The Genetic Genealogist

Last week I wrote about the results of my Family Finder autosomal DNA test by Family Tree DNA (see “A Review of Family Tree DNA’s Family Finder – Part I“).  The Family Finder test uses a whole-genome SNP scan to find stretches of DNA shared by two individuals, thus identifying your genetic cousins (and will soon include the Population Finder analysis of admixture percentages).  I currently have over 33 genetic cousins in Family Finder, and I’m working with them to identify our common ancestor(s).

The Affymetrix microarray chip used by FTDNA includes over 500,000 pairs of SNPs located on the X chromosome and the autosomes (no Y chromosome SNPs).  Via SNPedia:

FamilyTreeDNA uses an Affymetrix Axiom CEU microarray chip with 3,269 SNPs removed (563,800 SNPs reported) for autosomal and X (but not Y or mitochondrial) ancestry testing for $289. Other sources have cited 548011 snps. This platform tests 1871 of the 12442 snps in SNPedia.

FTDNA states that the Family Finder test is not intended to be medical.  From the FTDNA FAQ:

Question: Is the Family Finder test medical?

Answer: No, it is not.

This is entirely accurate of course; FTDNA does not analyze the test results for health, traits, or other medically-relevant information, and does not provide the user with any medical information or analysis tools that might reveal medical information.

However, when DNA is involved there is almost never any such thing as a completely non-medical test.  It’s often impossible, at any given point in time, to know which of an individual’s SNPs might be affiliated – remotely or closely – with a medical state or condition.  Ann Turner recently wrote the following at the Rootsweb GENEALOGY-DNA mailing list in response to another individual’s question:

Question:  “I am wondering if FTDNA really left out the genes and just lists the intergenic areas?”  Answer:  “No, the claim was that they scrubbed medically significant SNPs.  They still include over 1600 SNPs with entries in SNPedia, which would have some phenotype implications, according to an analysis posted at DNA-Forums: http://tinyurl.com/27slbj8.”

Indeed, as of August 3rd, 2010, there are 12,442 SNPs in SNPedia, of which a total of 1,871 are tested by Family Tree DNA’s Family Finder test.

Promethease Analysis

I was curious as to what information my Family Finder results might contain, so I ran my results through Promethease, a free software tool used to analyze whole-genome SNP scan results.  From the Promethease website:

“Promethease is a tool to build a report based on SNPedia [an impressive database of annotated SNPs] and a file of genotypes [i.e., your Family Finder results]. Customers of testing services (23andMe, deCODEme, Navigenics, …) can use it to learn more about their DNA. It can also pool the data from multiple testing services. The program runs for approximately 3 hours. An optional $2 payment per run unlocks extra features and reduces runtime to approximately 5 minutes.”

Similar to several of the other autosomal SNP scan testing companies, Family Tree DNA allows the customer to download their own DNA testing results.  Autosomal results and X-chromosome results are separately downloaded as compressed files which can then be extracted for analysis.  After downloading and installing Promethease, I ran the program using just my Family Finder results (after paying the $2 for a faster runtime.  I’m impatient.).

Promethease was  indeed able to analyze my Family Finder results and returned a report that included 1881 annotated genotypes. Here, for example, is a screenshot from my results (click to embiggen):

In addition to the “most interesting snps” category, there are categories for “medicines”, “medical conditions” (below), and others.  After clicking on “more” for each category, I receive more information about those annotated SNPs.  To get an idea of what the full results look like, there are a number of people who have shared their real promethease reports.

Promethease also lets you upload your results from different companies, so I also analyzed my Family Finder results together with the results of my 23andMe test.  Since there isn’t much overlap between the SNPs in the FTDNA test and the SNPs in the 23andMe test (see this ISOGG Wiki page for more information about FTDNA’s testing versus 23andMe’s testing, for example), I was able to extract information about 7691 of my personal genotypes using the SNPedia database (compared to 1881 genotypes with my Family Finder results alone).  Thus it appears that the 23andMe results are more likely to contain SNPs that are annotated in SNPedia.  This isn’t surprising considering that, according to reports, FTDNA designed their chip to contain fewer annotated SNPs.

