When I found out about AncestryDNA, I thought this could be the perfect tool to pinpoint where my family emigrated over the past few hundred years (AncestryDNA can actually go back 1000 years) and give me a focus where to take my search next. When I got the email that my results were ready I felt like a kid on Christmas day. They revealed that I was only 40% British, 25% German and 35% Greek. I’ve now focused my search on these three countries and already discovered ancestors I never knew existed.
Companies differ in terms of which reference populations they use. Some companies will create their own reference populations, while others will use populations identified in published studies. For example, 23andMe produce their own reference populations by sampling their customers (as long as the grandparents of those customers were all born in the same country). They then combine this data with public population data, produced by projects such as the Human Genome Diversity Project.
Looking at your raw DNA file might not give you any useful information unless you’re looking for a specific marker. You can also upload the file into a third-party DNA databases for information or results beyond what’s available from your testing company. This process is not without risks, as your DNA testing company only ensures the security of your personal information in its own environment. Once you download the file, you’re responsible for the file’s security. However, uploading your raw DNA to a third party database isn’t inherently unsafe — just be cautious.
To prepare to take a cheek swab sample, you also have to refrain from eating for about an hour before. Swab kits generally contain more components, including one or two swabs and containers to protect the used swabs from contamination. We found it easiest to organize all the pieces first, to prevent any fumbling with a sample collection swab in hand. Some cheek cell kits put a stabilizing liquid in the sample containers, which required extra caution to prevent spilling.
If you're creeped out by how much information Facebook, Google and Amazon have on you based on your online browsing habits, just remember that these DNA testing services are getting what is effectively your medical history. Make sure of their policies before turning over that valuable data. Also, even if you don't share your DNA with a service, your familial DNA data may be available if a relative shared their genetic material. The privacy issues can get very complex.
AncestryDNA recently updated their service, adding new regions and adjusting their algorithm to make their ethnicity estimates more accurate. You're not alone in being a bit bewildered, since plenty of people have had their results change unexpectedly. As genetic ancestry analysis is a relatively recent science and is improving all the time, your results will become more accurate as more people enter the Ancestry database, allowing them to hone their algorithm accordingly.
In Newman’s view, the genie is out of the bottle with home genetic-testing kits. He says that while the kits could potentially provide data in the future, right now, they lack “clinical utility” – they look at genetic variants that, individually, have a very low chance of predicting specific health risks, as there are too many variables: “It’s like the Opportunity Knocks clap-o-meter, with some people further along the scale, and therefore more likely to get the condition and then people at the other end of the scale, who are unlikely to get it.”

Still, it is fun see a visual and numerical representation of where your ancestors came from (generally speaking) and, although there are those who swear by one company or the other, all of these testing companies do a fairly decent job of giving you a report you can enjoy and use in your research. FTNDA recently updated to the much anticipated MyOrigins 2.0 and MyHeritage DNA just updated to their improved 42 population Ethnicity Estimate and offers a nicely detailed report.

The 100,000 Genomes Project is an NHS initiative, run by Genomics England, and is the largest national genome sequencing project in the world. On entering, patients have their entire genome, of more than 3bn base pairs, sequenced. This is different from commercially available genetic testing kits, such as those from 23andMe, which only look at very small stretches of DNA in a process called genotyping. The hope of the NHS is that having so much genetic information, from so many different people, will allow “groundbreaking discoveries about how diseases work, who could be susceptible to them, how we can treat them, and what treatments might work”.

When I found out about AncestryDNA, I thought this could be the perfect tool to pinpoint where my family emigrated over the past few hundred years (AncestryDNA can actually go back 1000 years) and give me a focus where to take my search next. When I got the email that my results were ready I felt like a kid on Christmas day. They revealed that I was only 40% British, 25% German and 35% Greek. I’ve now focused my search on these three countries and already discovered ancestors I never knew existed.
McCartney says that anxious people often contact her, saying they wished they hadn’t done the tests. “These companies often say that it’s worth it for the helpful advice. But I can give you really good advice right now without seeing a single test result: be active, have lots of social networks, do work you enjoy, try not to smoke or drink too much, don’t be overweight or underweight, eat lots of fresh fruit and vegetables. Nobody needs to get tests done to get that kind of basic lifestyle advice.”
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And that’s where it starts getting interesting, because then we can start comparing that genetic signature to the results from other men who share the same surname but don’t appear on our family tree. If the matches are close, then we can start thinking “is there a common ancestor for these families another generation or two back? Are the families linked in some way?”. Depending on what we already know about either family group, it can help target the paper research to get those families linked, or take us back another generation or two.