Monday, October 31, 2011

Investigating Another Genealogical Theory Using DNA - Ratekin

Recently a researcher of the surname Ratekin contacted me, explaining that his brother had seen one of my postings about my Ratekin ancestors. I descend from Patrick David Ratekin (c.1740-1804) and he descends from his presumed brother John Ratekin (c.1732-c.1806). Although there is circumstantial evidence supporting the belief that Patrick and John were brothers, to my knowledge no proof has been found. Both of these Ratekin men lived first in Berks County, Pennsylvania, then moved to Loudon County, Virginia and finally settled in Campbell County, Virginia. If they were indeed brothers, then this Ratekin Cousin and I would be 7th cousins.

I was excited to find out that he had also tested his DNA at 23andMe. So we "shared genomes" match! Unfortunately, we weren't able to confirm the relationship between us using DNA, however this does not disprove the theory that these two were brothers. Why is this? It is because the odds of 7th cousins having enough shared DNA to be detected by 23andMe's ancestry tools are extremely low - well under five percent.

Autosomal DNA is a very useful tool for proving relationships, however for relatives beyond second cousins, the lack of shared DNA cannot disprove a familial relationship. It is estimated that even an authentic 3rd cousin relationship will not be detected by 23andMe's ancestry tools about ten percent of the time. This is because of the random nature of autosomal DNA inheritance. With each successive generation, the DNA is spliced, mixed up and recombined. As this happens it is possible, although rare, for the DNA of a great great grandparent to completely disappear from our genome (at least as far as the current tools are concerned). By the time you reach a common ancestor as distant as a sixth great grandfather, the chances are good that all detectable traces of that ancestor have disappeared from your DNA. This does not mean that it is impossible to discover an authentic 7th cousin, or even one more distant, at 23andMe or on FTDNA's Family Finder. (In fact, I have done so.) Since all of our DNA necessarily must come from our ancestors, it is not surprising that we can still find traces of some of the more distant ones. Unfortunately, a majority of the time this will not be possible.

So, this time the investigation did not provide us with any useful data, but I am looking forward to the next opportunity for discovery.

Investigating a Long-Held Genealogical Theory Using DNA Evidence - Purdy

About a decade ago when I started my family history research in earnest, I was assisted by an extremely talented genealogist by the name of Karin Corbeil. I was amazed at her generosity and the amount of time and care that she invested in researching my family line. At the time, I couldn't understand why someone would volunteer to research a family that wasn't even their own and ask for nothing in return. That was before I came to know the community of genealogists and witnessed this kind of generosity over and over again.

Karin's husband descends from Nancy Purdy (1797-1878) and I descend from Daniel Purdy (1817-1897). Daniel is one of my most recent brickwalls. Karin had long theorized that both Nancy and Daniel were grandchildren of Joseph Purdy (c.1736-1818) whose family is found in 1803 in Haldimand Township, Ontario, Canada. Joseph Purdy was the son of Obadiah Purdy and Phoebe Underhill. If her theory is correct this would make her husband and I sixth cousins.

To all of our benefit, Karin has now ventured into the world of genetic genealogy and, with a mind like hers, she is extremely well suited to the endeavor. While scanning her husband's Relative Finder matches on, she came across an anonymous match with familiar ancestral surnames listed (not Purdy). Due to her extensive work on the Purdy family trees, with only four surnames to go on, Karin was able to make an educated guess as to who the person was behind 23andMe's shield of anonymity! She then asked me if I also had this individual on my list of matches. I didn't, but I did find him in my paternal aunt's and uncle's Relative Finder by searching on one of the listed surnames. Since he hadn't answered her initial invitation through 23andMe, Karin tracked down an email address and sent a message to the suspected person behind the match. Sure enough, she was correct and, even better, he was willing to "share genomes" with both Karin and I to determine more details about our match.

Karin's husband and this individual, who are 4th cousins through their Purdy ancestral lines, share .35% of their DNA and were correctly predicted to be 4th cousins by 23andMe. Interestingly, this Purdy Cousin also matches my aunt and uncle, who would be his 5th cousins once removed if Karin's theory is correct, on .14% of their DNA and was predicted to be a 5th cousin. My sisters and myself, who would be his sixth cousins, do not show a match with him at all on 23andMe.

