Test ALL family members even full siblings

Earlier this year I reported on what I was learning from the autosomal DNA tests of my three grandsons who are now 10, 7 and 3. I am continuing to learn more as I examine their results in different ways. They were all tested through MyHeritage and then their results were imported into FTDNA's Family Finder to be able to compare them more easily with other family members.

The earlier posts can be viewed: 

• How autosomal DNA is inherited: 3 siblings compared; 
• Unintended Consequence;
• Ethnic Origins Predictions Affected by Random Autosomal Inheritance; 
• Grandsons' DNA continued; and
• Why don't I have as many DNA matches as ....?

In this post I will comment on what I learned when I mapped segments of my grandsons' DNA using Kitty Cooper's tool and Family Finder's Chromosome browser. 

For those of you who do not personally know these fine young men, the takeaway from all of this is to realize how each inherited very different segments of DNA from each of their 4 grandparents and the one great-grandparent from whom we have a DNA sample. The implications of this for genetic genealogists are that when we are administering autosomal tests we should test as many family members as possible. Even full siblings will have quite different match results. 

Numbers of matches reported will depend greatly on the extent to which autosomal DNA testing has penetrated the geographic and ethnic groups from which the test takers descend. In the case above, one grandfather is Ashkenazi and his spouse comes from another area of Eastern Europe but is not genetically Ashkenazi. The differences in their numbers of matches is astounding. These match numbers carry down two generations to their grandchildren. It depends on how much of their autosomal DNA each of the grandchildren inherited from each individual grandparent.

Oct 1st, 2017	Matches on Family Finder	Ashkenazi
Simon	5,999	26%
Noah	4,944	22%
Benjamin	3,732	15%
Monika Deutscher Katzel	502	0%
Lester Katzel	12,787	97%
Dave	3,306	0%
Arlene	2,427	0%
Shana (Katzel) Dowell	6,930	42%
Frederick Deutscher	466	0%

When you are formulating a DNA testing plan, administer an autosomal DNA test to as many family members of each generation as you can possibly afford to test. Each person tested will contribute something to the family mosaic. The results in all families will not be as dramatic as in this family but the results that each additional person contributes can be just as significant.

As a postscript, the contribution shown above for grandmother Monika could also be attributed to her mother as her father's contribution is accounted for separately. 

How autosomal DNA is inherited: 3 siblings compared

If you know how much aDNA you inherited from a grandparent or great-grandparent, can you calculate how much you inherited from that person's spouse?

By now most of us know that each of us get half of our autosomal DNA from our mom and half from our dad. But how we inherit from earlier generations of our ancestors is less well understood. We are generally told after that first generation the inheritance pattern is random. However, we often see charts that show we should expect to inherit about 25% from each grandparent and 12.5% from each great-grandparent, etc. Are there any additional rules?

Below is a small case study that explores these issues:

Inheritance from maternal grandparents are shown in the left hemispheres above and paternal contributions are in the right hemispheres.

The chart above shows how much aDNA each of three brothers inherited from each of their grandparents. Only the middle one, Grandson 2, came close to the 25% average we might expect. However, note that each grandson inherited exactly 50% from his maternal grandparents and 50% from his paternal grandparents. However, the amount inherited from each individual within a set of grandparents varied considerably. The exact percentages can be seen in the table below.

As noted above Grandson 2 came the closest to the theoretical 25% inheritance rate. The aDNA inherited by Grandson 1 was skewed somewhat from that distribution. The practical implications for even this amount of variation can be important to your genealogical research. 

In this example the maternal grandfather is Ashkenazi -- a group that statistically has been over sampled in genetic genealogy databases. He had more than eleven thousand matches in FTDNA's Family Finder. The maternal grandmother came from an area in Eastern Europe very near the origin of her mate; but she was non-Ashkenazi. She had less than five hundred matches in Family Finder. The 4% difference in the amount of Ashkenazi DNA inherited resulted in Grandson 2 having more than five thousand matches while his full brother, Grandson 1, had about a thousand matches less. This also had a noticeable difference in their ethnicity predictions. 

When Grandson 3's Family Finder results are reported, it is expected that his matches and ethnicity predictions will vary ever further from those of his two brothers -- particularly Grandson 2. As we will see below, Grandson 3 inherited more aDNA from his great-grandfather -- the father of his maternal grandmother -- than the 15% he inherited from his Ashkenazi grandfather.