My Results

Since I have taken whole-genome tests before and was familiar with both testing and the interpretation of results, my report was not surprising.  Indeed, I was already aware of my increased risk of type-2 diabetes (see Personalized Genomics: A Very Personal Post ), as well as the fact that I’m “probably light-skinned” (see e.g., my bathroom mirror).  However, it might not be clear to those taking these tests that the results contain a large amount of medically-relevant information.  This can be problematic when considering the fact that Family Finder test-takers might share or reveal their data with other people.  Indeed, even knowledge that you share a region of DNA with another person can reveal medically-relevant information that the two people share in that region.

On the other hand, this ability to apply Family Finder results to information in SNPedia will be of great interest to a number of test-takers who are interested in this type of genetic analysis.  This type of “do-it-yourself biology” is becoming more and more popular everyday.  Although there is still much debate regarding the utility of such information, exploring one’s genome can be highly interesting, informative, and interesting (and, to date, no one has adequately shown that exploring one’s genetic data is harmful for anything other than a tiny minority of people).

Conclusions

In conclusion, it is important for consumers to realize that ALL genomic information has the potential to reveal medically-relevant information (even Y-DNA and mtDNA results can include health information, for example).  By no means, however, am I suggesting that people should forgo whole-genome SNP scans, or that governmental regulation is needed.  Instead, I think it is vital that consumers understand the testing process and possible outcomes before testing, and I fully believe that it is the consumer, not the government, who should decided whether the consumer should or can undergo testing.

Indeed, rather than expend thousands of dollars in hearings, [faulty] investigations, and regulation, the government could use that money to fund programs that educate the population about genetics and DTC testing.  After all, we are entering a future that will involve our personal genomes in many aspects of our lives.

I’m interested to hear your thoughts on this subject, so please feel free to leave a comment below.

(Disclaimer: Please note that I received my Family Finder test without charge from Family Tree DNA for purposes of this review.  Regardless, I have attempted to review this product as honestly and as objectively as possible in order to provide valuable information about Family Finder to my readers.  I am also a consultant for Pathway Genomics.)

Today at noon, the American Society of Human Genetics lifted an embargo on “Inferring Genetic Ancestry: Opportunities, Challenges, and Implications (pdf),” which will be published in the May 14^th issue of the American Journal of Human Genetics.

This paper is a follow-up to a 2008 paper called the “ASHG Ancestry Testing Statement and Recommendations” in which a committee from the ASHG addressed concerns about the claims made by genetic ancestry testing companies.  I wrote an article here on the blog at the time – The ASHG Ancestry Testing Statement and Recommendations – that highlighted a number of concerns I had about the statement and the recommendations.

When I wrote the November 13, 2008 blog post, I began by pointing out my personal positions, which have largely remained unchanged in the intervening 1.5 years:

• After years of experience in this field, I am a proponent of genetic genealogy testing, a scientific endeavor that has been utilized by more than 800,000 customers.

• I believe that education, not more government regulation, is the most efficient and appropriate answer to the issues raised by the authors of the paper.

• I believe that autosomal genetic genealogy testing is in its infancy and should only be used with the understanding that the results are only extremely rough estimates that are subject to change as the field develops.

The 2010 paper begins with a brief introduction and a table of most of the companies currently offering genetic ancestry tests.  The paper also discusses many of the issues associated with genetic ancestry tests, including: (i) the differing definitions of ancestry [of which there are many]; (ii) the tools for inferring ancestry; (iii) accuracy of those inferences; and (iv) ancestry and health, among several other things.

Overall, as discussed in great detail below, the authors have done an excellent job of addressing the concerns I raised in my review of their 2008 paper, which I felt was a much poorer review of the field (see below where I’ve compared my concerns from 2008 to the 2010 paper).

The 2010 paper ends with the following two recommendations:

• “Leadership of the human-genetics community, diverse in its interests and its own identities, should develop mechanisms for promoting thoughtful and rigorous use of genetic ancestry estimation in academic research.”

• “Interested scientific and scholarly societies should collaborate to convene a national roundtable discussion of DTC genetic ancestry testing.”

