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Research and Verify Your Ancestors Using Genetic Genealogy (DNA)
HOW TO…
You’ve probably heard other genealogists talking about using DNA to assist with their research. One of the most recent additions to the genealogist’s toolkit is genetic testing. Like learning how to use the Internet and databases, you’ll want to learn about DNA and genetic testing in order to understand it and apply it in your own research. Because this chapter cannot possibly address everything about genetic genealogy, I’ll discuss some basic concepts and then refer you to other books at the chapter’s end that will provide you with an in-depth understanding.
We all have physical traits that distinguish us from one another. You’ve often heard the comment that someone has his mother’s eyes, his father’s hair coloring, or some other physical attribute. We know that genetics, the science of biology and heredity, plays a central role in how we are formed. Our genes provide the template for our physical development, from the single-cell fertilized egg to the human form that we become. The basis of this genetic template is DNA.
Learn About DNA and Its Place in Genealogical Research
DNA is an acronym for deoxyribonucleic acid, a chemical that is the blueprint for every cell in all living organisms and in some viruses. DNA molecules store the information and instructions for all the components of cells. DNA carries the genetic information, called genes, that is involved with how the entire organism is formed.
You may have heard the structure of DNA referred to as a “double helix.” DNA physically consists of two long strands of organic material called nucleotides. The nucleotides are formed from sugars and phosphate groups that are joined together. These long strands run in opposite directions and form the twisted double helix. One of four types of molecules is attached to each sugar in each strand, and these molecules are called bases. The sequence of the bases is the coding that determines the genetic coding for each cell. The coding is replicated into ribonucleic acid, known as RNA, a single strand of nucleotides.
DNA is organized into structures called chromosomes, and these building blocks are duplicated before cells divide and replicate themselves. All of this information is essential to the creation of life. Scientists have been working for decades to decode the genetic sequences and understand the function of each gene. The Human Genome Project began in 1990 with the goal of identifying all of the human genes and studying their physical structures and their functions.
Although this is a relatively simple description of DNA, it will suffice for the rest of the discussion in this chapter.
Both genetics and genealogy focus on heredity:
As you can see, the two research disciplines share a somewhat common goal. DNA has been used in medical and forensic applications for quite some time. Amniocentesis is a method in which a small amount of a pregnant woman’s amniotic fluid is removed and tested. It is an important procedure used to diagnose chromosomal irregularities and infections and employs genetic testing. Paternity tests use DNA to confirm or refute the relationship of a man to a child. We’ve also seen episodes of television dramas in which DNA evidence has been used to identify a body, to determine the relationship between individuals, or to link a suspect to a crime scene or a victim.
DNA in your genealogy can similarly be used to prove or disprove relationships between individuals and family groups. While not as precise as forensic DNA analysis, modern DNA testing for genealogical purposes has advanced to include more genetic marker tests. These provide a broader range for comparison with other people’s test results.
There are three timeframes with which DNA testing can help genealogists:
Each of the three time periods can provide insights into your genealogical research and your deep geographical and ethnic heritage. The modern era is the period in which you are most likely to be able to achieve the most value from DNA testing in your genealogical research. However, the testing also can identify your haplogroup. Haplogroups are the main branches of the human genealogical tree, and they consist of haplotypes. Haplotypes are closely linked genes and genetic markers that are shared by a closely related group of people. These people typically are from a specific geographical area and/or part of the same ethnic origin. Haplogroups correspond to early human migrations between distinct geographical regions. Your haplogroup is indicative of your deep ancestral origin. Figure 12-1 shows an example of a haplogroup report from Ancestry.com.
