yDNA - This is male Y-chromosome DNA which is passed with few changes from father to sons forever. Because, in almost all cultures and societies, the father's surname is also passed on to the son, yDNA is the basis for almost all surname DNA projects. Since there are many existing yDNA Surname Projects, your results will most likely match one of the one or more of the project participants with your surname. In general, if two or more participants have matching yDNA, these participants are termed a "group" in the project. However, there are several reasons that you might not match an existing project participant or group. These reasons and other yDNA particulars are discussed on this page. In our experience, these anomalies occur for about 10 to 15 percent of the participants. From a genealogical perspective, the good news is that even if your yDNA does not match anyone with your surname, it most likely will be an obvious match with participants in a different surname project. In any case, valuable genealogical information is nearly always obtained from the results of yDNA testing. Most of the yDNA testing companies offer tools to compare your yDNA results to the results of the other participants in their database.
            When considering ordering a yDNA test, it is very important to know that yDNA "marker" suites/groupings have not been standardized or agreed on by the various DNA testing companies. That is, different companies test for different markers. In yDNA analysis, the more comparable markers, the better; however, incomparable markers are completely useless, no matter how many of them are tested. Our project accepts yDNA results from any testing company, but before you order testing, check the number of comparable markers that you are paying for.

            mtDNA - This is Mitochondrial DNA which is passed virtually unchanged from mother to daughter forever; however, because the female surname changes almost every generation, the female lineages are very difficult to trace and the few mtDNA projects that exist are mainly based on geography. However, mtDNA is extremely stable with almost no mutations and, for this reason, it is considered the most reliable anthropological DNA test. mtDNA is also passed from mother to son, but the son does not pass this mtDNA to his son or daughter. That is, a son has his mother's mtDNA. Do not confuse the mtDNA with X-chromosome DNA (xDNA).

            xDNA - This is X-chromosome DNA that is passed from mother to daughter and son and also from father to daughter, thus a female receives one recombined X-chromosome from her mother and one X-chromosome from her paternal grandmother, via her father. This transference pattern produces a rather unusual XDNA inheritance trail. In any generation, the male's paternal ancestors are eliminated as xDNA contributors since the male can only receive his xDNA from his mother. Some of the companies that test and report atDNA raw data also test and report xDNA raw data. GEDmatch can use uploaded xDNA raw data to search for matches. Because of the unusual xDNA transmission characteristics, these matches can be used effectively as an eliminator of possible ancestor DNA trails. Do not confuse X-chromosome DNA (xDNA) with mtDNA.