Interestingly, the second recommendation is similar to the one that I made after reviewing the ASHG’s 2008 paper when I stated that “I hope that the Task Force is actively conversing with people outside the committee, including commercial testing entities, researchers, and customers of genetic genealogy in order to obtain a well-rounded view of the field.”

Additionally, the 2010 paper specifically offers an “alternative approach” to federal regulation of genetic ancestry testing (something that I have often and repeatedly stated my disagreement with):

• “Recently, Lee and colleagues called for federal regulation of genetic ancestry testing.  At this juncture, we offer an alternate approach, one that might itself lead to federal oversight, if subsequently deemed appropriate, necessary, or practical.  We believe that effective decision making regarding genetic ancestry inference, in particular DTC genetic ancestry testing, will be best initiated through cooperative interaction among a variety of stakeholders, including suitable federal agencies.  Considering that such collective engagement has not yet occurred, it is premature to assume reticence or resistance on the part of any of the players or that federal regulation is the only recourse.”

I thought it might be an interesting exercise to determine whether the new paper addressed the concerns I raised after reading the 2008 paper.

General Concerns:

• The 2008 Paper – In 2008, I wrote that “[t]here are statements in the paper about psychological reactions to testing results, including the conclusion that ‘[t]he occurrence of or potential for emotional distress in people and groups following receipt of conflicting information about their ancestry has been well documented.’  Unfortunately, the statements are based on anecdotal stories or isolated examples rather than any systematic or scientific investigation of the reactions of individuals to the results of genetic genealogy testing.  I am unaware of any systematic objective study that looks at the reactions of individual to genetic genealogy testing results (outside of the paternity test or health testing arenas).  Indeed, a prior policy paper from the ASHG cites only a BBC documentary that examined the ancestry of three individuals of African descent and a newspaper article to support their conclusion that “[t]est-takers may…suffer emotional distress if test results are unexpected or undesired.”  I would suggest that the Task Force, rather than assume that this “emotional distress” response to genetic genealogy test results has been well documented, conduct an objective study specifically tailored to analyze genetic genealogy testing. The difference between the results of genetic genealogy testing and the results of health or medical testing is so vast that drawing comparisons between the two is extremely problematic and potentially inaccurate.

• • The 2010 Paper – The new paper states that “Knowledge about genetic ancestry, particularly if undesirable and unexpected, can lead to the reshaping of group, familial, or personal identity (cites omitted)…The occurrence of, or potential for, emotional distress in people, families and groups after receipt of conflicting information about their identity through DTC ancestry testing has also been discussed [cites omitted]. Nonetheless, some research focused on consumers of ancestry testing has revealed that although ancestry tests might promote genetic thinking about ancestry and ‘‘race,’’ test takers also were able to construct meaningful narratives of their identity. [citing to Alondra Nelson’s article; see Article Review: “Bio Science: Genetic Genealogy Testing and the Pursuit of African Ancestry”].  Clearly, additional empirical research will need to adequately explore the relationship between genetic ancestry testing and the identities and overall psychological well-being of test takers, their families, and their communities.”

• • Thus, the 2010 statement clearly weakened the stance of negative perceptions from “well-documented” to “has been discussed,” and cites Dr. Nelson’s very interesting research, which suggests that test takers interpret results to meld with their preconceived identity.  The section ends by suggesting that more research is needed, which I suggested in my 2008 review.

• The 2008 Paper – In 2008, I wrote that “[t]he paper muddles the distinction between Y-DNA/mtDNA testing and autosomal testing, even though the differences are huge.  The results of Y-DNA and mtDNA tests are STR numbers, SNP designations, or differences from the CRS which are then used to estimate a haplogroup or compare with another’s results.  Given the extensive data regarding haplogroup designation, the estimates are highly accurate.  Additionally, a haplogroup designation implies only a very broad geographical origin many thousands of years ago; it is not an estimation of genetic ancestry, as the authors of the policy paper imply.  Haplogroup designations have existed for more than 20 years and continue to be used by population geneticists and anthropologists.  The results of autosomal testing, however, are estimations of genetic ancestry.  These autosomal tests look at anywhere from 13 to 500,000 locations – out of billions – on the human genome and return percentages of ancestry based on those markers.  Autosomal testing can be confusing to test-takers because customer often assumes that the percentages are final and represent an accurate picture of their entire genome.”

