Health and disease info: DNA testing can also indicate which conditions for which you may have a preponderance. It's a controversial feature, to be sure. Knowing that you have a genetic predisposition to a certain form of cancer may make you more vigilant for testing, but it may also lead to increased stress -- worrying about a potential condition that may never develop, even if you're "genetically susceptible" to it. The possibility of false positives and false negatives abound -- any such information should be discussed with your doctor before you act upon it.
These tests can reveal the migratory paths of your paternal and maternal ancestors after they left Africa 200,000 years ago. By studying the migratory route they took, this can help you identify the ethnic groups they may have been part of. That said, as your paternal line is your father’s father’s father etc., and as your maternal line is your mother’s mother’s mother etc.; your paternal and maternal ancestors represent a smaller and smaller proportion of your ancestry the further back you go (just one sixteenth of your total ancestry five generations ago). Therefore, tracing your migratory paths back thousands of years may provide insights, but they’re a poor means of exploring your ethnic mix.
Similarly, mitochondrial DNA, or mtDNA, is used by direct-to-consumer DNA tests to trace your direct maternal lineage and determine maternal haplogroups. While most DNA lives in your cells' nuclei, mtDNA lives in the mitochondria. Mitochondria are the cells' powerhouses – their 37 genes are necessary for cellular energy production and respiration. Previous research suggested that mtDNA is inherited directly from your mother, but a recent study found that biparental mtDNA may be more common. This discovery may affect maternal haplogroup testing in DNA tests in the future, but for now, it’s safe to assume your results are correct.
Of the 23 pairs of chromosomes in the human genome, 22 are autosomes. Most direct-to-consumer DNA tests look primarily at your autosomal DNA to determine your geographic ancestry percentages. This DNA is a mix of inherited DNA segments – half from each parent. Because everyone inherits at least one X chromosome from their mother, DNA tests often include the X chromosome in autosomal testing, though the X chromosome is not an autosome.
Consult a doctor on any health data: Cancer. Leukemia. Heart disease. Alzheimer's. There are a lot of scary afflictions out there, and your DNA testing may well indicate which ones to which you are genetically predispositioned. But the data from DNA testing exists in isolation. You should consult your doctor to explore the data from any of these tests. They'll help you determine how to implement any lifestyle changes or followup testing as a result, if it's worth doing so.
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— Once you have chosen a test and received your autosomal results there is still a great deal more fun to be had. Independent tools and websites created by scientists and enthusiasts allow you to take the raw data provided from FTDNA, 23andMe and Ancestry DNA and explore them in astounding detail–giving you a wide variety of new admixtures, phasing options, chromosome browsers, SNP tools and connections with family across the world. Gedmatch is our favorite because they have so many wonderful and meticulously updated tools from a variety of sources. Easily upload your raw data and run your results for free (if you love the tools, don’t forget to donate and uncover even more options.)