Purdy Cousin compared to me, my uncle (green) and my aunt (light blue)

We also investigated our matches on to determine if there might be some smaller matches that fell just below 23andMe's matching threshold. Since my father was tested at FTDNA instead of 23andMe, I was also able to compare his DNA to that of our Purdy Cousin using Gedmatch's tools.

On Gedmatch the following matching stretches of DNA were detected with our Purdy Cousin:

With Karin's Husband:
Chr Start Location End Location  Centimorgans (cM)  SNPs
1     88,186,177        94,337,025          5.6                   2,240
1     94,337,035       114,454,559        19.6                  7,219

With Me:
Chr Start Location  End Location Centimorgans (cM)   SNPs
1       5,314,984       7,050,643            3.6                        503
8     136,313,206    138,665,940         3.9                        554
9     127,867,126    130,999,928         4.4                        747
12    24,589,880      26,489,079          3.3                        689
12   114,422,485     116,042,182        3.4                        516

With My Uncle:
Chr Start Location   End Location Centimorgans (cM)  SNPs
1      206,237,168      215,353,110       12.3                   2,045

With My Dad:
Chr Start Location   End Location Centimorgans (cM)  SNPs
1        5,044,926        7,029,550           4.0                      624
3       29,876,878      31,804,154          3.0                      587
10     73,415,605      78,397,973          3.7                      902
16     53,357,205      55,155,137          3.4                      576
16     78,611,267      80,033,433          3.5                      571

With My Aunt:
Chr Start Location  End Location  Centimorgans (cM)  SNPs
1       206,246,175    215,354,364    12.3                       3,487
19       8,636,038        11,088,559     5.6                          809

Many of these segments are too small to be meaningful, especially the matches that I show on Chromosomes #8, 9 and 12 since they are not detected in my father's DNA. However, when looking at this data as a whole, it is apparent that there truly is a familial relationship between these individuals. Although we cannot be absolutely certain that the shared DNA that has been detected between them is from our Purdy ancestral lines, I feel comfortable that this data combined with Karin's many years of solid research shows very strong evidence in support of this conclusion. Karin writes that this is "... a huge breakthrough in the genealogical community for Purdy researchers. For many years now, I and a number of family researchers and historians have been trying to connect Nancy Purdy (wife of Harnden Eddy) to other Purdys in Ontario, Canada."  In time and with more Purdy descendants in the database, I believe that we will be able to determine beyond a reasonable doubt if this DNA is indeed inherited from our presumed common ancestor Joseph Purdy.

On a side note, I recently discovered that Karin is adopted and searching for her birth family, which is astounding considering her genealogical prowess! She was born as Carol Lee Foley on July 22, 1945 in Brooklyn, New York. If anyone has any information that might help Karin find her birth family, please contact me and I will pass it on to her or visit her new blog. I am quite confident that with her research skills and the newly added valuable tool of DNA to her toolbox, Karin will soon solve this mystery. The family that she finds will be very lucky to have her. I wish her and all adoptees success in their searches. Everyone deserves to know who they are and, in this era of personal genomics, it is finally becoming possible.

[Update - Karin Corbeil has reunited with her birth family, in part, thanks to DNA testing.]

Sunday, October 23, 2011

Known Relative Studies at 23andMe: Second Cousin Comparisons, Allen Great Grandparents

I am very pleased to report that I have received the results for my Allen second cousin's DNA test. This is exciting because he shares the only set of great grandparents from whom I have had no genetic data up to this point. Our common ancestors are our great grandparents George Henry Allen (1880-1965) and Fredrikka Herstad Allen (1871-1953). They were both immigrants to the United States around the turn of the 20th Century. George was from Australia and Fredrikka was from Norway. They met in San Francisco and married shortly after the Great Quake of 1906. I descend on my paternal side through their daughter Wanda and this cousin descends maternally through their daughter Flora.

I was surprised to see how much DNA we all share with our Allen Cousin. My family shares more DNA with him, across the board, than we have with any of the other cousins in my "Second Cousin Studies". My sisters and I share well above the expected percentage for a second cousin of 3.125% of DNA in common with our Allen Cousin: 4.45%, 4.27% and 3.64%.

