10 September 2008

Understanding the Benefits of DNA Testing for Genealogy - Part 3: Choosing a DNA Test


There are four types of DNA tests, but only first two listed here really helps with genealogy. The third one helps with one’s more ancient ancestry, if your interest lies there. The last is too unpredictable to be a good indicator of genealogical relationships.

1. Y-chromosome DNA (Ydna). This test can help trace the paternal lines from father to son to grandson. Only males can test as one must have a Y-chromosome. This test can determine or exclude Native American or African ancestry by comparing haplotypes or tester can order a SNP to confirm the haplogroup

2. Mitochondrial DNA (mtDNA). This test can help trace maternal lines – mother to daughter to granddaughter and can be used for genealogical purposes through careful research. It requires good genealogy research and the location of qualified female descendents for success. Mitochondrial DNA can determine or exclude African & Native American ancestry. It is much more useful anthropologically. Successes, when they happen, are huge! This testing can associate men or women to one of the "daughters of Eve"

3. Single Nucleotide Polymorphism (SNP). A Variation that occurs when a single nucleotide (A,T,C,or G) in the genome sequence is altered. It occurs in both Ydna and mtDNA and happens only once for the particular marker. SNPs are used to categorize haplotypes for Phylogenetic Trees.

4. Autosomal DNA (atDNA). This type of markers is in the coding or Re-combining region of the genome. It is the random combination of all genetic information passed down to us from all our blood-line ancestors. At conception we received genetic data from both of our parents and it recombines to be the unique you that you are. This type of DNA determines our unique identity and appearance and makes us similar to our parents and siblings. This type of testing is used for the typical paternity tests and individual identity tests in forensic testing (Combined DNA Index System or CODIS).

........It does not aid genealogy research since there is no continuity over time. Testing results given in percentages for some ethnic groups. Connecting to an African or Native American tribe is based on the size of a company’s database which changes regularly. Databases change over time, thus so does the results based on autosomal testing. That is to say, if you tested your autosomal markers to determine what percentage of what ethnic group you are, because these markers recombine with every conception, your sibling would have different percentages quite often. Because of the sizes of the database, if you tested now and tested again in five or so years, your percentages would be different as might be the particular tribe some companies feel they can attribute to your markers. In time when the databases are much larger and the paper trails are more accurate as to which tribes are connected with specific DNA results, Autosomal testing will be more accurate than it is now, but not as accurate in predicting solid information as either the Ydna, the mtDNA, or the SNP.

Who can test and how?

1. Males can test their Ydna to get their father’s all male line
2. Males can test their mother’s mtDNA to get their mother’s all female line
3. Females can only test their mtDNA to get their mother’s all female line

How can other lines of my lineage be tested?

1. Choose the person for which you wish to obtain DNA
2. Put that person as Number 1 on a Pedigree Chart
3. Find the all male or all female line
4. Do “Reverse Genealogy”

For more information on DNA Testing and explanations of all the terms, consult the following tutorials and books. There many more books and online resources, but these are the most understandable by the novice. The books below can be found for under $10. Some may be in your library. For some other excellent books, please see the list on this Blog.

Click on TUTORIALS on the right

World Families Net - many topics

Genetics & Genealogy - An Introduction
Genetic Genealogy DNA Testing Dictionary
Genetic Genealogy Glossary

The Genetic Genealogist...a blog to follow
Free booklet from Blain T. Bettineger, Ph.D. (Click on icon to the right)

Wonderful beginners book on Genetic Genealogy:

....Family History in the Genes by Chris Pomery

Also see if you can find in your library or used book store:

....Trace Your Roots with DNA by Megan Smolenyak and Ann Turner

©Aulicino, 31 Aug 2008

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