All the results above are based on actual test results. However, if one of the grandparents had not been tested, we could have calculated their contribution. Even if two had not tested we could have calculated their contributions IF we had results from each of their spouses. You have probably already figured out that the contribution of the missing grandparent spouse would be 50% minus the contribution of their known spouse.

[The portion below is being revised to take into account the error in my thinking pointed out by Philip Gammon in his comment below. That revision will be posted tomorrow, October 6th.]

This kind of calculation becomes more relevant in the current case when I took a look at contributions from great-grandparents. We only have actual test results from one great-grandparent who was tested a decade ago about a year before he died in his mid 90s. So we can use his actual test results and also use them to calculate the aDNA contribution of his wife. By now you probably know that the hypothesized contribution will be constructed by subtracting his tested aDNA amount from 25% -- the total contribution of each pair of biological great-grandparents.

For the oldest brother it turns out that the tested great-grandfather had contributed 12.4% of his autosomal DNA. This is very close to the theoretical 12.5%. This left 12.6% for the great-grandmother to have contributed.

 

However, the second and third brothers received a more uneven contribution from this pair of great-grandparents. One received a greater than expected amount from the great-grandmother and the other from the great-grandfather. The tested great-grandfather had passed down 10.3% of the aDNA of the second brother and 16.6% of the aDNA of the third brother. In fact the 16.6% of his overall aDNA that the third brother received through his maternal grandmother and mother was more total aDNA than this brother had inherited from his paternal grandfather (15%, see above). This result was surprising but perhaps not unusual. We are preconditioned to expect that we received about one half the amount of aDNA from each ancestor in each receding ancestral generation. In this case that expectation was confounded because of the large amount of maternally inherited aDNA that the mother of the brothers had passed down to her third son. Although the mother had inherited half of her own aDNA from each of her parents, what she passed down to the third son had disproportionately represented what she had inherited from her mother by a ration of more that two to one -- 35% to 15%.

The second son inherited more of the calculated contribution from his great-grandmother than either of his brothers. He inherited 14.7% versus their 12.6% and 8.4%.

The third son inherited the most aDNA from the tested great-grandfather and did so by a considerable ratio. Although his 16.6% inheritance does not seem like a big difference from the 12.4% of one brother and the 10.3% of the other, it is about 35% more than one and 63% more than the other. In terms of inherited ethnicity and traits, these could matter.

The Takeaways:
   
1. We inherit 50% of our aDNA from each parent; 50% from each set of grandparents; 25% from each set of great-grandparents, etc.
2. We often inherit significantly different amounts of aDNA from each member of a set of ancestors.
3. Even full siblings often inherit significantly different amounts of aDNA from each of their grandparents and great-grandparents.
4. These differences can significantly affect the numbers of autosomal matches reported for each sibling.
5. These differences can significantly affect ethnicity estimates.
6. These differences can significantly affect health and other heritable characteristics.
7. The contributions of some ancestors can begin to fade significantly within two or three generations while those of others can remain robust much longer.
8. If you have test results for at least one grandparent or great-grandparent, you can calculate the aDNA contribution of their partners.

Why don't I have as many DNA matches as ....?

It seems that almost daily someone writes on one of the Facebook genealogy sites, "Why don't I match the person that my relative does?" We have the stock answers that include autosomal DNA is inherited in a random manner. Rarely have I seen this so vividly illustrated as in the results of two of my grandsons. In earlier posts the last several days, I have pointed out that each of them inherited different amounts as well as different segments from each of their four grandparents. If this much variation can occur in just two generations, it can really be skewed as it is compounded over four or five generation.

The first of my three previous posts on this subject demonstrated that grandchildren do not inherit equal amounts of atDNA from each grandparent although it appears that each set of grandparents contribute 50%. To review this post click here.

In a follow-up post I demonstrated that these variances of amounts of atDNA inherited by grandchild can alter ethnic predictions between full siblings. To review this post click here.

In yesterday's post I used Family Finder's chromosome browser tool to illustrate how each segment larger than 5 cM of DNA was inherited by each of my grandsons from each set of their grandparents. To review this post click here.

After my post yesterday, Ann Turner asked if I would be willing to do more analysis on the matching segments the two of my grandsons inherited from their four grandparents by dropping the threshold from 5 cM down to 1 cM. In preparing the data to send to Ann for her analysis, I noticed that the two grandsons had vastly different numbers of matches on Family Finder. One had 23% more than his brother. These numbers were not trivial. One had almost a thousand more than the other. How could this be if they were really full siblings?

