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| No: 76 |
June 2012
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News June seminars 7: Genealogy on the Web, Mt Lofty Districts Historical Society, Stirling Library 10:00 to 11:00am 13: How to access English parish records from afar, Elizabeth Civic Centre Library 10:00 to noon 28: Heritage Walk—North Adelaide Cathedral precinct with refreshments @ the Queens Head Hotel (inc bus from Art Gallery to venue), Art Gallery of South Australia 10:00am to 1:00pm July seminars 5: Heritage Walk—Port Adelaide heritage precinct with refreshments @ the Port Dock Hotel (inc bus from Art Gallery to venue), Art Gallery of South Australia 10:00am to 1:00pm 28: Accessing the primary research stream — the family, Flinders University of SA 9:15am to 4:45pm See the seminar program for more details and bookings. here DNA Before you read this article, I need to declare that I am a sceptic about the usefulness of current genetic genealogy. I believe the process will improve with time, but at this point I suggest that the cost far outweighs the chances of a helpful result for the bulk of family historians. Many hope a DNA test will reveal their ancestry but they will end up with a document that tells them little or the bleeding obvious. The exception lies with those such as adopted people trying to determine their parentage or, to a lesser extent, people facing a barrier in their family tree because of two or more possible options and this is more in the field of forensic science rather than genealogy! In both these scenarios, supporting documentation is necessary as the DNA alone will rarely provide the whole answer. In writing this article I have, where possible, avoided any scientific terminology or explanations. |
In
this issue: |
Graham Jaunay Services
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| DNA tests have been around for many years, but it is only recently that the cost of genetic testing has finally become possible for the average individual interested in tracing their roots. Home DNA test kits can be ordered through the mail or over the Internet. They usually consist of a cheek swab or mouthwash to easily collect a sample of cells. The sample is returned through the mail and subsequently one receives the results which are a series of numbers that represent key chemical markers within your DNA. These numbers can then be compared to results from other individuals. All humans share about 99.9% of their DNA. It is in the remainder that you find the genetic variations that make you different. Sometimes, but rarely, a small change occurs in this portion of our DNA and this is then passed down the person's descendants. If a similar mutation isfound in two people's DNA it suggests that they share an ancestor somewhere in the past. Thus the results for a 10-marker test may look like this:
The top row, DYS (the DNA Y-chromosome Segments), are the standard designated markers and the row labelled HP1 (for Haplotype 1) are the candidate’s individual scores (that is the number of repeats of the genetic sequence at that particular marker). Note: testing such a small number of markers is not all that helpful for genealogy and much more suited to forensic matching. The more markers tested the more reliable the results. To help locate these genetic mutations, scientists have identified genetic markers with known genetic characteristics. These markers which can be found at specific locations on the chromosome are essentially places where the same pattern repeats a number of times. Since the number of repeats within these sequences is inherited, people who match at a number of markers are likely to share a common ancestor. To ensure a balanced result the markers selected include one’s known to rarely mutate and well as ones known to be prone to mutation.
Mitochondrial DNA (mtDNA) is contained in the cell itself and not the nucleus. This type of DNA is passed only by a mother to her offspring, so your mtDNA is the same as your mother's mtDNA, which is the same as her mother's mtDNA. mtDNA changes very slowly so it cannot determine close relationships as well as it can determine general relatedness. If two people have an exact match in their mtDNA, then there is a very good chance they share a common maternal ancestor, but it is hard to determine if this is a recent or remote ancestor. Y chromosome in the nuclear DNA is used to establish family ties. The Y chromosomal DNA test is only available for males, since the Y chromosome is only passed down the male line from father to son. Chemical markers on the Y chromosome create a distinctive pattern, known as a haplotype, that distinguishes one male lineage from another and shared markers can indicate relatedness between two men, although the exact degree of the relationship cannot be determined. Y chromosome testing works best if the individuals share a surname or there is some other evidence or otherwise of a possible relationship. Thus adoptees are turning to a DNA test to help them uncover their birth ancestry. Y chromosome tests will only reveal your paternal relationships. If you want to find out about the multitude of distaff lines, you will have to locate a male descendant prepared to undertake a DNA test. Thus to follow your mother’s paternal line, you need your mother’s brother or his son. To follow your father’s mother’s line you need a living male descended from one of her brothers, and so on. A mitochondrial DNA test will only reveal your specific haplogroup (that is group of similar haplotypes that share a common ancestor) that may provide information on distant family origins and ethnic backgrounds. As I said earlier, DNA testing will tell you little, in fact all it can reveal is: • if two people are related. • if two people descend from the same ancestor—it will not tell you who that ancestor was or when or where that ancestor lived. • if you are related to others with the same surname. • about your ethnic origin. An individual's DNA test provides little information on its own. Genetic genealogy differs from forensic genealogy. In forensic genealogy an exact match on two samples thought to be related is all that is required. That is a body is found and a sample is matched with a sample taken from a missing person’s known personal possessions. It may prove or disprove your family tree research. In fact unknown non-paternal incidents in your ancestry may reveal that your ancestry in a mystery and you should be prepared for this possibility. You may not welcome discovering you are not related to your siblings or close cousins! Non-paternal incidents were outlined in Newsletter 21: • an illegitimate male child passed off as mother’s brother. • an illegitimate male child within a marriage who discovers his biological father— of all of these in this list, this event cannot be detected if the father was a close relative of the woman’s husband! • a husband adopting his wife’s surname. • stepchildren adopting their stepfather's surname. • an adopted male child who takes the surname. • a foreign name altered to resemble an existing local surname. • a male purchaser of property adopting the seller’s surname. • a mis-spelling at some point that switches to a new surname entirely. • a condition for an inheritance. • an admirer or lackey taking on a superior's name. • a male hiding his identity for any number of reasons. • a male rejecting his name for personal or societal reasons. While non-paternal incidents are not helpful in all matters of family history, they do occur and in fact statistically they must occur more frequently in people with common surnames. Thus the chances of determining relationships within common surnames (and common surnames are in fact the majority of surnames) are less likely—the more common the surname, the less likely a match. The marker numbers provided in your DNA test results only begin to take on genealogical significance when you compare your results with other people and population studies. The markers become significant if the objective is to resolve an impasse in progressing ancestry, but often the barrier presented in these cases is finding willing subjects to resolve the matter. If you do not have a group of potential relatives interested in pursuing DNA testing with you, your only real option is to input your DNA test results into the many DNA databases starting to spring up on the Internet, in the hopes of finding a match with someone who has already been tested. For more on this topic refer to the website article: The DNA dilemma. |
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