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FIGURE 12-1 Sample of haplogroup results
Discover the Difference Between Paternal and Maternal Testing and the Results
DNA testing, also referred to as genetic profiling or genetic “fingerprinting,” is used to identify individuals based on their DNA profile. You begin by deciding what test you want and investigating the companies that provide the test. One consideration will be the number of genetic markers you want tested and reported on. The price of the DNA test you want is based on the number of markers you want tested. Once you have made this decision, you can then order a test kit from a DNA testing company. It typically consists of two or more sterile cotton swabs, an envelope that you seal and label, and a return mailer. The physical test consists of rubbing the cotton swabs inside your mouth. Your oral epithelial cells and saliva contain DNA, and it is that which is captured on the swab. You return the swabs to the testing company and, after some weeks, you receive your test results.
The test determines the values of a set number of markers, and the resulting values can be compared against other people’s results. The test uses highly variable repeat sequences that can identify closely related individuals or differentiate between unrelated individuals. It also is used to study mutations in the marker values. It is both the similarities and the mutations that help determine the number of generations backward that there may be a “most recent common ancestor” (also referred to as the MRCA). The mutations occur at a comparatively regular rate, and these changes can be statistically used to project the number of generations between you and your MRCA.
It is important to know that humans, and most other mammals, have one pair of sex-determining chromosomes in each cell. Males have one Y chromosome and one X chromosome, while females have two X chromosomes. The Y chromosome is present only in males and can therefore reveal information only about the paternal line. The test for the Y chromosome is referred to as a Y-DNA or paternal DNA test. Figure 12-2 shows the results of my paternal DNA test.
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FIGURE 12-2 Sample of Y-DNA test results
Mitochondria are structures within cells that convert energy from food into a form that the cells can use. The mitochondria contain a small amount of their own DNA. This genetic material is known as mitochondrial DNA, or mtDNA. This mtDNA is passed only from mother to child, and there is usually no change from parent to child. It is therefore a powerful tool for tracing ancestry through the female line.
As a result, there are two primary types of DNA test available to assist in your genealogical research:
The Y chromosome can reveal that a man is related to other males—with the same surname or not. It indicates that there is a common male ancestor, but there may be no way to determine exactly how many generations back that the MRCA lived. The value, however, is in comparing your Y-DNA test results with other people’s results. We’ll discuss this later in the chapter when we cover DNA surname projects.
The mtDNA test allows you to undertake research into the records of your mother’s maternal ancestors. This can be a daunting task. However, the mtDNA test results can be used to definitively confirm your research and the relationships in your maternal lineage (see Figure 12-3).
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FIGURE 12-3 Sample of mtDNA test results
Another test is the autosomal DNA test. This test has only recently been introduced but it is important for genealogists. While the Y-DNA and mtDNA tests are dependent on the markers found on the Y-chromosome or in the mitochondrial DNA, the autosomal DNA test checks the additional 22 pairs beyond those that are sex linked. An autosomal DNA test is most effective when people share comparatively recent common ancestors.
It is important to know that we inherit, on average, 50 percent of the DNA from each of our parents. Since our parents also inherited, on average, 50 percent of each of their parents’ DNA, we can be certain that the DNA we inherited from our parents contains markers reflecting approximately 25 percent of our grandparents’ DNA. The autosomal DNA test is used to study the marker code values of those 22 additional pairs of chromosomes, and then it is possible to compare those values against other people’s test results to check for cousinship. First- and second-cousin relationships are almost certain to show up. The percentage of DNA from great-grandparents, great-great-grandparents, and more distant ancestors diminishes in each successive generation. Therefore, matches with third, fourth, and more distant cousins become less likely.
Genetic genealogy gives genealogists a means to check or supplement the historical record with information from genetic data. It can be used to solve gaps in your documentary research. However, there are other possibilities. A positive test match with another individual may:
As you can see, Y-DNA and mtDNA tests can trace ancestry on the paternal and maternal lines, respectively. The autosomal DNA test, however, can take your research into a more precise area. It also will provide you with matches from both sides of your family at once.
You should know that there is resistance to DNA testing by some individuals. The reasons may include:
You may want to seek the participation of other relatives to help expand your genetic genealogy research. Many genealogists encourage cousins, aunts, and uncles to submit DNA test kits, even offering to pay for the testing in order to gather more sample data. You may want to consider this incentive approach in order to extend the range of your genetic research.
