Written by Ellen Hinkley
3 February 2017
Source: DNA Testing Choice@DNATestingChce (The UK’s leading news and reviews site for the DNA Test you can buy online) access 2/7/2017
When it comes to DNA testing to explore your genetic heritage, there are three main types of test that you can take: Genetic ancestry tests, genetic predisposition tests and trait tests.
Ancestry tests can report on your ethnic mix and allow you to trace your ancestry back hundreds of thousands of years. There are three main types of genetic ancestry test: Y-DNA tests, mitochondrial DNA (mtDNA) tests and autosomal DNA tests.
Genetic predisposition tests can be used to identify any medical conditions that you might be predisposed to suffer with later in life. Trait tests can report on the physical or psychological attributes you’ve inherited. For example, you may discover that you’re predisposed to anger quickly, and that your short temper is part of your genetic heritage!
If you’d like to explore your DNA heritage with an ancestry test, we’ve listed the companies that provide genetic ancestry testing. If you’re more interested in understanding how your genetic heritage could affect your health, then check out the companies selling genetic predisposition tests such as Veritas Genetics. If you’re wondering about the traits that you’ve inherited, our personality testing listings are a good place to start!
Genetic ancestry tests
Y DNA tests
Y DNA tests analyse the Y chromosome which is passed down from father to son – for this reason, only males can take this type of test. Y DNA tests allow you to trace your paternal line (your father’s father’s father etc.) by revealing your paternal ‘haplogroup’ – a code used to describe the individuals with whom you share a common paternal ancestor. Your paternal haplogroup can be used to reveal the migratory path that your paternal ancestors took after leaving Africa 100,000-200,000 years ago. Some Y DNA tests will also allow you to find living relatives on your paternal line, to help you undertake DNA genealogy. You can find out more about tracing your paternal heritage with a Y DNA test in our article: What is a Y DNA test?
Mitochondrial DNA tests
Mitochondrial DNA testing provides similar information to Y DNA testing, but instead analyses the DNA that you inherit exclusively from your mother. Mitochondrial DNA is passed down from mother to child, regardless of gender, so anyone can take this type of test. Similarly to Y DNA tests, mitochondrial DNA tests will provide you with your maternal haplogroup, allowing you to explore your maternal genetic heritage going back several hundred thousand years. Some mitochondrial DNA tests are also genealogical DNA tests, helping you to find living relatives on your maternal line. You can read more about mitochondrial DNA testing in our article: What is a mitochondrial DNA test?
Autosomal DNA tests
Autosomal DNA testing allows you to explore your more recent genetic heritage (the last five to six generations of your family), by analyzing 22 of the 23 pairs of chromosomes that you inherit from your parents (your autosomes). Because your autosomes recombine shortly after you’re conceived, it’s not possible to identify which autosomal segments you’ve inherited from which parent, so these tests give you a combined view of your genetic heritage from both parents.
Autosomal DNA tests (sometimes known as ethnicity tests) will reveal the ethnic groups who’ve contributed to your DNA, and some tests double as genealogy DNA tests, allowing you to find living relatives with whom you share segments of your autosomal DNA. You can read more about autosomal DNA testing in our article: What is an autosomal DNA test?
Genetic Predisposition testing
Another method of exploring your DNA heritage by taking a genetic predisposition test – these allow you to assess your genetic risk of developing medical conditions, from cancers and chronic diseases, to allergies, intolerances, and ailments like back pain. There are a number of private companies that offer genetic predisposition testing in our health section, so you can see what the likes of Veritas Genetics offer.
One well publicized example of a condition that you can be genetically predisposed to is breast cancer. Although anyone can suffer with breast cancer at some point in their lives (even men), the level of risk varies from person to person. If you were to inherit certain genetic variants in the ‘BRCA’ genes from your parents, your risk could be significantly higher than average.
Fortunately, a genetic predisposition test can reveal the presence of these ‘problem variants’, and help you prepare for the future. In 2013, actress Angelina Jolie revealed that she had undergone a mastectomy in response to the results of such a test. Since then, the number of people using genetic predisposition tests to screen for problem variants in the ‘BRCA1’ and ‘BRCA2’ genes has increased by nearly 40%.
Something worth pointing out is that testing for problem variants in the BRCA genes is a rare example of a genetic test that you can potentially get for free. If one of your close relatives has already tested positive for these variants, or you have a history of breast cancer in the family, you may be eligible for a genetic predisposition test on the NHS. If this is something you’re keen to explore, we recommend that you discuss your options with your doctor.