• • The 2010 Paper – The 2010 statement more clearly breaks up the analysis into the very different fields of “mtDNA and Y Chromosome Markers” and “Autosomal Variants” in one section, and “Lineage Identification with Uniparental Markers” and “Admixture Estimation” in another.

• The 2008 Paper – In 2008, I wrote that “[t]he authors mix the issues associated with the everyday genetic genealogy test-taker with the issues faced by very specific groups of test-takers.  For example, Native American groups are concerned about the effects that genetic genealogy will have on group identity and membership.  These same concerns have also been raised by lineage societies such as the SAR and the Mayflower Society.  Any regulations that a group believes it needs should be at the level of the group, not at the level of the testing! Groups that have these concerns should themselves decide whether and how to use genetic genealogy results for membership and group identity (such as the DAR and Mayflower Society are doing); regulating genetic genealogy at the testing level is not the most efficient or appropriate way for these groups resolve the ethical and social concerns.”

• • The 2010 Paper – The 2010 statement has a section on page 10 that addresses this issue.  It states that “[r]eports of the use (or intended use) of ancestry test results to make claims for benefits through affirmative action or for rights perceived to be associated with their new-found Native American status have increased unease over the loss or gain of certain rights or entitlements,” but reasonably notes that “It remains to be seen what tangible effects (if any) genetic ancestry inference will have on these pre-existing entitlement issues.”  Here, again, the ASHG has addressed my concerns.

• The 2008 Paper – In 2008, I wrote that “[t]here is mixing of the controversial phrase “direct-to-consumer” with genetic genealogy.  Of course it’s direct-to-consumer, who else would the results go to?  Surely the authors of the paper aren’t suggesting that genetic genealogy tests should be ordered and reviewed by a doctor or genetic counselor.  That would be a ridiculous restriction.”

• • The 2010 Paper – The 2010 statement still uses the term DTC, but I think in the last 1.5 years the use of the term in general has been to indicate that the testing is done without the use of a doctor or counselor rather than to suggest that a doctor or counselor should be involved.

• The 2008 Paper – In 2008, I wrote that “[a]lthough I am unaware of the composition of the ASHG Task Force, I hope that it is made up of a diverse group. Additionally, I hope that the Task Force is actively conversing with people outside the committee, including commercial testing entities, researchers, and customers of genetic genealogy in order to obtain a well-rounded view of the field.”

• • The 2010 Paper – The 2010 statement, very much in line with my 2008 recommendation, concludes with the recommendation that there be a “face-to-face conversation among ancestry-testing companies and promoters, consumers, community leaders, advocacy and interest groups, geneticists, social and behavioral scientists, humanists, healthcare providers, legal professionals, federal agencies, media, and other key stakeholders should be to identify major issues of concern and brainstorm practical solutions.”

Thus, with this paper the ASHG appears to have addressed almost every one of the concerns and misconceptions I raised in my review of the 2008 statement and recommendation.  Actually, it’s almost uncanny.  I applaud the committee for their work and thank them for addressing these issues.  Hopefully, when the ASHG’s proposed “national roundtable discussion of DTC genetic ancestry testing” is convened, I will be able to attend.

• Daniel MacArthur at Genetic Future writes “Willful ignorance is not an effective argument against personal genomics,” which is a criticism of an embarrassingly bad op-ed by Camilla Long in the Times (U.K.) entitled “When DNA means do not ask.”  In the article Long mentions several types of genetic testing including “superficial services such as ancestry tests.”  A truly uneducated statement, considering that ancestry tests are among the informative of all genetic tests!

• Like Jasia (congratulations!!), I am truly honored to be on the 15 Genealogy Blogs You Need to Read! list that Leslie Albrecht Huber wrote for the Discovering Family History magazine.  I wasn’t previously aware of this magazine, so this was a great way to get their name out.  Thank you again!!  (via the  Family Matters blog).