Learn About Genetic Testing Services
There are many commercial DNA testing services available. You will want to conduct a little research about the types of tests and the number of markers tested, the price of the tests, and any affiliations they may have with other companies and/or with surname DNA projects on the Internet. You may, in fact, be able to obtain a lower price as part of a surname group, discussed in the next section. Prices differ between the different types of testing, and prices also vary between testing services, dependent on the number of markers tested and other factors. Some of the companies offer a combination of tests together in a bundle at a package deal price. You want to select a testing service whose results are specifically used for genealogical heritage purposes. A DNA paternity test kit and a forensic DNA testing service are not going to be of value to your genealogical research.
The following table lists some of the major DNA testing services for genealogists. Some of these are ethnicity-specific and provide specialized test results.
23andMe www.23andme.com
African Ancestry www.africanancestry.com
DNA Testing by Ancestry.com http://dna.ancestry.com
Family Tree DNA www.familytreedna.com
GeneTree www.genetree.com
Jewish DNA Central www.jewishgen.org/dna/
Oxford Ancestors www.oxfordancestors.com
Join a DNA Surname Project on the Internet
Genealogists who have had their DNA tested want to locate genetic matches to other researchers. This is particularly true of those who have had their Y-DNA tested and are seeking matches with others with the same surname and those who have had their autosomal DNA tested and wish to connect with cousins. A surname DNA project is the ideal place to make connections with other researchers.
A surname project is a genetic genealogical project in which the results from Y-DNA testing are used to trace male lineage. Surnames are passed down from father to son in many cultures, and Y chromosomes are passed from father to son with a predictable rate of mutation. People who share the same surname can use genealogical DNA testing to determine if they share a common ancestor within recent history. It is certainly possible for persons with a different surname to share the same Y-DNA test results. Don’t jump to any conclusions, however. Yes, there may have been an illegitimate child, but other factors may account for the discrepancy. There may have been a change of surname due to adoption; a man may have taken his wife’s name; frequent misspelling of an earlier surname may have resulted in a man taking another surname; a surname may have been changed by a male immigrant in order to “fit in”; or a nickname or alias may have been used and was then taken as the surname.
The results of a Y-DNA test checks the values of Y-chromosome markers. Depending on the number of markers tested, the results can be compared to someone else’s results and can reveal whether the two individuals share a common male ancestor. The number of markers tested and the number of matches at those markers can help determine the range of generations until their most recent common ancestor (MRCA) would be expected. Let’s say that two men are tested using 37 genetic markers. If the two tests match on 37 markers, there is a 50 percent probability that the MRCA was no more than 2 generations ago and a 90 percent probability that the MRCA was no more than 5 generations ago. A further comparison with other persons’ test results might indicate a familial relationship.
A DNA surname project takes the comparison another step. By joining such a project on the Internet, you not only share your test results, but also provide documentation of that surname in your ancestry back to the earliest known male ancestor in that surname line. The administrator of the project adds your test results into a grid that allows for easy comparison of each marker’s value with that of other people. The name of each participant’s earliest documented ancestor is included, as is the haplotype. (See the example in Figure 12-4.) The results are typically grouped together by haplotype and infer clustering. You can make contact with other researchers, usually with the project administrator acting as intermediary to help preserve each person’s identity and privacy until they both may indicate their desire to communicate directly. You can then share more detailed genealogical information and collaborate to further one another’s research.
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FIGURE 12-4 Portion of the Morgan Surname DNA Project page
Learn More About Genetic Genealogy
There is obviously much more that you can learn about genetic genealogy and using DNA test results in your research. There are several books available on the subject. I personally recommend the following titles:
The possibilities offered by DNA testing are increasing and improving each year. You will want to incorporate genetic genealogical research into your research toolkit, and gain another strong research facility for your family history.