It largely depends on who is in the database. Groups from different parts of the world are unevenly represented in various DNA databases. The FTDNA database has a disproportionally heavy presence of Ashkenazi Jews. The maternal grandfather shown below has a high percentage of Ashkenazi ancestry. FTDNA has been able to identify about 90% of his atDNA as being of Ashkenazi origin. His number of matches in the database far exceed the number of matches reported from any of the other three grandparents. Conclusion: the grandson who inherited the most DNA from his paternal grandfather will have the most matches in this database.

Grandson #1 below only inherited 22.1% of his atDNA from his maternal (Ashkenazi) grandfather. Statistically normal would be 25%. He did dip into the treasure trove of Ashkenazi results in the database. 18% of his DNA is shown to be of Ashkenazi origins. However, he did not inherit DNA of that origin to the extent his brother did. This grandson inherited 28% of his DNA from his maternal grandmother whose ancestors came from areas of Central Europe that are underrepresented in this database. She currently has less than 400 matches. So the combination of the DNA he inherited from his grandmother (along with her scant matches) and did not inherit from his grandfather was largely responsible for him having over 900 fewer matches than his brother. 

Matching  Relatives	Total	Paternal	Maternal	Both
Grandson #1	3,930	935	1,338	1
Grandson #2	4,831	797	1,957	1
Paternal Grandfather	2,682	247	478	6
Paternal Grandmother	1,956
Maternal Grandfather	10,185
Maternal Grandmother	390	83
Mother	5,578	3,530	47	2
Father	2,397	785	739	7

Grandson #2 inherited 26.2% of his atDNA from his Ashkenazi grandfather. That may not sound like a big difference. However it is approximately a 19% increase from the amount inherited by grandson #1.

Even though the maternal grandfather seems to have won the lottery with more than ten thousand DNA matches, his pedigree chart is so short that we cannot yet begin to sort any of those matches into paternal and maternal ancestors.

The paternal grandmother has an extensive pedigree chart; but as yet she has not added it to her Family Finder account.

The mother (my daughter-in-law) seems to have the number of matches that is near the average of her Ashkenazi father and her match deprived mother.

The father (my son) also seems to have the number of matches that is about the average of his parents.

Why do you have the number of autosomal matches that you do?

Grandsons' DNA continued

Earlier this week I made a free transfer of two of my grandsons' atDNA results from MyHeritage to Family Tree DNA (FTDNA). Since the lab testing for MyHeritage is done in FTDNA's Houston lab, this is a fairly seamless process. As with any new procedure there were a couple of minor obstacles. FTDNA had yet to upgrade the Autosomal Transfers entry icon to mention that MyHeritage kits could also be transferred.

Also, there were no instructions that the "-" needed to be removed from the MyHeritage kit number before FTDNA could be identified and validated. Example: MH-XXXXXX needed to become MHXXXXXX before the transfer could be initiated. These transfers were completed within a few hours and allowed me to use Family Finder's chromosome browser tool.

I was then able to continue my learning process which had begun a couple of weeks ago when I received access to these results at MyHeritage. My previous posts demonstrated that grandchildren do not inherit equal amounts of atDNA from each grandparent although it appears that each set of grandparents contribute 50%. To review this post click here.

I then made a follow-up post in which I demonstrated that these variances of amounts of atDNA inherited by a grandchild can alter ethnic predictions between full siblings. To review this post click here. If these changes sometimes can be observed within only two generations, we can only imagine how they could be skewed over five or six generations of compounded random inheritance. This explains a big part of the differences between ethnicity predictions of full siblings.


On to the Chromosome Browser
Using Family Finder's Chromosome Browser tool, I examined the contributions each set of grandparents made to each of the two grandsons. This process allowed me to visualize things I sort of knew intellectually:

• Each set of grandparents combined to pass down 50% of the grandchild's atDNA but the grandparents within each set did not contribute equal amounts;
• Each grandparent's contribution to full siblings differs -- sometimes in measurable amounts;
• There really are two different strands of atDNA inherited by children -- one from the father and one from the mother;
• We can visualize the "crossovers" on the paternal and on the maternal strand of atDNA inherited by the grandchildren and thereby trace which part of the grandchild's atDNA was inherited from each grandparent; and
• Grandsons do not inherit any xDNA from their paternal grandparents.

Maternal grandparent contribution

In this image the atDNA contribution of maternal grandparents are charted for grandson #1. Note that xDNA was inherited from the maternal grandparents through the child's mother. In this case about 28% of the grandson's atDNA was inherited from the maternal grandmother (represented by the orange bars). About 22% came from the maternal grandfather (represented by the bright blue bars). Crossover points are clearly visible where the contributed atDNA shifts from the maternal grandmother to the maternal grandfather on this maternal contributed strand.