            atDNA -  To begin with, we are only slightly interested in the medical, anthropological, admixture, etc. prediction aspects of atDNA testing, so these characteristics do not weigh heavily in our following discussions. Secondly, we cannot over emphasize the difficulty usually involved in determining any meaningful family history information from the analysis of atDNA results. By meaningful, we mean the discovery and/or confirmation of new or suspected/unproven ancestors. Obviously, the laws of probability dictate that a very few people will find meaningful information with ease, but this will not be the case for the vast majority of atDNA participants. If you find the following discussion tedious, tiresome and boring, you will most likely feel the same about the atDNA results analysis process itself. This should be a wake-up call for you.
            atDNA tests are suitable for males and females because humans have 22 pairs of atDNA chromosomes and we inherit atDNA chromosomes from both of our parents. One chromosome from each pair comes from our mother and the other is from our father. So each of our parents carry 22 pairs of autosomal chromosomes (atDNA): On average, one half of each pair came from their father, the other half from their mother. That is, our mother carries one copy from her own mother and one copy from her own father. Likewise, our father carries one copy from his own mother and one copy from his own father so, on average, every person gets about half of their atDNA from each of his or her parents. Since our parents each carry 22 pairs of chromosomes, 44 chromosomes are involved in a transfer in which we end up with 22 pairs. So, on average, 50% of each parents atDNA is lost in the transfer through the processes of random combination and recombination of the chromosomes. This is why siblings will probably have the same atDNA, but in different amounts. The most significant point is that atDNA dilution occurs rapidly from one generation to the next and the detection of matches get more difficult as relational connections grow more distant. atDNA does not include mtDNA, xDNA or yDNA chromosomes; however, some testing companies are rumored to include the results of X-chromosome (xDNA) tests in their relationship matching predictions. As discussed, on average, every child receives about 50% their atDNA from each parent; however, this figure can be very deceiving since the transfer of individual atDNA segments can vary from 0% to 100% and this transfer characteristic is completely random. Even rather large segments can be completely lost from one generation to the next. Matching individuals segments is what atDNA analysis is all about, so this unpredictable atDNA transference characteristic creates rather odd situations. If any generation suffers a 0% segment transference event, this atDNA information is lost forever. On the other hand, when one or more generations have very high segment transference rates, these segments are extremely useful in atDNA results analysis. So the cousin detection rate/capability of any atDNA result is heavily based on the random probability of atDNA segment transfer. Most testing companies estimate that, on average, atDNA testing has a 90% chance of detecting a match with a third cousin and about a 50% chance of detecting a match with a fourth cousin. Again, these are average percentages and, as discussed, they can and do vary quite dramatically in either direction.
            On the surface, this detection capability seems like a great tool; however, most people, if they think about it at all, vastly overestimate the chance of identifying their matching relative connection and/or deriving any useful family history information at all from atDNA results. This is because they are accustomed to researching their paternal direct line and to the utter simplicity of yDNA test results analysis. Most family historians research their direct male line from themselves back to the oldest ancestor (progenitor) that they can discover. After this discovery, some research the other male descendants of the progenitor. Most virtually ignore the female descendants of the progenitor because many researchers consider this research to be the job of the researcher of the husband of the female. Most virtually ignore the ancestors of the spouses of the progenitor's descendants. Most do not completely research their maternal line because of the difficulty associated with the generational name changes of the females. However, we carry the detectable atDNA of many of our ascestors, as do the thousands of their other descendants (our cousins). The excellent diagram on the right was created by Angela J. Cone to illustrate the dilution characteristic of atDNA; however, it is also useful in illustrating the the array of ancestors that contribute atDNA to you and your matches. Your direct surname line might be the mostly blue trail at the far left; however, it is apparent that the direct branch contains only a small percentage of the entire array of your potential atDNA matches. Also note that the array contains all of your female ancestors, paternal and maternal, so many of your atDNA matches will led to connections with common female ancestors. One regrettable aspect of many otherwise well researched lineages is that females ancestors and their descendants are virtually ignored. If you or your match/relative have not researched your female ancestors, the match will be virtually useless unless significant additional traditional research is done. Next, remember that each generation of the array is apt to have multiple children and, in general, this leads to thousands of descendants of the progenitor and thousands of similar diagrams, each depicting a slightly different lineage. So, when the testing company reports that you have an atDNA match, you know you have a common ancestor; however, the question is this: Where in the multiple arrays does this common ancestor reside? Because your atDNA match could be with any of these thousands of descendants, you really need more than an ancestral GEDCOM and/or a list of surnames. What you really need is a descendant chart that includes all of your thirty-two 3rd great grandparents and their descendants or, better yet, one for all of your sixty-four 4th great grandparents and their descendants but, if you had such a chart, you probably would not need to do atDNA analysis. Most family lineages do not contain the names of even a tenth of the total atDNA carrying descendants. So, even if you and your match each have recorded a tenth (probably wildly optimistic) of your ancestors, that leaves ninety percent unknown. Therefore, even if the lineages of two matching atDNA participants are compared, you and your match will need considerable luck to identify your relationship and your common ancestor. It is much more than likely that you both will be unlucky and it may extremely difficult or impossible to ascertain how you are connected. To aid in the atDNA results analysis process, it is very useful to have parents or grandparents tested; however, since this is impossible for many people, it is also helpful to have children and close cousins tested. Obviously, this added analysis testing is beyond the financial capability of many people.
            So, the statistics of the situation make the odds of exactly identifying your atDNA match connection quite unlikely, but there is much more to this story. To have any chance at all of success, you will almost always need to understand the three step atDNA results analysis process.
            First - the testing company compares your atDNA results with the companies entire database of atDNA participants to find matches. The testing company then evaluates the matches and makes suggested relationship predictions (e.g. uncle, 2nd cousin, 4th cousin, distant cousin) for you and all the matches. These matches and relationship predictions are then made available to you. This step works very well; however, you should be aware that most of your matches will be with 4th and more distant cousins. It is not unusual that some suggested matches will be coincidental instead of relational. The more distant the suggested relationship, the more likely the match will be coincidental. 
            Second - YOU compare your lineage, ancestral surname list or GEDCOM of your DNA providers to a similar resource that your match/relative has hopefully provided. These ancestral lineages, surnames and GEDCOMs come from the quality research that you and your match/relative have supposedly done. Hopefully, you will have a complete name or surname in common which may be the link to your relationship connection and your common ancestor. YOU must decide which matches might prove fruitful and thus be follow-up candidates. To make these decisions, YOU will probably need to understand and utilize a chromosome browser, a triangulation tool and other analysis tools to compare atDNA test results.
            Third - YOU attempt to discover the connection with your match. If you cannot identify the connection from the lineage, GEDCOM and surnames provided by your match, you may attempt to contact your identified match and work with that person to try and identify your common ancestor. Hopefully, this person will also be interested in the match and will have the skill, time and patience necessary to discover the connection with you. Unfortunately, for many/most matches and for a variety of reasons, this will not be the case, but if you and your cooperating match are diligent, you may discover a potential connection. Even though many people assume that the matching atDNA and an apparent common ancestor in a lineage, surname list or GEDCOM are proof of a particular relationship, this is not the case at all. In reality, it is entirely possible, or even likely, that you and your match have several common ancestors and the atDNA match could be with any one of them. This possibility grows significantly more likely with more distant relatives/connections. So, if one or both of the lineages, GEDCOMs or surname lists that are being compared have not been well researched or is incomplete, the matching atDNA may be from an common ancestor that is unknown to one or both of the participants. Unfortunately, at least one testing company reinforces this misconception by "hinting" at a common ancestor without openly explaining the possibility of other common ancestors. This situation can and does lead to incorrect lineages that have been mistakenly "proven" by atDNA. To prove a connection, more conventional research and/or atDNA analysis will likely be necessary. Skill and patience with a chromosome browser and other analysis tools are essential. Also, since multiple ancestral connections are likely, well researched and complete lineages for all progenitor branches are essential to help prove a match.
           
