Friday, July 27, 2007

DNA Genealogy

Author: Curt Whitesides

The next time you are watching your favorite CSI TV show or a particular movie and stumble into the fascinating world of DNA, you might be surprised to know that our DNA can do more than identify a suspect or victim at a crime scene. In fact, DNA is now being used to identify ancestors in the new and exciting field of DNA Genealogy.

DNA Genealogy takes traditional genealogy and applies genetics to it. DNA Genealogy involves the use of genealogical DNA testing to determine the level of genetic relationship between two individuals (Genealogical 2005). DNA, deoxyribonucleic acid, is used in the process because of its unique nature and the fact that it is passed down from one generation to the next. In the passing, some parts of the DNA remain almost completely unchanged, while other parts change dramatically. This property allows for the identification of certain consistencies between generations and provides the ability to identify genetic relationships.

There are two types of DNA tests available for testing

DNA Genealogy : Mitochondrial DNA (mtDNA) and Y-chromosome DNA tests.

Mitochondrial DNA (mtDNA) is found in the cytoplasm of the cell instead of in the nucleus as is Y-chromosome (Tracing 2003). mtDNA is passed by a mother to both her male and female children without any additions or mixing from the father. Therefore, your mtDNA is the same as your mother's mtDNA. mtDNA is different in nature compared to Y-DNA. It changes slowly making it more difficult to determine close relationships and easier to determine relatedness. If two people have the same mtDNA, there is a very good chance that they also share a common maternal ancestor. Unfortunately, it is difficult to determine if that common maternal ancestor was recent or instead lived hundreds of years ago.

Y-chromosome tests have been used more and more recently to determine

DNA Genealogy . The Y-DNA tests are only available for males, because the Y-chromosome is only passed down along the paternal line from father to son. There are tiny chemical markers on the Y-chromosome that create a unique pattern. This pattern of markers is what is called a haplotype. A haplotype is used to determine one male lineage from another. This type of testing is often used to determine if two individuals who have the same surname share a common ancestor.

One of the early beginnings of DNA Genealogy was a study published by Bryan Sykes in 2000 (Sykes and Irven 2000) that used DNA Genealogy (Y-chromosome markers) along with surname studies to determine relatedness. The study compared 48 men with the same surname of Sykes from the regions of England and analyzed four Short Tandem Repeats (STRs) on their Y-chromosome: DYS19, DYS390, DYS391, and DYS393. The study found that of the 48 men tested, 21 had the same core haplotype and many others were only one mutational step away from the core haplotype. Skypes interpreted these results to reveal a common origin from an ancestor who lived some 700 years ago (Butler 2005).

Since its early beginnings,

DNA Genealogy has come a long way and has grown rapidly. DNA Genealogy continues to increase in popularity as the price of tests becomes much more affordable and the number of markers and clarity of the tests become greater. Additionally, DNA collection techniques make it a very simple and pain-free process.

Sources

Butler J. (2005) Forensic DNA Typing; Biology, Technology, and Genetics of STR Markers, 74, 231-232.

Genealogical DNA test. (2005, December 7). Wikipedia, The Free Encyclopedia. Retrieved 21:52, December 8, 2005 from http://en.wikipedia.org/w/index.php?title=Genealogical_DNA_test&o ldid=30489865.

Sykes, B. and Irven, C. (2000) American Journal of Human Genetics, 66, 1417-1419.

Tracing Your Ancestry Through DNA (2003) Genealogy.com. http://genealogy.about.com/cs/geneticgenealogy/a/dna_tests.htm

About the author: Relative Genetics , a leading provider of

DNA Genealogy , specializes in testing services on both the paternal and maternal lines, extended and nuclear family relationships, and Ancestral Origins TM analysis including both deep ancestry and ethnic heritage analysis.

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