Autosomal DNA Testing

The latest developments in DNA testing have significant implications for adoptees looking for birth parents and relatives. They also offer the ability to find information on other siblings of those in the direct paternal and maternal lineages.

Family Tree DNA, a US-based company, now (as of early 2010) offers the Family Finder test, which it describes as follows:

With our autosomal Family Finder test you may extend the power of genetic genealogy to all of your ancestors. Using a test of your own DNA, you can discover connections to descendants of all sixteen of your great-great-grandparents! The Family Finder test will not only open avenues for traditional research but will help you discover the hidden connections that could explain your family’s migrations.

The company refers to this test as "the next revolution" in genetic genealogy. It is identical in concept to the "Relative Finder" test offered by the company 23andMe, which came on the market in late 2009.

The idea is that SNP DNA is passed on to a child from his or her parents as a mixture of the DNA received from each of his/her parents. The DNA that has been passed on from one ancestor tends to be close together, and forms a "block" of material.

The theory is that the larger the block, the more recent the "donation" to the child. As the blocks get smaller, the common ancestor is assumed to be more remote.

So, if the results of DNA testing show a match between two individuals with respect to a fairly small block of autosomal material, the relative is likely a third or fourth cousin. If, on the other hand, the match is on a fairly large block of genetic material, those individuals are likely more closely related.

An example: my maternal aunt and I have both had our DNA tested. We share 26% of our DNA , on 46 segments.  Here is the chart of what our shared segments look like:


Matches between my maternal aunt and me.  As you can see, closer relationships have many more segments in common.

A second cousin twice removed to my aunt shares 2.49% of her genome on 11 segments; this same person, a third cousin twice removed to me, shares 1.4% of my genome on 4 different segments. He is related to us on at least three different ancestral lines, which explains why he shares so much DNA with us, given the genetic distance between us.

Here is what the chart looks like for the DNA segments he shares with us:

Matches between the above-noted cousin, my maternal aunt (green) and me (blue).  Note that 3 of the 4 segments I share with him are also shared with my aunt!


As noted above, this is a fairly large amount of sharing at this level of relationship.  That is, my aunt has another second cousin twice removed, with whom she shares .53% of her genome on two segments. I have two other third cousins once removed, a brother and sister, who share .36% on two segments, and .16% on one segment, respectively, with me.

In chart form, that is:



Maternal Aunt

Amounts of DNA Shared with Second Cousins Twice Removed

Cousin 1:  2.49%, 11 segments

Cousin 2:  0.53%, 2 segments


Me

Amount of DNA Shared with     Third Cousins Once Removed   

Cousin 1:  1.4%, 4 segments

Cousin 3:  0.36%, 2 segments

Cousin 4:  0.16%, 1 segment

(Cousins 3&4 are brother and sister)


The amount of DNA shared can vary, then, even for the same degree of relationship.

The DNA test results are based on mathematical probabilities, in determining the level of relationship the matched person is to you. When you come contact that person, you will be able to compare genealogy notes and determine exactly who the common ancestor was, and what relationship you and the match are to each other.

The degree of success, naturally, varies with how detailed, and how accurate, the two family trees are that you are comparing.

The following video from 23andMe outlines this test, although not the science behind it, in a straightforward manner:





Differences in Approach

Both the Family Finder and Relative Finder tests use the same underlying theory.

However, 23andMe deals mainly with DNA testing to discover genetic susceptibility to various medical conditions and diseases, and aims to provide medical assistance to help your body resist those medical difficulties before they get a foothold. DNA testing for genetic genealogy purposes tends to take a back seat to this goal.

Also, 23andMe tends to be very sensitive to privacy issues, as a result of the medical information it has on file.

Family Tree DNA, on the other hand, is centered on DNA testing for genealogical purposes. While 23andMe requires a new user to 'opt in' to the Relative Finder (which results in a large number of 'anonymous' matches, among whom usually are one or two of your highest matches - frustrating!), FTDNA provides an e-mail address along with the name of each person you match to.

Family Tree DNA claims they can find matches up to five generations back, while 23andMe says their matches go up to the fourth or fifth cousin level (i.e., a common ancestor up to 7 generations back!)

While most of my confirmed matches from DNA testing are within the above range, I have one match, recently made, which goes back 11 generations. However, there were some cousin marriages in that group, so some of the DNA segments got passed down a little more than they otherwise would have.



Potential Users

I am very excited about the implications of, and possible uses for, this test! As you likely have already gathered, the first group of individuals I thought of was adoptees. What a boon this would be to you! This one test would effectively render any "sealed adoption" laws irrelevant (and likely would violate a few privacy rights for birth parents along the way)!

This has proven to be the case. A large number of adopted persons have tested with the companies offering this service. One success story is recounted here.

I can also see its use in determining who the father was in an illegitimacy which occurred a few generations back, if cousins can be found whose ancestry traces back to the same time and area where the birth occurred.

I am working on one of these in my own family. Curiously, I have a large number of matches with colonial American ancestry - something about which I know nothing, as my own forebears all came to Canada from the UK in the period from 1820 - 1900. Clearly, there were other family members who migrated to the US before mine came to Canada!

This testing may be useful to African Americans in identifying relatives descended from enslaved family members who were sold to a new owner, and thereby forced to leave their family.

It could also prove very useful in linking in additional branches of a family tree, as you connect with others who are a match, and who have information about their ancestry.





How much does it Cost?

The Family Finder test from Family Tree DNA, described above, until recently was listed at US$289.  As of summer 2013, however, the price has dropped to US$99.

23andMe has experimented heavily with different pricing models over the past couple of years. Currently (as of January 2013), it has lowered its price to US$99. Their goal is to increase the size of their database to 1 million customers by the end of 2013.

Recently (in 2012), Ancestry.com has also moved into this 'game'. Many have had great success finding how people match to them there, as compared to the other two companies, as they have a well-populated family tree feature which has been there for many years.

However, at the present time, Ancestry's offering is only available to US residents. That means, of course, that the database is great for those with US colonial ancestry, but not so wonderful for those in other countries.

However, Ancestry does not provide a Chromosome Browser service, so subscribers do not know who matches whom on a particular segment of DNA. 

This is crucial for adoptees or those with non-paternal events, as finding the identity of a birth parent is dependent on finding two or more individuals who share the same segment, who have family trees, and finding the common ancestor among them.

Ancestry initially offered its service for US$199 to the general American public, and US$129 to subscribers.  As of summer 2012, it has reduced its price to US$99, plus a subscription fee payable annually. 

For further information about 23andMe's offerings, click Here.







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