Something worth pointing out is that several health insurance companies now cover part of the cost of testing for genetic variants in the BRCA genes, providing you have a strong familial link to the disease. If you’re interested in a genetic predisposition test and you think you might be eligible for this type of coverage, it’s worth getting in touch with your health insurance provider before purchasing. If your insurance doesn’t cover the cost, or you don’t have health insurance, there are other ways of reducing the price of the test, and you should discuss your options with your physician.
What does the term ‘genetic predisposition’ actually mean?
There are a few things that you should be aware of if you’re considering a genetic predisposition test. Firstly, it’s important to understand that in most cases, carrying a genetic variant that’s associated to a medical condition doesn’t necessarily mean that you will go on to develop it. The results you receive will show how much more or less likely than average you are to suffer with the condition, according to the current published research.
If you’re facing an increased risk, the company conducting the test will normally tell you what you can do to reduce these risks. On the other hand, if your test reveals that you’re facing a decreased risk, it’s worth bearing in mind that this doesn’t mean you’re immune to the condition.
Once you’ve identified your ‘genetic risk’ of suffering with a medical condition, you should bear in mind that this is not the whole story. For the vast majority of conditions, many non-genetic factors can affect your risk e.g. your diet, your weight, whether you’re a smoker.
If you’re considering a genetic predisposition test for an incurable condition such as Alzheimer’s disease or Parkinson’s disease, it’s important to think carefully about the repercussions of discovering you have an increased risk. Many people who’ve seen elderly relatives suffer with such conditions have wanted to know if an increased risk is part of their DNA heritage, whilst many others would prefer not know. There are many benefits to identifying a heightened risk to an incurable condition – you may wish to try new treatments to mitigate its onset, plan your retirement differently, or sign up for trials in order to help seek a cure. On the other hand, if you discover you have a heightened risk, it’s not possible to ‘unknow’ this information, and you may be better off not knowing than learning about something that’ll cause you stress and anxiety.
If you purchase a genetic predisposition test through your medical professional, you’ll normally receive genetic counseling both before and after you take the test. This will allow you to learn about the potential outcomes of the test and ask any questions beforehand. Once the results are in, you’ll have the support you need to explore your options moving forward.
If you purchase a genetic predisposition test through a private company, make sure you check their website to see if genetic counseling is part of the service. Though many company websites will explain the test, its limitations and the potential outcomes, for serious medical conditions, we’d strongly recommend you buy from a company that offers ‘face to face’ or phone support, once you receive your results.
As well as testing for your own predisposition to medical conditions, you may wish to undertake ‘carrier screening’ to assess the risk of your passing on conditions to your children. One of the most common types of carrier screening is for cystic fibrosis, a condition which is caused by a genetic variant in the ‘CFTR’ gene. You may discover that although your partner and yourself do not suffer with a medical condition, you may both carry a problem genetic variant that means there’s a chance that your children will develop one. If this turns out to be the case, there are measures you can take, such as IVF with preimplantation genetic diagnosis, to reduce the chances of your child inheriting the condition.
It’s worth noting that many genetic ancestry companies will let you download your digitized genetic data after you take their test: 23andMe, Family Tree DNA and Ancestry.com are three such companies. By downloading your ‘raw data’ (a zipped file that’s normally under 20 MB) you’ll be able to upload it to a number of third parties that can re-analyse it for free or for a small fee. This will often reveal additional information about your ancestral heritage, or potentially identify new genetic variants that are associated to an increased risk of suffering with a medical condition.
Tests for your genetic heritage aren’t limited to those that uncover your ancestry or establish your risk of suffering with (or carrying) a medical condition, they can also be used to reveal the physical and psychological traits that you’ve inherited.
The most popular trait tests are those that can provide training or nutritional plans that are tailored to your DNA, to help you achieve your fitness goals. This type of testing is possible because a number of the genetic variants that you’ve inherited are linked to how effectively you respond to certain types of exercise, your predisposition to injury, and your metabolism. If these types of test are of interest, then check out the companies selling fitness and diet DNA tests such as Fitness Genes and DNAFit.
Other tests for inherited traits will report on your caffeine metabolism, earwax type, hair curl, and all sorts of other physical characteristics that make up your genetic heritage. Many of the traits you can test for may be interesting but won’t impact your life whatsoever. On the other hand, if you’re concerned about male pattern baldness and you wish to test for this trait, taking a test may allay your fears or encourage you to seek treatment options while you still can!
There are also genetic tests for your personality traits which can reveal the characteristics that are part of your genetic heritage (nature) vs. those arising from your upbringing (nurture). Genetic personality tests are relatively new, but the studies supporting the associations between genetic variants and aspects of your character are growing in number. You can test for traits such as confidence, spontaneity, optimism, sex drive, aggression, and many many more! Some of these tests will also include a personality quiz to take non-genetic factors into account, to give you a more accurate picture of the psychological forces at work.