• Thank you to Access DNA for including The Genetic Genealogist in their list of “Top 5 Genetics/Genomics Blogs“!!  Are you reading the Access DNA blog?

• Brad Templeton at Brad Ideas writes “The odds of knowing your cousins: 23andme Part 1” and “The privacy risks of genetic genealogy (23andMe part 2),” and”Haplogroups, Haplotypes and genealogy, oh my.”  I certainly don’t agree with everything he writes (including how dismissive he is of traditional genetic genealogy, which has fueled DTC genomics for the past 1o years), but the articles are worth a quick read.

• There’s a terrific discussion in the comments to “Genetic ancestry testing: people who don’t want to know” about people who refuse to undergo genetic ancestry testing for personal reasons.  I added my own 2 cents at comment 17 trying to explain some of the most common misunderstandings surrounding autosomal DNA testing.

Randy Seaver at Genea-Musings (“I’m Puzzled by DNA Claims on ‘Faces of America’”) writes about the fourth and last episode of “Faces of America,” a PBS documentary series investigating the ancestry of several famous people in America. This fourth episode included several different types of genetic genealogy to examine the ancestral origins and relatedness of the show’s members.

1. Whole Genome Sequencing by Knome

The first type of genetic genealogy was whole-genome sequencing by Knome of Henry Louis Gates and his father. This analysis examined Henry’s (“Skip’s”) genome for medical conditions and physical traits, and also compared his DNA to his father’s, thereby allowing them to deduce the entire DNA contribution from his deceased mother. This segment was actually quite moving, as Dr. Gates was able to establish this intimate connection to the mother that he and his father obviously missed very much.

2. SNP Analysis by 23andMe

The second type of analysis was large-scale SNP analysis of everyone’s genome by 23andMe. The show primarily focused on the Ancestry Painting, which uses information from throughout the entire genome to determine a very rough estimate of your ancestry. Ancestry Painting breaks down the genome into three categories: Asian/Native American, European, and African. Stephen Colbert, for example, was 100% European, while Eva Longoria was 70% European, 27% Asian/indigenous, and 3% African. I don’t recall any mention or use of 23andMe’s medical or physical trait analysis in the show.

3. mtDNA and Y-DNA Haplogroups

The third type of genetic genealogy was haplogroup testing. In this segment, Dr. Gates spoke with Dr. Bryan Sykes of Oxford Ancestors, which was interesting because it was the first time I’ve ever seen him speak. There didn’t appear to be any surprises here.

4. Mysterious Genomic Comparisons

The fourth type of genetic genealogy testing in the episode is what has caused so much confusion among genealogists. Dr. Gates introduced David Altschuler and Mark Daily as “research geneticists at the Broad Institute.” According to Dr. Gates, Altschuler and Daily have “pioneered a new kind of genetic analysis that can determine if any two people share a common ancestor within the last several centuries.” Although Dr. Gates repeatedly said within the last “250 years”, the scientists repeatedly said “hundreds of years.” A slight difference perhaps, but I tended to disregard the “250 years” as more of a simplification by Gates for purposes of the show rather than any actual limit discussed by the scientists. Regardless, this doesn’t make their analysis any more clear.

Unfortunately, I have been unable to locate any discussion, literature, or publication by Altschuler or Daily (or anyone else) discussing this “new kind” of genetic analysis. If you’re familiar with one, please point it out in the comments so that we can understand their analysis.

Interestingly, the members of the series apparently did not match each other in 23andMe’s Family Finder, since the 23andMe system would have picked up on that, and further analysis would not have been necessary. And since it appeared that they did NOT undergo further testing, I imagine they used their 23andMe data for the analysis by Altschuler and Daily.

As an example of this comparison, according to Altschuler and Daily, Yo-Yo Ma (who was 100% Asian in his 23andMe Ancestry Painting) is related to Eva Longoria (who was 70% European, 27% Asian/indigenous, and 3% African) within the last few centuries. It obviously wasn’t through Native American DNA since any connection there was many, many thousands of years ago. Does Longoria have more recent Asian DNA perhaps? It seems unlikely (but is certainly not impossible). The fact that this was simply glossed over was an oversight.