            Under optimal conditions, this rather involved process can work well and a few success stories are alleged, especially when the joint research is not necessary or is relatively easy and quick. Almost all of the success stories that we have seen come from avid serious genealogists and DNA gurus with well researched family trees and with several/many close relatives who have also taken atDNA, yDNA and mtDNA tests. The DNA results from these relatives are used to attempt correlation of atDNA segments with particular ancestors. In general, this is an expensive and time consuming process. These guru "case studies" are extremely far from typical and represent only a very tiny fraction of the atDNA test participants. Moreover, most participants do not have the resources to pay for multiple DNA tests. At the other end of the testing participant universe are those with little or no near-term family history (i.e. orphans, etc.). For this small fraction of participants, atDNA test results and analysis will most likely provide a number of matches/close relatives that may be very significant. However, for the vast majority of participants, Steps Two and Three described above have several significant failure mechanisms that hinder success. As mention above, considerable luck is initially involved because the process depends on matching your atDNA with the atDNA of another participant that can help you in one way or another. If the matching relative that you have identified as a fruitful possibility is not interested in shared research or does not have the required resources (i.e. skill, time, focus, patience, quality lineage research), your only recourse is to move on. If you are lucky and a high potential match is identified and recruited, the research that follows will frequently require significant skill, time and patience on your part and that of your newly identified match/relative. In most cases, your success will depend on your expertise with atDNA analysis tools. Some of the testing companies provide analysis tools to assist your research. These tools seem to be effective, but also take time and patience to understand and use. Many people find these tools difficult and impossible to understand and use. In our experience, many people find the entire process to be very tedious, time consuming and beyond their level of skill. They become overwhelmed and their patience is soon exhausted. Because of their complete lack of knowledge concerning atDNA result analysis, many people quickly give up in frustration, even though they may have significant discoverable connections that might advance their family history. The opposite situation also occurs frequently. Some participants are unable to discover any meaningful matches at all. This usually means that few or none of their relatives have taken an atDNA test or have included a lineage, GEDCOM or surname list. This is also a frustrating experience and the tests are soon forgotten even though there is a very good chance of a future match. Unfortunately, this lack of success with atDNA testing and analysis usually produces a lasting distrust of all DNA testing products.            
          
            The International Society of Genetic Genealogy (ISOGG) has published an online chart that compares many of the  product characteristics of the major DNA testing companies. This informative chart is here; however, our experience has led us to believe that the selection of a testing company is the least important aspect of the total atDNA testing/analysis process. This does not imply that you should ignore the negative implications associated with a company that does not publish an easily discoverable Customer Support telephone number or email address. All of the testing companies seem capable of determining your atDNA and presenting you with this information (Step 1, above). Next, you must implement Steps 2 and 3 described above. This is where the rubber meets the road. The rather recent availability of an independent source of atDNA analysis tools has somewhat leveled the playing field with respect to the technical aspects of DNA analysis. GEDmatch has developed several free (donations accepted) tools for analyzing atDNA results. GEDmatch accepts uploaded raw atDNA and xDNA test data generated by 23andMe, FTDNA and Ancestry.com. Among the tools are an atDNA chromosome browser, a chromosome segment comparer, a phased data generator, a triangulation comparer and a GEDCOM comparer. Other tools may be developed. These tools can be very effective when utilized by people who have the skill and time to use them. To use any of these tools, YOU must download your raw data from your DNA testing company, then YOU must upload this raw data to the GEDmatch site and wait for the data to be processed. Next, YOU must analyze the data and YOU must then follow the identification and discovery procedures described above in Steps 2 and 3 above. Although the testing companies provide instructions for downloading raw data, some people are challenged by this requirement. The same comment applies for the uploading procedure. Currently, the GEDmatch atDNA database is is being populated by the customers of the major DNA testing companies at a seemingly incredible rate; however, we think that many of the GEDmatch users are looking for the magic that they did not find at their testing company site. Although GEDmatch provides more analysis tools than the DNA testing companies, none of these tools are magical. In addition to understanding these tools, analysis steps 2 and 3 (described above) are still required, along with a large dose of luck, skill, focus, persistence and  patience. Since individual atDNA results files are enormous, GEDmatch requires significant computation resources (computers & memory & programmers). Presently, it is obvious that these resources are being severely strained, if not overwhelmed at times. However, if the volunteer creators of GEDmatch can overcome their growth difficulties, the GEDmatch atDNA results database will hopefully provide a resource similar to the existing Ysearch database for yDNA results. Although the quality, availability and sustainability aspects of the GEDmatch site have yet to be proven over an extended period, this site could become a very important resource for the serious researcher possessing the abovementioned research traits; however, for the average or even the above average family historian, the magic will still elude them.