In this image the atDNA contribution of maternal grandparents are charted for grandson #2. Note that xDNA was inherited from the maternal grandparents through the child's mother. In this case about 26% of the grandson's atDNA was inherited from the maternal grandfather (represented by the orange bars). About 24% came from the maternal grandmother (represented by the bright blue bars).

Paternal grandparent contribution

In this image the atDNA contribution of the paternal grandparents are charted for grandson #1. Note than no xDNA was inherited from the paternal grandparents through the child's father. In this case about 28% of the grandson's atDNA was paternal grandfather (represented by the orange bars). About 22% was inherited from the paternal grandmother (represented by the bright blue bars).    

In this image the atDNA contribution of the paternal grandparents are charted for grandson #2. Note than no xDNA was inherited from the paternal grandparents through the child's father. In this case about 26% of the grandson's atDNA was paternal grandfather (represented by the orange bars). About 24% was inherited from the paternal grandmother (represented by the bright blue bars). 

Ashkenazi Origins

One other item of interest to report came out of this exercise. Family Finder identified more Ashkenazi DNA from both grandsons than did MyHeritage. One grandson appears to have inherited about 22% of his atDNA from his primarily Ashkenazi grandfather. No other grandparents have been shown to have any Ashkenazi inheritance. Family Finder Identified about 18% of this grandson's atDNA to be Ashkenazi.

The other grandson appears to have inherited about 26% of his atDNA from that Grandfather. Family Finder identified about 21% of this grandson's atDNA to be of Ashkenazi origin.

MyHeritage had identified  the first grandson to have 10.8% Ashkenazi and the second one to have 17.5%.

Ethnic Origins Predictions Affected by Random Autosomal Inheritance

Predictions of our ethnic origins are one of the biggest draws to get people to order a DNA testing kit. Almost all of these predictions are based on our autosomal DNA. That's the only DNA tested by Ancestry, 23andMe and MyHeritage. Family Tree DNA offers these predictions as part of its Family Finder test results. Marketing surveys suggest that more more than half of millennials who take genealogy DNA tests are doing it only or primarily to find out whether they should be wearing kilts or lederhosen to the next family gathering. 

In spite of the warnings of prominent genetic genealogists that these projections at present are one of the softest parts of the science of genetic genealogy, the advertising seen on television and elsewhere continues to emphasize predictions of ethnic origins. 

The Legal Genealogist, Judy G. Russell, is one of the most outspoken critics of the credibility of the predictions we are given. In an August 14, 2016 blog post "Those Percentages, if you must", she reiterated:

The Legal Genealogist says that the ethnicity estimates part of autosomal DNA tests are not a whole lot more than cocktail party conversation,

It just doesn’t seem to matter.

Really.

You can’t rely on DNA tests to give you exact percentages of your ethnic origins beyond the continental level (European, versus African, versus Asian).

 
Judy's conclusion is a valid one. Part of the problem is that this part of our science is still immature: 

1. The population geneticists really can't tell us where all of our ancestors were living 500 years ago;
2. Very few of us have pedigree charts that inform us about who all of our genealogical ancestors were in 1500 and where they resided; 
3. Although atDNA tests generally sample 500,000 to 700,000 locations to make these ethnic predictions, this is a small percentage of our entire genomes; AND   
4. Inheritance of our atDNA is random.

We all know that we inherited 50% of our atDNA from our fathers and 50% from our mothers. But how many of us know how much of our atDNA we inherited from our maternal grandfather? Would this make a difference in our predicted ethnicity? Of course it would.

Last month I published results from atDNA tests taken by two of my grandsons at MyHeritage. They are full siblings. Their other grandfather is primarily Ashkenazi. His Family Finder origins prediction is shown below. 

None of the other three grandparents show the presence of any Ashkenazi genetic component in their Family Finder results. My daughter-in-law was reported in her Family Finder results to be 42% Ashkenazi. [23andMe reported 48%.] Although I am not comparing apples to oranges in this post, I may be comparing different varieties of apples to each other by comparing testing results from three different companies. However, different family members have tested at different companies. These cross testing companies comparisons should not effect my main point in this post. If you have data that would dispute that, please share and we all will learn something.

My main point is that my grandson who appeared to inherit only 22% of his atDNA from his Ashkenazi grandfather in my previous post, was shown by Family Finder to have significantly less Ashkenazi ethnicity than did his full sibling who appears to have inherited 26% of his atDNA from that grandfather. 