I’m having a hard time understanding the results from Altschuler and Daily.  Can anyone else shed any light on their analysis?

Conclusion

Despite the confusion created by the fourth type of genetic analysis, I really enjoyed this episode of Faces of America. As always, it was interesting and entertaining to watch them receive their results and explore their ancestry.

What are your thoughts?

Familybuilder, launched in 2007, is a genealogy company that ranks among the top 10 online genealogy services in the world with over 17 million users and over 120 million family tree profiles.  Late last year the company began offering a genetic genealogy product, as I wrote about here on the blog (see “Familybuilder Announces DNA Testing”).

Disclosure: This is a review of Familybuilder’s Y-DNA service using a kit I received free of charge for purposes of this review.  Please note that this is not meant to be an endorsement but merely a review of the Y-DNA service offered by Familybuilder.

The results of a Familybuilder Y-DNA test includes:

“The Migration Map for you and your ancestors, your 17 Markers, your Haplogroup and the History of your DNA.  In addition, the ability to share your results with family and friends on social networks such as Facebook and MySpace as well as a downloadable PDF (suitable for framing).”

I received the following kit in the mail for the Y-DNA testing, which included a swab, detailed instructions, and a return envelope:

Since I have already tested my Y-DNA, I asked a male relative to take this Y-DNA test.  This surname, Conger, is believed to have originated with a John Belconger who emigrated in 1665 from Great Yarmouth, Norfolk, England to Newbury, Massachusetts and later Woodbridge, New Jersey.  Although there are likely many descendants of John Belconger in the United States, as far as I know there is only one other Conger who has undergone genetic genealogy testing, as discussed below.

After roughly four weeks, I received an email from Familybuilder that my DNA test results were ready (although my name is listed, these are a relative’s results, not mine).  Not surprisingly since the surname appears to have originated in Western Europe, the Y-DNA belongs to Haplogroup R:

With the results, Familybuilder included information about the predicted haplogroup.  The description for Haplogroup R, for example, includes the following snippets:

“ORIGIN – Haplogroup R descended from Haplogroup P (M45) in Central Asia.  About 30,000 years ago, one of the tribes in Central Asia moved towards the European subcontinent.  It is in this group that the first M207 mutation (Haplogroup R) occurred.”

“MIGRATION AND SPREAD – The highest frequency of Haplogroup R is found in Western Europe, where populations carrying R1b typically reach 75% frequency.”

Familybuilder also compares an individual’s results to results in their database in order to discover potential matches.  Unfortunately, as shown below, there were no matches with the Conger Y-DNA profile from the Familybuilder database:

Since there were no results in the database, I entered the results into Ysearch to potentially identify matches (see Ysearch User ID 4KTQB).  A search for matches with a genetic distance of 0 among people who tested at least 13 of the same markers turned up 19 matches, although none with the same “Conger” surname.  Outside of the United States, the most distant male ancestors for these matches are mostly from the U.K.

Interestingly, there is another Conger in the Ysearch database (User ID 4MSTZ), but his Y-DNA belongs to Haplogroup J2.  With these two tests, therefore, we have shown for the first time that not all Congers in the U.S. are descended from the same man.

Familybuilder also offers a “Print My DNA” and “Share My DNA” features, which allow users to share their results with friends and family.  The Share My DNA feature formats the results, for example, for easy posting to websites or social media such as Facebook.  See the following link for a nice display of the Conger results.

Lastly, Familybuilder also offers a new “Groups” feature as of October of 2009.  From the recent press release:

“Familybuilder DNA has added a new feature within their ancestral DNA Test Kits called DNA Groups. This feature allows consumers to create and manage their own groups based on commonalities such as a shared haplogroup, surname, national origin or current location. With DNA tests being a major tool for people searching for more information on their family histories, this feature takes the collaborative nature of genealogists to a digital forum. “By creating groups, users can collaborate with one another to piece together their family stories,” said Ilya Nikolayev, CEO of Familybuilder. Recently adding a DNA Matching Tool, this new feature allows consumers to engage with one another in new ways beyond traditional genealogical mechanisms.”

