Sunday, March 21, 2010

Ancestral DNA and African-American Research

Part II  - Markers and Databases - Points to Consider

For me personally, the one thing, knowing exactly where your ancestors came from in Africa, that drives most African American researchers to do DNA, was never the driving force behind my doing DNA testing. What can I say I’ve always marched to the beat of my own drummer. For me, DNA testing was just another tool to use in in hopefully breaking down brick walls on this side of the Atlantic Ocean as well as reconnecting with lost kin.

These two thoughts, the need to know the exact locale from whence your Ancestors came and the need to break down brick walls and reconnect with lost kin are not incompatible with each other but may alter how you approach your research on ancestral DNA and which company to test with. In some cases, you may need to test with more than one company to obtain your goals.

Breaking through Brick Walls with DNA

When used as a tool to help break through brick walls, I think it’s important to know the size of the testing company’s database and to know how many STR markers and which ones are tested on a yDNA test and how many regions are tested on the mtDNA testing.

For yDNA testing, there are two types of markers, STR Markers and SNP markers. STR markers provide information on the personal Haplotype and SNP markers provide information on the Haplogroup. Put another way, STR markers provide information on your more recent ancestry and SNP markers, which mutate at a slower rate, provide information on your deep ancestry.

Understanding Markers

Depending on the testing company, you can order anywhere from a 9 to 91 STR marker test. A breakdown of the benefits of adding additional marker, beyond 12, to your testing is as follows:

  • 12 markers – Mainly used for anthropology projects, 12 marker testing does not provide enough information to provide conclusive results for genealogical purposes. An exact match at 12 markers means there is a 50% probability of having a common ancestor within the past 14 generations.

  • 25 markers – An exact match at 25 markers means there is a 50% chance that you share a common ancestor within the past 7 generations.

  • 37 markers – An exact match at 37 markers means there is a 50% chance that you share a common ancestor within the past 5 generations.

Some companies also offer further testing on the SNP markers providing what is known as subclade testing. This type of testing confirms the haplogroup that is predicted by STR (haplotype) marker testing.

mtDNA testing follows along a similar protocol with its coding regions. There are 3 coding regions, HVR1, HVR2, and HVR3. The majority of companies test two of the three coding regions; however, some only offer the HVR1 region. The information provided by adding additional tests regions is also similar to that of adding addition markers in yDNA testing.

I equate the adding of additional markers to starting with the ocean (12 markers) and narrowing it down to a single drop of water (67 markers). Do you need to add all the additional markers? No, but I think for genealogical purposes, you definitely need to go beyond just 12. Depending on the company you decide to test with, you can start with say 25 or 37 markers and later add more, if needed.

Database Size

If trying to break through a brick wall, the larger the database, the greater the possibility of your finding a possible DNA connection that may assist in helping that brick wall come tumbling down.

In this regard, it appears that Family Tree DNA has become the standard by which all others are judged as they have what seems to be the largest database. Please note that while I have tested with Family Tree DNA, this is not to say that you should or have to test with Family Tree DNA. This is simply provided as information for your research on Ancestral DNA.

Also, keep in mind that although DNA testing for genealogical purposes has been around for a few years now, it’s still somewhat of a novelty and is still somewhat expensive. The number of descendants of a given line researching is small and those that are doing DNA testing is probably even smaller. Therefore, while you may not get an exact match, you may still get a lead. Remember when it comes to breaking through the walls, it's a tool to be used in conjuntion with traditional research methods.

Determining Place of Origin through DNA

As determining place of origin on the continent of Africa is the driving force behind most African American researchers doing DNA testing, the size of the database and number of markers don’t play as significant a role as the type of database used by the testing company. Therefore, databases that are specifically geared toward Africa are very important.

The company most noted and probably the standard in this area is African Ancestry. If you have tested with another company, African Ancestry can take those results and interpret them to provide you with your present day African country of origin. In order to do this, your previous mtDNA results need to indicate that you are in Haplogroup L and your previous yDNA results need to indicate that you belong to Haplogroup A, B, or E. There is still a fee for this service but you do not have to submit another sample.

To Be Continued

1 comment:

  1. very good articles my friend. At least I can understand your analogy. As for my MTDNA I regret I can't go to African Ancestry.(Hap I) and my male cousin can't either.(YDna R1a). It is what it is though and I am still proud.These are on my maternal side. But my paternal side is a different story. E1A1,E1B1 for YDNA and L1 for MTDNA. Now to get the funds to go further lol


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