DNA Testing – Step 5
If you are looking for your birth family, doing DNA testing is an absolute must. DNA tests will give you DNA matches in the form of “possible 3rd cousin” type results but won’t tell you who the common ancestor is or when they lived. You will need family tree’s and help from you matches for that. What it will do is confirm that are related to the list of matches it gives you. It can save time and money narrowing down who you are looking for. Watch the video at http://findmyfamilymagazine.com/get-started-genetic-genealogy-video/ for a good idea of what information DNA will give you. You should buy an atDNA test from at least Ancestry.com. At Ancestry you will be able to get DNA matches, see other matches you have in common, view family trees, and use mirroring – http://findmyfamilymagazine.com/mirroring-to-find-birth-family/ to attach your DNA to the family tree of your matches to see if you can get more information. You can read reviews of the 3 main DNA testing sites we suggest.
You send in your DNA in the form of saliva or cheek scrapings to one of the big three companies to identify which DNA traits you carry. They only analyze a small but key part of your DNA for identifying markers. What do you do with this information after the results are in? How do we take the reports and the list of matches we are given and use it to find our family members? To understand what we need to do with the DNA results, we need at least a little understanding of DNA and what it is comprises.
In humans, a cell nucleus contains 46 individual chromosomes or 23 pairs of chromosomes. Half of these chromosomes come from one parent and half come from the other parent. The first twenty-two of the pairs of these are called autosomes (Autosomal DNA); the final pair of chromosomes are the sex chromosomes, X and Y. The sex chromosomes determine whether you’re a boy or a girl, females have two X chromosomes while males have one X and one Y.
Like chromosomes, genes also come in pairs. Each of your parents has two copies of each of their genes, one from each of their parents. Each parent passes along just one copy to make up the genes you have. Genes that are passed on to you determine many of your traits, such as your hair color and skin color. These are passed down to offspring in different combinations so that you and a sibling may have very different traits. Just think about the traits your grandparents have like hair color, freckles, big hands, green eyes, and which traits you probably got from which grandparent.
The amount of DNA that is passed down from each parent cannot be predicted exactly. In general, each of your parents contributed half of your DNA, so a sibling would have 50% of the same DNA, but it doesn’t work that way. DNA research shows a range of DNA that should match siblings with an average of 50%. Research has also identified the averages of each relationship like sibling, 1st cousin, aunt or uncle, that can be used to predict the relationship of matches. Here is a good article that explains why you share 46-54% of your DNA with your sibling, but you may have different DNA matches http://genetics.thetech.org/ask-a-geneticist/siblings-are-around-fifty-percent-related.
Different pieces of DNA comes from different ancestors. This is why you might have your maternal great-grandfather’s mouth and your paternal grandmother’s nose.
Your DNA contains a pieces of your ancestors DNA, but you aren’t an exact copy of any one of them. The mix of DNA you inherit is unique to you, no two people can have the same DNA unless they are identical twins. If you go back far enough, there is a chance that you inherited no DNA from a particular ancestor.
You want to take advantage of this fact that you are passed down pieces of DNA from your ancestors and match up your pieces of DNA to your matches pieces of DNA and see where you overlap. If you had your test done at Ancestry.com, you will need to download your raw DNA to a website or software program that has a chromosome browser. Regardless of where you tested, we suggest you upload your raw DNA to http://GEDMatch.com GEDMatch.com and http://dnaged.com/ DNAGED.com. If you tested with AncestryDNA, we suggest you also upload your raw DNA to Family Tree DNA.com. If you tested at multiple sites, upload the raw DNA files from all testing sites to GEDMatch. The three major testing sites test a different amount of segments and some use different testing tools, so go ahead and load all the results. I tested at the three major sites and loaded all of them to GEDMatch and there are slight differences showing in the results. The most obvious difference is that a match will sometimes show as a different distance of relationship. For example, they will show as a 3.6 cousin from 23andMe and a 3.8 cousin from Ancestry.
Sometimes FTDNA will offer to let you transfer your DNA file for free and use their tools, but usually they charge $39. This is well worth the money to use their Chromosome browser tools and to be able to have other potential matches from their million users. If you are looking for family, it is important to fish in as many ponds as you can afford. Each company has different algorithms and criteria on what they consider a match or not. Some of them, like 23andMe, do a better job of looking at overlapping segments instead of just number of matching segments.
When you see your results in a chromosome browser lie FTDNA, you see a simplified, flattened depiction of DNA segments. Thus a chromosome browser view of a chromosome shows the two sides of the chromosome laid on top of each other to depict the segment locations.
Sex Chromosomes X and Y and Testing
Unlike the other 22 chromosomes, the 23rd pair of chromosomes, the sex chromosomes, follow exact patterns of how they are passed down. If you are female, you got an X from your mother and one from your father, making you XX. If you are male, you got an X from your mother and a Y from your father XY. The X-chromosome is passed down from a mother to sons and daughters. A male cannot pass an X-chromosome to a son, he can only pass a Y chromosome which is never passed to or from a female. Autosomal DNA potentially shows DNA cousin matches to ALL ancestors for 6-8 generations, and sometimes further back. Both male and female. If you decide to get mtDNA testing that will ONLY show your maternal line – your mother, her mother, her mother and so forth. The same goes for YDNA testing if you are male. If you are adopted and looking for your birth relatives, I don’t suggest you get the mtDNA or YDNA tests unless you want to know more about ancestors way back several generations. They won’t help you find your immediate family. For example, I had hundreds of matches on all three testing sites on my atDNA, but only 2 matches on my mtDNA and both of those were women from European countries and we have no idea how we are related, it must be back 10 or more generations.
For a great primer in DNA visit http://sites.google.com/site/wheatonsurname/beginners-guide-to-genetic-genealogy
Before you get too far in to information gathering, take time to watch the webinar by Diahan Southard about Organizing Your Genetic Genealogy. This will save you time in the long run by being better organized from the beginning. Http://familytreewebinars.com/download.php?webinar_id=272