A Familybuilder Y-DNA test normally costs $59.95.  Familybuilder uses a state-of-the-art laboratory facility with ISO/IEC and ASCLD Lab Accreditation for testing.

You can follow Familybuilder on Twitter and Facebook.

I recently received an interesting question from a reader (see this comment) about 23andMe’s Relative Finder, and thought it would be worth sharing the question and my answer with all my readers.

The Question:

I’m a man who recently took a 23andMe test, and I have a question about Relative Finder.  Another man who I match on 36 of 37 Y-DNA markers via Family Tree DNA also took a 23andMe test.  We believe that we are third cousins, but this individual does not show up as related in Relative Finder, nor does he show any similarities in the Family Inheritance section.  Does this mean that we are not related at all?

The Answer

If two individuals do not share any DNA in the Family Inheritance section of 23andMe or do not appear as relatives in Relative Finder, this absolutely does not mean that they are not or cannot be relatives.  It does suggest, however, that the two individuals might not share any DNA.  Although your Y-DNA test suggests that you share a recent common male ancestor, it appears that apart from your Y chromosomes you do not share any other DNA.

DNA is randomly passed down from generation to generation.  A parent does not pass on their entire genetic makeup to a child; as a result, bits and pieces of DNA are lost in each generation.

Cousins will only share DNA if they happen to have randomly inherited that DNA from their shared ancestors.  With each generation that separates the cousins, the probability that they share DNA decreases, because with every generation it is more likely that they will not inherit DNA from their ever-more-remote shared ancestors.

Third cousins, for example, share only 2 of their 16 ancestors at 4 generations.  In this example, it appears that those two ancestors did not contribute an identical segment to both you and your third cousin.  Interestingly, it is possible that both you and your cousin have segments of DNA from these ancestors, but they wouldn’t show up as a match in Family Inheritance or Relative Finder unless they were the same segment of DNA.

Also keep in mind that a 23andMe test is only comparing those sections of the DNA that are examined by the test; a whole-genome test, currently not available to consumers (at least at an affordable price), is the only test that can compare an individual’s entire DNA makeup to another’s.

Two Family Trees

In reality, everyone has two family trees.  The first is a Genealogical Tree, which is every ancestor in history that had a child who had a child who had a child that ultimately led to you.  Every decision made by every person in that tree contributed to who and what you are today.

However, not every person in that tree contributed a segment of your DNA sequence (because of random inheritance, as discussed above).  As a result, we have a second family tree - a Genetic Tree – which is a tree that contains only those ancestors who contributed to our DNA.  No one has yet been able to construct their Genetic Tree, but soon it will be a reality thanks to advances in genetic sequencing and comparison such Relative Finder.  These tools are using relatedness between people living today to deduce the inheritance of DNA from people who have been dead for centuries.

I have many questions about Genetic Trees that I’m looking forward to answering with new tools in the future, including the following:

• At 10 generations, I have approximately 1024 ancestors (although I know there is some overlap).  How many of these ancestors are part of my Genetic Tree?  Is it a very small number?  A surprisingly large number?
• What percentage, on average, of an individual’s genealogical tree at X generations is part of their genetic tree?

What questions about Genetic Trees can you come up with?

• DNA Test Index has a great index of DNA testing providers, including genetic genealogy testing companies.  Via @genomicslawyer – an atypically complete list of genetic test providers: http://bit.ly/2f8FLW.

• ISOGG, the International Society of Genetic Genealogy, has a new information page at “I’ve Tested at 23andMe, Now What?“  The site includes a variety of tools to help you further explore your ancestry, including EURO-DNA-CALC and Promethease, among others.

• Family Tree DNA has a new Holiday Sale, as summarized at the U4 Haplogroup website.  The FTDNA ordering page also has the holiday prices.

• Linda Avey, co-founder of 23andMe, has started a new blog entitled The Life & Times of Lilly Mendel.  I’m looking forward to some interesting reading as Linda establishes the Brainstorm Research Foundation dedicated to the study of Alzheimer’s disease.

• The Genomics Law Report continues the fascinating What ELSI is New? series, including a contribution from yours truly.

On July 8th, Ancestry.com hosted a webinar called “Genetic Genealogy Made Easy.”  The webinar is now posted and can be accessed at any time.  One great thing about a webinar is that it can be multimedia; indeed, this webinar uses both slides and video.

The presentation is pretty basic, but a good source of information for people who are new to genetic genealogy.  The following topics are covered, according to the site:

- DNA testing for genealogy works–in easy terms.
- To understand and apply your results to grow your tree.
- Ancestry.com DNA testing can continue to pay off for years.
- Women can benefit from a paternal lineage test.
- To use Ancestry.com DNA features: Groups, Transfer to Tree, and Ancient Ancestry.

Ancestry.com is planning more advanced genetic genealogy webinars in the future.

What is interesting is that the last question from the audience addressed by the webinar regards using genetic genealogy by adoptees.  Whenever I give presentations, I almost invariably receive this question in one form or another.  Seems to be a very common question.

Last month I wrote “Unlocking the Genealogical Secrets of the X Chromosome” and posted a few charts that show the inheritance of the X-chromosome through 8 generations.  I thought these charts might be helpful since inheritance of the X-chromosome can be difficult to understand without seeing it.

New Chart with Ahnentafel Numbers

Since posting the article, two new charts have been created using the originals.  I made one, and the other was made by Rodney Jewett (who gave me permission to re-post the chart here) and posted at dna-forums.org.

Mr. Jewett added the Ahnentafel numbers of contributing X-chromosome ancestors to the chart.  Using these numbers, an individual can simply create a numbered Ahnentafel report to identify X-chromosome contributing ancestors using this chart:

Note that Ann Turner also has a text file of the Ahnentafel numbers of those ancestors who potentially contributed to the X chromosome, through 10 generations.

New Chart Showing Contribution Percentages

I’ve been very intrigued by all the recent discussion of the X-chromosome in the genetic genealogy context, and I’ve been exposed to some facts about the X-chromosome of which I previously was unaware.

For instance, I kept seeing statements that suggested that different ancestors in each generation contributed different amounts to the X chromosome.  I read that at the 8th generation, one ancestor contributes 1/8th, some contribute 1/64th, and the others contribute between 1/16th and 1/32nd.  I kept trying to understand this, but I had to chart it out to grasp it.  Although this chart is for a male, I believe it will also work for a female by adjusting the generations slightly.  The chart is big so it might take a moment to download:

Thus, the chart shows that if you are a male, your mother’s father’s mother’s father’s mother’s father’s mother contributed 1/8th of your X-chromosome, while your mother’s mother’s mother’s mother’s mother’s mother’s parents only contributed 1/64th.

Now, keep in mind that this chart serves only as a very rough guideline for inheritance.  Although males pass the X chromosome largely unchanged to their daughters, females will usually pass a mixed X chromosome to their child a mixture of the X chromosome they received from their father and the X chromosome they received from their mother. However, a child is unlikely to receive an X chromosome from their mother that is 50% from their maternal grandfather and 50% from their maternal grandmother – it will most likely be some other more random amount between 0% and 100%.  Thus, an ancestor is likely to be either under- or over-represented in an actual X chromosome.

Please, if you find any errors in my chart, please feel free to email me and I’ll do my best to correct them.

Potential Research

With the advent of affordable sequencing, I would love to see a study that examined X-chromosome inheritance in a family of 6 or 8 generations.  How closely would it match the theoretical inheritance probabilities from the chart above?  It’s probably just a matter of time before this research is conducted.

P.S. – Feel free to use these charts, but please give proper credit.

A new article in Ancestry Magazine, “Meeting My New Family,” details a recent meeting of genetic relatives in Chicago.  The author is Howard Wolinsky, who has written other articles in the field of genetic genealogy (see, for example, an article in EMBO about 2 years ago).  As Howard describes, the meeting wasn’t a traditional family reunion:

“We are a new kind of cousin. Until a few days ago, we were strangers who just happened to have had our DNA analyzed. Then we discovered we matched one another to varying degrees. Most of us have common Jewish connections. And we learned that we come from relatively rare branches of the human DNA tree. Our mothers’ mothers came from the HV branch. Our fathers’ fathers came from the G group.”

The full text of the article is here.