Three sisters compared to their second cousin

As usual, you can see the unique pattern of inheritance, with each sister sharing different portions of their genome with this cousin (shared DNA with each illustrated by the three different colors).  You an click on the chart to get a closer look. Chromosome #6 is especially interesting because we all share a majority of that chromosome with our cousin, meaning that for all three of us siblings the Chromosome #6 that we inherited from our father was inherited almost exclusively from his mother Wanda and, in turn, his Allen grandparents.  At the same time, we can be confident that our Allen cousin inherited his maternal Chromosome #6 almost entirely from his grandmother Flora and her parents George and Fredrikka. In my experience, it is a bit unusual to see such a large portion of DNA inherited intact over multiple generations such as this, especially by all tested descendants. Conversely, you can see that none of us have inherited any common DNA on Chromosomes #4, 5, 8, 10, 11, 15, 21, 22 or X. That doesn't mean that we didn't inherit any DNA from our Allen great grandparents on those chromosomes, only that we cannot detect any in this comparison due to the lack of shared DNA in those areas. In order to be able to detect the common ancestors' DNA, BOTH sides must inherit the same genetic blocks. If we tested this cousin's siblings, we would, almost certainly, be able to pinpoint more DNA from the Allens in myself and in my close family members.

Next I compared our Allen Cousin against three of his second cousins once removed, children of the sisters in the first chart.

Allen Cousin compared to three 2nd cousins once removed

As you can see they retained much of the common DNA on Chromosome #6, but lost many of the other blocks of DNA that their mothers had in common with the Allen Cousin in the first chart. Overall, they were still on the high sharing side with 2.29%, 2.02% and 1.81% instead of the expected average percentage of 1.563% between second cousins once removed. Below is a closer look at the autosomal DNA inheritance pattern of one of the sisters and her offspring compared to our Allen Cousin.

Our Allen Cousin compared to one sister and her offspring

You can see that most of the DNA in common was retained on Chromosomes #2, 6, 13 and 17, while much was lost on Chromosomes #3, 9, 12, 16 and 18.

Lastly, I compared my aunt and uncle to this cousin. Although they are first cousins once removed, they share so much DNA with him that they would appear to be full first cousins. In fact, that is what 23andMe predicted their relationship to be with 11.8% and 11.1% of their DNA in common. Since first cousins are expected to share an average of 12.5% of their DNA and first cousins once removed are only expected to share approximately 6.25% of their DNA, you can clearly see why 23andMe's software reached this erroneous conclusion.

The chart below illustrates my cousin's DNA in common with my uncle, my aunt and myself.

Allen Cousin compared to two 1st cousins once removed and a 2nd cousin

In contrast to my sisters and I, who are one generation further removed, my aunt and uncle share DNA on almost every chromosome with him. Since I do not have my deceased father's DNA sample at 23andMe, I added myself to the chart to demonstrate the different inheritance patterns of each of the siblings. The areas where I alone share with him (light blue) shows that my father inherited those sections in common with our Allen Cousin, and his siblings did not (dark blue and light green). For instance on Chromosome #3, my father inherited a longer stretch of DNA in common with his Allen Cousin than his siblings did. On the other hand, my father's sister inherited stretches of DNA in common with our cousin on Chromosomes #4 and #22 that we did not. Look again at Chromosome #6. It is interesting to see that my father's siblings also inherited large blocks of DNA in common with our cousin on that chromosomes, however they are not the exact same blocks that my father inherited, which can be seen clearly in the earlier chart from the three sisters' inheritance. My aunt did not inherit the same DNA as her cousin in the center part of her Chromosome #6, while her brothers did.

I love being able to actually "see" DNA from my Allen great grandparents.

George and Fredrikka Allen

Now that I have second cousins from all of my ancestral lines, my next step is to combine the data from each of my second cousin studies to begin to map out my great grandparent's DNA on my chromosomes and those of my close family. Isn't that exciting?

Thursday, October 6, 2011 Venturing into Autosomal DNA Testing?

