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Genetics and Genealogy

Learn how genetics and DNA can help with your genealogical research.

Genetics and Genealogy

DNA testing for genealogical purposes is a fairly recent technological advancement, which can provide a means of breaking through “brick walls.” It also provides a level of scientific certainty of connections to family groups within a surname.

DNA has been used to identify people for many years in forensics, but tests for genealogical purposes were not publicly available until 2000. Advances have been made at a very rapid pace since then, though limitations still exist.

Genie Jargon

The Y-DNA Test is based on the Y chromosome, only present in males, passed from father to son. DNA is short for deoxyribonucleic acid—the genetic material of cells.

The Popular Y-DNA Testing

What is known as Y-DNA test is the major DNA application for genealogy at present.

Because this type of DNA is passed from father to son, it is ideally suited for single surname studies. Since late 2000, hundreds of such family projects have been established. For best results, it is best to go through one of these projects. They will have all the test results from studies conducted on the surname you are researching. And, their cost is less than doing it on an individual basis.

Genie Jargon

A haplotype, also called a DNA profile, is a set of certain values for genetic markers inherited as a unit. Haplogroups are similarly patterned and related descendant haplotypes that share a common ancestor and that suggest the geographic origins. Haplotypes and haplogroups can assist in defining the ethnic origins. Markers are specific positions on the DNA ladder that can be easily identified and measured.

You Gotta Be a Male

Y-DNA tests can only be done on males, as it is performed on DNA from the single Y chromosome, only present in males. This is the sex-determining chromosome. If you have it, you are a male. If you don't have it, you are a female. This DNA is passed on directly from father to son for many generations unchanged, as there is no input from any female parent along the line. This means that every male direct descendant of any man living many years ago will have an extremely similar Y-DNA pattern, called a haplotype. Aside from possibly connecting ancestry through haplotypes, test results will indicate a haplogroup. Tests consist of a certain number of markers; at least 25 are recommended—more of this later.

Are They Discriminating Against Females?

No, no discrimination. It's just a “fact of life” that females do not carry the Y chromosome. However, females (and males not descended from the surname in a continuous father-to-son descent) can still benefit by helping to sponsor tests for relatives that fit the requirement.

Lineage Lessons

Eligible males must be from an unbroken male direct line. That is, if the DNA project is for descendants of the Atkinson family, the only males eligible are those who had a father named Atkinson, a grandfather named Atkinson, a great-grandfather named Atkinson, and so forth. If the male had a great-grandfather named George Atkinson whose daughter Martha married George Mallory, and that couple had a son named Victor Mallory, Victor is not eligible to test for the Atkinson project. This is in spite of the fact that he is a male and a direct descendant of an Atkinson. It must be an unbroken male descent from the surname.

When you hear that the male being tested must “bear the surname,” keep in mind there could be unusual circumstances that create exceptions. In one early New York City Rose marriage, there was a divorce in the 1820s and the wife resumed her maiden name of Smith. The younger children took that name and remain Smith to this day. Some of these males who had a direct line from their Rose ancestor would in this case be eligible for the Rose testing project, in spite of their Smith surname. Another exception would occur in adoptions. In spite of the adoptee carrying the surname of his adoptive father, he would only be eligible for testing in the surname project of his biological father. There could be other reasons for a name change; the important factor is that the line be an unbroken direct male line through the surname.

Tree Tips

A minimum number of 25 markers should be tested for reliable results. This level is generally conclusive, providing a good degree of proof of relationship. Ten- or twelve-marker tests, available at lower cost, can often establish that people are not related, but cannot confirm that they are.

For example, Aldert Roosa was born in Holland, sailed to America in 1660, and settled in Ulster County, New York. He had several children, including four sons. All of his male descendants (those still carrying the surname, or those who changed the spelling to Rose or Rosa) will have an almost identical and distinct Y-DNA pattern. Additionally, all such descendants of Aldert's brothers and male cousins will also be very similar, even if their names are yet unknown. Thus, if two males named Roosa/Rose are tested, one with a proven line back to Aldert and the other whose line was unknown at the time of testing, and they turn out to have very similar markers, they can now be easily determined to be from this Roosa family. This has exciting implications. If Aldert Roosa, for instance, had a brother who remained in Holland, and a descendant of that brother tested and matched with a descendant of Aldert who came to the colonies, these branches could now reunite. The American branch would finally know of some of their relatives in Holland and could learn more about their heritage from those who stayed in that area. Those who had remained in Holland would have discovered through the test what may have been a “lost” branch of their family in the United States. Some believe that the origin of this particular Roosa family is in England or Scotland before going to Holland. Going a step further, the possibility exists that a male from England or Scotland may test and match the Holland male, or the American male, reuniting yet another branch and perhaps providing clues to the earlier origin. The possibilities are awesome, as the family Y-DNA projects expand and add tests from a variety of countries.

In confirming a line to a particular ancestor, it is necessary that at least one male line be well documented. Then, other tests that match the markers of that line are “proved” to be from the same ancestor.

Chipping in to Help

Females, and males who no longer carry the surname they are researching, can still participate in a DNA study by helping to finance a test for a male relative who is eligible. Results of a test from one known male relative of the surname effectively applies to all known relatives equally. It is in the best interests of all descendants to sponsor one or two tests from the family, preferably from different male sons of the progenitor.

To establish ties to an early family, it is only necessary to compare results of living individuals. Any two samples descended through different sons of any early progenitor can establish the DNA profile, or haplotype, of that ancestor. There is no need to obtain bones from the past!

What Started All This Fuss?

DNA was first identified in the 1950s. Over the following 20 years it became clear to scientists that this carried the blueprint for all life on Earth.

By the 1980s it had been established that DNA could be used very effectively for identification purposes, leading to widespread use in the fields of forensics and criminology. Only very small samples were needed, with sources varying from a body to traces left by a body, in what is referred to as “genetic fingerprints.” DNA paternal testing soon followed, effectively proving paternity far past the limits of earlier blood tests. A major achievement occurred in the early 1990s, with the exhumation and identification by DNA testing of the remains of members of the royal Romanoff family of Russia.

First public attention was brought to potential use of DNA as a genealogical tool in the late 1990s. Of special significance were efforts to determine if Thomas Jefferson was the father of some or all of slave Sally Hemmings' children.

A genetics study at the University of Arizona led to the formation of the firm Family Tree DNA in early 2000. A study by Dr. Brian Sykes of Oxford about the same time led to the formation of Oxford Ancestors. These companies were the first to offer commercial testing services to the public. Although a major turning point, these early tests were on a small number of markers, and thus somewhat limited in scope. However, this changed as tests were expanded to more markers. Testing of DNA from the Y chromosome (Y-DNA) became clearly the most advantageous for genealogical purposes, and surname projects became very common, providing the lion's share of testing. By 2002, Y-DNA testing quickly expanded to 21 and then 25 markers, creating a much higher degree of certainty than previously possible. Other firms also began testing; 37- and 42-marker tests became available in 2004.

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