DNA – A New Alphabet Soup for Winter Research
Letters and numbers, today we are coded and categorized everywhere we go.
Although this seems like a recent phenomenon it has actually been happening for eons.
Our DNA is the expression of our unique genetic code.
Although this code is 99% identical from person to person it is that 1% that makes each person unique and that is what is revealed in DNA testing.
DNA is often represented as a spiraling ladder with four colors (red yellow blue and green) and four letters (CTGA).
Each part of that spiral is considered a MARKER which is a term you will see often in DNA testing for Genealogy purposes.
Markers are coded and categorized to create information that is then compared to other people DNA.
But before we open the can of genetic alphabet soup let’s consider why you are testing and what it will tell you.
There are three tests most commonly used for genealogical purposes.
Unlike the DNA tests seen on CSI the goal is not necessarily to find an exact match but rather a match that is close enough to prove a connection.
Each of these tests only gives a certain kind of information so it is important to understand what these tests are and what they can tell you.
Autosomal DNA (atDNA) This test can be used to determine recent genealogical connections or ethnic ancestry.
It is a test for the DNA that all people share and can be analyzed two different ways.
Recent Genealogical Connections – The test looks for repeated patterns (STR markers) in the DNA sequence.
Since half of each parent’s DNA is given to a child, that sequence of DNA or marker will be represented in the child’s DNA.
A child carries the markers of all of its ancestors with the most recent ancestors in the highest frequencies.
This is haploblock matching; a process that counts the number and size of matching runs of DNA from one point to another.
It then computes the likely number of generations between two people.
If there is a match at this point in testing you will know someone is related and you might even be able to determine how many generations back but it may or may not tell you who that common ancestor is.
Ethnic Genealogical Connections – This uses SNP which are single-nucleotide polymorphisms to look at bio-geographical analysis as these SNP’s are then compared to known frequencies in certain populations.
This is a good way to find out if there really is an Indian princess or Spanish Pirate in your heritage.
Mitochondrial DNA (mtDNA) This test is used to look at the DNA passed from mother to child.
It – both mother and mitochondrial start with the letter “M” so that makes it a little easier to remember.
This type of DNA changes very infrequently and the results are shown as a series of numbers and letters that then are categorized into a Haplogroup.
Exact matches can point to recent shared ancestors.
Less than exact matches (due to generational distance and mutation) can give a specific reference to a geographic region.
In theory, a line can be traced back many generations to a specific woman (ie. Eve) however the lack of lineage information for women (surname changes in each generation) make specific identification difficult.
This was the type of DNA test used to identify the remains of King Richard III found under a parking lot in Leicester England.
The match was found to a known descendant alive today which proved that those were royal bones—although it brought up many questions also.
Y chromosome (Y-DNA) This is the DNA passed on from father to son on the Y chromosome and is often referred to as patrilineal or male line DNA.
Since only men have Y chromosomes this test can only be done on men.
The Y chromosome DNA changes only through mutation so two people who share the same sequence on their Y chromosome exactly share a common male ancestor.
Since this relationship passes from father to son it is the genetic equivalent of a last name or lineage. When Y-DNA is tested those results can become part of a Surname project.
Analysis of the common features of the Y-DNA can show if two lines of a family that share a surname are actually related. Minor differences in the Y-DNA can show how far back the common ancestor is likely to have lived.
In the recent PBS series “Finding your Roots” with Henry Louis Gates Jr., this test was often used to determine the most likely candidate for the father of an otherwise “fatherless” slave.
It was also handy in determining the source of the European component of many African American’s heritage.
If this cursory explanation of DNA and how it can be used for genealogical research intrigues you, I suggest you view the 10th episode of “Season 2 of Finding Your Roots.”
The principles outlined above are discussed in detail through three case studies and an interesting and informative way.
DNA tests and results are one way to enhance your genealogical search or even begin to break down a brick wall.
It is only through the combination of the genealogical research of written records and the analysis of the DNA test results that more information will be gained.
It is a research path that can take some surprising twists and turns so approach it with an open mind-your DNA may reveal a different lineage then you anticipated.