DNA Basics. OLLI: Genealogy 101 October 1, ~ Monique E. Rivera ~

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1 DNA Basics OLLI: Genealogy 101 October 1, 2018 ~ Monique E. Rivera ~

2 WHAT IS DNA? DNA (deoxyribonucleic acid) is found in every living cell everywhere. It is a long chemical chain that tells our cells how to grow and act. DNA is divided up into chromosomes (major blocks) which are then divided into genes. Humans have 23 pairs of chromosomes (46 in all) arranged in a double helix. We each get 23 chromosomes from our mother and 23 from our father. In humans, the 23rd chromosome is either an X-chromosome or a Y-chromosome, and determines if we are male or female. Women have two X-chromosomes, while men have one X-chromosome and one Y-chromosome.

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4 When it comes to DNA, there are three types of tests...

5 TYPES OF DNA TESTS Autosomal DNA: DNA that does not contribute to gender; it is the first 22 pairs of chromosomes. Because it does not rely on the 23 rd chromosome, autosomal DNA tests can be done in both men and women with the same results. Main Uses: to determine how closely related you are to someone else and to provide an estimate of your ethnicity, or the regions of the world where your ancestors lived (e.g., over the past few hundred years, or even a thousand years, since people used to move a lot less often).

6 mtdna: Mitochondrial DNA (mtdna) is passed down from your mother; it ignores the main DNA in a cell and looks at the DNA of the mitochondria instead. It tells you about your mother s mother s mother s mother, and so on, back through time. An mtdna test will identify how closely related you are to a haplogroup. A haplogroup is a group of people with a single common ancestor. Historically, everyone living in the same region might belong to the same haplogroup, or very closely related ones. This means that your haplogroup can identify where your maternal line originated.

7 Y-DNA: The 23 rd human chromosome has two versions, the X and the Y. Women have two X-chromosomes, while men have one X and one Y. Y-DNA tests examine only the Y-chromosome. Because you can only get a Y-chromosome from your father, and he from his father, that means it tends to change very little over time. Because the Y-chromosome is only passed down through males, the test can only tell you about your direct paternal line. Y-DNA testing is especially useful for adoptees as well as Jewish ancestry.

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9 WHICH TEST IS BEST FOR YOU? It all depends on what you want to know.

10 Autosomal DNA For most genealogists, the autosomal DNA test is the winner; it is the one test that every testing company offers. Because your autosomal DNA comes from all of your ancestors, this test is good for finding a range of ancestors and living relatives. It can also provide you with reasonable estimates of the ethnicity of your ancestors, or the regions of the world where they lived. Most of the time, an autosomal DNA test is only useful for about five generations that is, to your great-great-great-grandparents. In terms of living relatives, that means it extends to your third cousins or maybe fourth cousins. Combined with websites that let you connect with close matches, autosomal DNA can provide some great leads on finding others who are researching the same family tree as you. mtdna Because mtdna comes to you only from your mother, and from her mother, it only helps you trace one line. You can use it to prove a common ancestor with someone else, but only in a direct maternal line. It can, however, trace that line back a very long way sometimes 10,000 years or more. That can provide evidence that your mother s maternal line came from a very specific region or ethnicity. But it is less useful when finding living relatives. The mtdna test also tends to be more expensive. Y-DNA The Y-DNA test follows a direct paternal line. A Y-DNA test can tell you about your father s father s father s father, and many generations before that, but not about any of your other ancestors. Y-DNA is most useful if you want to prove a connection to a certain ancestor. Like the mtdna test, Y-DNA may let you trace a line back for dozens of generations. It can also tell you the ethnicity or region of origin of your paternal line. Only males have Y-DNA, so only males can take the test. A woman can still find Y-DNA results by having a close male relative take it for her, such as her brother, father, paternal uncle, or cousin by a paternal uncle (but not her son, since he got his Y-chromosome from his paternal line, not hers). You can also trace other paternal lines by asking an appropriate family member to take the test and share the results with you.

11 Best DNA Tests Updated: September 2018 AncestryDNA: Best for cousin matching, most geographic regions for ethnicity FamilyTree DNA: Best for serious genealogy, YDNA and mtdna tests MyHeritage: Best autosomal test on a budget 23andMe: Best for genetic health screening, not genealogy Living DNA: Best for roots in British Isles

12 How is DNA collected? AncestryDNA: Saliva sample FamilyTree DNA: Cheek swab MyHeritage: Cheek swab 23andMe: Saliva sample Living DNA: Cheek swab

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14 September 12, 2018 AncestryDNA released updated ethnicity estimates for all customers. The size and makeup of the reference populations grew: ~3,000 reference samples > ~16,000 reference samples The update added 17 new regions to the ethnicity analysis 363 > 380 regions Many regions were redefined or their names were changed to more accurately reflect the region. The method by which AncestryDNA calculates ethnicity changed -- the algorithm now uses stretches of DNA to perform the calculation instead of individual SNPs (small chunks of DNA).

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16 In this example, several regions were lost, several regions were gained, and several regions were combined together and/or their names were changed.

17 Regions versus Countries DNA tests will often give you a region of origin and not a country WHY? Countries have changed many times throughout human history, in addition to migration and intermarrying across borders. For example, a DNA testing company may not state Germany or France, yet they will state continental Western Europe.

18 Please remember: The accuracy of estimates is constantly improving as more data are collected; there s no clear indication that one company is more accurate than the others. When a company does improve its ethnicity estimates, your profile will automatically be updated, too. You won t have to retake the test to get the new results, but you will have to visit their site. As more and more data get collected, companies update their regions, too. The companies that provide DNA testing divide the world up into regions in different ways. Most companies currently use regions, but the number, location, and names of regions vary from company to company. That means that two different testing companies may give you different ethnicity estimates for the exact same DNA.

19 Let s review an AncestryDNA Summary as an example...

20 GEDMATCH: