Saturday, March 10, 2018

Spit or Swab?

Most of us who have done DNA testing have anecdotal impressions about the success of "spit tests" and "swab tests" for collecting DNA samples. Some of us may still have skepticism about whether a little saliva can provide accurate scientific results. On this later question, I was reassured shortly after we moved to Nashville in 2012. In late 2009 my wife and I had been beta testers for 23andMe when the company was expanding from health related testing to ancestry testing. As a result we both had pre-FDA intervention reports on multiple potential health conditions and drug interactions.

Although I wanted to believe the results, I was born in Missouri -- the Show Me state. Therefore, I had a bit of residual skepticism. Shortly after we arrived in Nashville, we enrolled in Vanderbilt University Medical Center's PREDICT program which aimed at matching drug reaction information with patients' electronic medical records. For this program blood was drawn in a clinical setting and was processed in the Medical Center's labs. On a half dozen comparable tests, both my wife and I got results and interpretations from Vanderbilt that validated those we have previously received based on 23andMe's spit tests. My wife was flagged for statins and I was identified as a faster than average metabolizer of certain blood thinners by both our spit tests and our blood tests. Saliva DNA tests seemed to work just fine.  

However, the question of whether spit tests or swab tests were more likely to get usable results in the lab still remained. My wife sometimes says that her family has a "no spit" gene. It took her three tries to produce a usable sample for Ancestry. It took her sister two tries at Ancestry. Their brother was never successful in producing a readable sample for 23andMe. After two tries the company refunded his money. 

I just retested a grandson a spit test for 23andMe and that result is still pending. The grandson is not biologically related to my wife's family. 

All four of the above family members have passed swab tests on the first try with MyHeritage or FTDNA. Most of you know that samples sent to these two companies are processed through the same lab in Houston.

The Poll:

How unusual is my wife's family? Maybe I should rephrase that. How unusual is their DNA testing success? To cast a wider net to collect some data I posted a poll this week on the "Genetic Genealogy Tips and Techniques" Facebook page which claims more than 36,000 members. For a variety of reasons this turned out to be a "quick and dirty" data collection survey. I was not clever enough to bend Facebook's poll instrument to allow responders to easily enter multiple results when multiple family members had been tested. All the data is self reported from customers. I tried to enter data customers provided in comments. My quick and unscientific poll ended up with 1.333 usable testing experiences.


While testing companies will claim a higher success rate than is shown in my results, I would welcome their data to prove it. Intuitively, these data seem to reflect what many of us experience. This is not intended to be the definitive final word on this question. What do you think?

I'd love to have more data. 


Saturday, February 17, 2018

Inheriting atDNA from 3rd Great-grandparents

Recently I have transferred to or tested about three dozen extended family members at MyHeritage. The recent upgrading of the tools by MyHeritage has moved the company's DNA services into the 21st century. If you haven't taken a look in the last month, you owe it to yourself to do so.

About a week ago I discovered a match from Germany for the maternal grandmother of my three Dowell grandsons. 

Those of you who are perceptive genetic genealogists will recognize that this amount of shared atDNA is well within the bullseye of what 2nd cousins would be expected to share. It also could be on the fringe of what could be expected if the two were one generation removed from each other within their families.

Particularly since my in law had been born in Germany, this appeared to be a match well worth pursuing. My interest was intensified when I discovered that "Weirauch" was one of the family surnames listed by the match.

Looking farther down the match list, I found my daughter-in-law:
She matched her mother as a daughter and shared a little less than half the atDNA her mother did. This would be about what we would expect because she was a generation farther removed from the matched individual.

Continuing down the match list I discovered my three Dowell grandsons. They were listed based on the amount of atDNA they shared with their maternal grandmother since it was her account I was using for this investigation. Those of you who read my blog posts a few months ago about how each of my grandsons inherited their atDNA from each of their four grandparents will not be surprised that MyHeritage reported their match with her ranged from almost 35% down to just over 23%. 

The boys are second cousins -- twice removed since the match is a second cousin of their grandmother. As such they would be expected to share about as much atDNA as third cousins and they do. However, I was surprised to find that the grandson who shared the most atDNA with his maternal grandmother, shared the least of the three with her second cousin. This is one more example to remind us of the random nature of atDNA inheritance. I guess I should learn not to assume predictability and just observe the data. 

Yes, this did turn out to be grandma's second cousin with whom communications had been lost when part of the family immigrated to America. A reunion is in the works that will include the grandparents, the parents and the grandsons during their spring school holiday in a few weeks. 

The source of the matching at DNA:

The connection of my grandsons with their newly discovered second cousin --twice removed is through a common descent from Max Weiranch (1878-1923) and Paulene Mittman (1878-1934) who were both born and died in Brieg, Schlesien. Max and Paulene were the boy's 3rd great-grandparents and between them they made a contribution that lives on in each of the boy's atDNA.


Each grandson inherited an identifiable and similar but different pattern of atDNA from this set of 3rd great-grandparents.