Last night I was able to register for a "free upgrade" to what appears to be a new autosomal DNA service offered by This offer is available only to current subscribers who have had a DNA test through Ancestry DNA in the past. It is being offered to the first 2000 who register. You must be logged into your account and use this link.Details are scarce. It was reported on one of the DNA mailing lists that 700,000 SNPs will be tested, similar to the autosomal tests currently being offered by 23andMe and FTDNA. I have been unable to confirm this information. This was the only information provided when I signed up:

Another customer reports this information at the same link when they signed up:

What You'll Get
Your Genetic Ethnicity
By testing over 700,000 of your DNA markers, you'll see the mix of ethnicities you have in your genes and how they relate to your family tree.
More comprehensive DNA matching
Find more and closer relatives, overcome brick walls, confirm relationships and find common ancestors.
Enhanced, simple web site tools
Use your AncestryDNA results and the power of to make new discoveries and solve family mysteries.
Early access - Preview the new service and give feedback that will ultimately enhance this experience for everyone.
What are the requirements to receive the free offer?
To redeem this offer, you must be a current subscriber, must have submitted DNA to and must be one of the first 2,000 users to fill out the registration form before Midnight ET on October 18, 2011
First results are expected in early 2012.

In response to an inquiry in this regard, customer service responded only, "Details...are still being worked out."

In the last few weeks there have been some whispers about the possibility of offering autosomal DNA testing due to some recent job postings. For example, on September 13th, the following was posted on Google+: "™s new DNA group in San Francisco is in need of a PhD with a track record of productive research in statistical and human population genetics and genotyping to lead a group of computational biologists."

In part, this job listing reads: 
The right person will be using a huge dataset of information from all over the world, developing methods and experimental design to improve results in genotyping data to inform pedigrees. This is not (yet) for medical research and, as such, is not regulated by the FDA. There is every opportunity to become one of the thought leaders in this field... is the world's largest online resource for family history...Job Description: is seeking a talented population geneticist to join the team. We are mounting a major effort to use genomics to shed light on human diversity, origins and relatedness. The successful candidate will join our efforts to develop and apply analysis pipelines to exploit genotyping data in order to provide information about countries of origin, relatedness and apply genetic information to the construction of human pedigrees. In this position, you will develop, implement and improve methods to use SNP data to provide information on relatedness and genetic origins of humans. You will work closely with other biologists in analyzing data as well as with members of the product development team. This position offers an exciting opportunity to apply cutting edge computational approaches to an unprecedented, large-scale set of pedigreed human genome data. Characteristic duties will include: • Develop, benchmark and implement data analysis pipelines for SNP genotyping data • Evaluate significance of results and recommend changes in experimental design to improve results • Develop, benchmark and implement methods to use genotyping data to inform pedigrees. • Identify new experimental and/or analytic approaches that will improve the outcome of the study • Manage collaborations with laboratory and informatics staff • Successfully communicate scientific concepts to a diverse community of scientists and laypeople Key Responsibilities / Performance Requirements: • Doctorate degree in statistical genetics, population genetics, statistics or a related field. • Candidates should have a track record of productive research in statistical and population genetics • Experience in human population genetics and genotyping • Ability to manipulate large data sets • Programming skills in UNIX/LINUX operating systems, and fluency in standard genetic analytic software (such as R/Bioconductor, EIGENSOFT, MACH, PLINK, ADMIXMAP) • Experience in molecular biology and high-throughput environments would be a significant advantage. • Excellent organizational skills • Superior oral and written English communication skills required. • Must be able to manage multiple simultaneous long-term projects while meeting frequent project deadlines in a fast-paced environment. • Must be able to translate high-level biological questions into concrete tasks.

Sounds exciting! (Note the part about not yet for medical research!) The idea of DNA testing in conjunction with readily searchable/matchable family trees is extremely promising if implemented correctly. In the past,'s DNA testing division has not had the broad customer support network to make it a viable competitor for companies like FTDNA. It remains to be seen if that will change in regard to this new venture. I, for one, will keep an open mind.

I will post updates as I get them on this very interesting development in the world of genetic genealogy.

*Update - One customer reported that the offer was no longer available when she clicked through the link, so they may have already reached the 2000 limit.

Related Posts:
More Details on's New Autosomal DNA Test Offering
Update on the New Autosomal DNA Test from DNA testing - Get the first look here.