This is an extremely small sample and the results may be distorted because results from different companies are being compared. However, I encourage you to try this at home if you have test results reflecting the difference between the atDNA inheritance patterns of sibling grandchildren. The result I report above is in accordance with what common sense would lead me to believe. If you have results that would support or refute this tentative hypothesis, I would love to see it. Maybe we all will learn something.

More Family Finder Matches?

FTDNA project administrators should be getting notices soon that announce the following changes in the threshold Family Finder customers must meet in order to be matched with each other. For those of you who like to monitor how such changes impact the number of matches you are shown, you better document your baseline data quickly. Your number of matches should change soon. 

You asked for it - we listened!

For several years the genetic genealogy community has asked for adjustments to the matching thresholds in the Family Finder autosomal test. After months of research and testing, we have implemented some exciting changes effective very soon.

Currently, the current matching thresholds - the minimum amount of shared DNA required for two people to show as a match are:

●       Minimum longest block of at least 7.69 cM for 99% of testers, 5.5 cM for the other one percent
●       Minimum 20 total shared centiMorgans 

Some people believed those thresholds to be too restrictive, and through the years requested changes that would loosen those restrictions.

Soon, the following changes will have been implemented to the matching program.

●       No minimum shared centiMorgans, but if the cM total is less than 20, at least one segment must be 9 cM or longer.
●       If the longest block of shared DNA is greater than 9 cM, the match will show regardless of total shared cM or the number of matching segments.

The entire existing database has been rerun using the new matching criteria, and all new matches have been calculated with the new thresholds. 

Most people will see only minor changes in their matches, mostly in the speculative range. They may lose some matches but gain others.  

I am assuming that most of you will get additional matches -- particularly those formed by single shared segments between 9 and 19 cMs. This will not be close relatives but potentially could be with family members in the 4th to 6th cousin range. Such matches have been suppressed because the shared cMs totaled less than 20. They can be detected in comparisons run at GEDmatch on FTDNA data.

Some die hard genetic genealogists love to analyze the changes in matches reported when adjustments are made such as the one that is imminent from FTDNA. Yesterday Jason Lee reported in a ISOGG Facebook post: "Two thirds of my matches at AncestryDNA are single segment matches under 9 cM." Those wishing to dissect the differences between databases and differences in a single database before and after screening criteria is changed will have a field day as FTDNA rolls out the above change.

If you want to be able to compare your "before" matches with the "after" ones, you better move fast. This change may start rolling out very soon.

Family Finder Gift Just Keeps Giving

Some gifts just keep giving. My Family Finder match, the one from page 51 of my match list, Family Finder finds Family Bible, has really started something. As he has shown me the way to breaking through my brick wall, I have been simultaneously exhilarated and humbled by the responses of readers on Facebook. I think my colleague from across the Atlantic, Brian Swann, hit the right note to describe my feelings when he commented, "Napoleon said the quality he prized above all in his generals was to be lucky." 

My connection with my genealogical benefactor is extremely fortuitous and also illustrates the fickleness of atDNA matches. Two of my first cousins have more significant matches with my benefactor than do I. However, for a variety of reasons which I will try to analyze later, he contacted me. 

Not only did he send me scans from the family Bible of my 2nd great-grandfather, he told me where my 3rd great-grandparents were buried. FindaGrave provided tombstone images for John, Susannah and Thomas Adams. Based on the almost identical background in each of those images and the similarity of the style of the stones, one easily could be led to assume that Thomas had a close relationship with John and Susannah even though it appears that he was more than four decades older than John. 

John Adams (1789-1849)

Susannah Adams (1792-1834)

Thomas Adams (1743-1828)

I sent a link to my recent blog post yesterday to my newly discovered third cousin -- once removed. Almost immediately I received a return email with more goodies attached. These documents seem to solidify relationships of Thomas as the patriarch of this Adams family in Madison County, John as his son and Isaac as his grandson. Previous to last month Isaac was my earliest known Adams ancestor.

Inventory of estate of John Adams conducted by Isaac Adams.

Will of Thomas Adams (page 1) which lists 4 children including John.

Will of Thomas Adams (continued - page 2)

Thank you Family Finder even if you did bury our match information 51 pages into the results. And thank you cousin for finding it anyway. Also, thanks to you and your mom for collecting and preserving these treasures. Between the information "chiseled in stone" and that is in these estate papers, I can go back even one more generation than was recorded in the family Bible.