Thursday, November 4, 2021

The unknown revealed

 Stanley - Thursday

Late last week, I received an email telling me something I didn't know and, quite frankly, had never thought about. To make a short story long, researchers at 23andme, one of the companies to which you can send a sample of your DNA for analysis, had tested my rs2937573 marker, which is located close to the TENM2 gene, which in turn is related to brain development. I was found to be a AA genotype. 

Translated into language I can understand, this means that I have slightly lower than normal odds of suffering from misophonia (a good word for you, Zoë!), which is a condition in which a person experiences intense anger and disgust at the sound of someone else chewing!

Good to know.

This got me to think about a related issue I have often wondered about.

A good friend of mine was given a DNA test kit as a present by his son, who had already sent his sample in. A couple of years later, the son, call him Peter, was contacted by someone, call him John, claiming to be a close relative - a half cousin, in fact. That is, Peter and John shared one grandparent.

After speaking to John, my friend concluded that John's claim was likely true and that my friend's father must have had a fling which resulted in a son - my friend's half brother, a person he never knew existed. 
Needless to say, my friend was surprised, perhaps shocked, at the revelation, because he'd always regarded his father as a man of integrity. My friend believes it is likely that his father never knew of the child he'd sired out of wedlock.

In this case, everyone lived happily ever after. My friend and his family accepted the reality of a new relative. John has never laid any claim against the estate of his grandfather or against his grandfather's heirs. As far as I know, the two families have gone back to leading their separate lives with no acrimony or anger. Perhaps part of the reason for the outcome being so benign is that the infidelity happened a long time ago, and the persons involved is no longer alive.

It is useful to know some of the facts about DNA testing - particularly when our world seems to respect facts less and less.

If you are told that you are related to someone with any of the following relationships, you can be confident that you are closely related. The only exception to this is if the DNA samples were switched, inadvertently or advertently.

Parents, children, siblings

There is an anomaly in the case of the children of identical twins. We know them as cousins, but a DNA analysis will report them as half-siblings, and both twins will be shown as parents to both sets of kids.

Second cousins or closer

There is an anomaly here too. If someone shows up as your first cousin, they could be your first cousin, but they could also be your great-grandparent or great-grandchild, half-aunt or half-uncle, half-niece or half-nephew. So, if it is important to know how someone in the first cousin category is related, a little research should sort that out.

I didn't know until researching this blog that an important word to know is centimorgan (cM) (another one for Zoë!), which is just the word that geneticists use to describe the length of DNA segments – specifically, the difference between chromosome positions.  

Every person has approximately 6800 centimorgans of DNA. This number includes both copies of each numbered chromosome, or approximately 3400 centimorgans inherited from each parent. However, siblings are likely to inherit different sets of centimorgans from their parents, because sets of centimorgans are passed down randomly from one generation to the next. This is the reason siblings are usually different. 

Here is a brief explanation of this diagram which I took from It explains how segments may be passed down.

Mike inherited an entire green segment from Grandpa. Mike's daughter still has part of the segment. Notice that Nicole's cousin, James, has no green segment.

Sam inherited light blue from Grandma and passed it to James. Mike also inherited some blue, but passed none to Nicole. also has a very useful discussion of how genes are passed down from one generation to the next, and how this frequently leads to unexpected outcomes. You can read that discussion here

DNA analysis is helpful to the police and to those of us who write mysteries. However, it doesn't take much of an imagination to conjure up heart-wrenching or traumatic situations that could be revealed by these DNA tests - issues of family, heredity, or race, not to mention likelihood of disease. I often wonder whether people sending off their DNA kits have thought of the possible implications.

A quick search of the internet reveals many stories of unexpected results, some causing great trauma, some not. Since tens of millions of tests have been performed, it is not surprising that so many people end up surprised. A good article in The Atlantic from three years ago shows some of the issues that surface. You can read it here.

I was surprised at how few reports I found of unexpected matches resulting in lawsuits, although my writer's mind came up with many.

Given the number of unexpected matches, it is not surprising that an industry has grown up to provide support. It dispenses good advice on how to handle these surprises, from preparing yourself to sharing the information with others.

Of course, people submitting their DNA have control over the extent they want the results revealed or shared. However, I suspect that most people who have paid money for the information want at least some of the information for themselves, even if they don't want anyone else to see it.

What should you know before deciding to send in a sample of your DNA?

The best advice is to read the small print from whatever company you are thinking of using for a DNA test, then decide if you are ready to handle something that could shake your views of your family. You never know what may show up. Here's a good article on how to select a company.

You should also be aware of the limitations of testing; for example of why the analysis of twin can yield different results, particularly with respect to heritage. This is a very good article on that subject.

Having your DNA tested is very appealing. However, you should be prepared for unexpected information. 

On a personal note, it was through that I found out that my British-Army-Sergeant-Major grandfather, whom we all loved and admired, was likely not married to my grandmother when he had five children. If he was married to her, it is almost certain that he wasn't divorced from his first wife. When we learnt of this, my cousins and I roared with laughter and wished that he were still alive to clarify the situation! Note: this information surfaced, not through DNA testing, but because a relative of my grandfather's first wife contacted me with the 'good' news.


  1. Genetics never fails to fascinate! It's a true wonder. I was informed by 23&Me that I have a higher than normal chance of misophonia, which would make sense, because chewing sounds make me crazy.

  2. Back in those pre-DNA days of Mendelian Genetics, my high school biology an effort to keep up the interest of his class in mitosis and meiosis.., announced that it was impossible for two blue-eyed parents to have a brown-eyed child. One brown-eyed student raised his hand and said that wasn't true because his parents were blue-eyed. The teacher stammered a bit before saying it wos obviously a mutation. The next day the student showed up and announce the teacher was correct, because he'd confronted his parents and they admitted he was adopted.

    I believe the teacher stopped using that example.

  3. Oh, gosh. Genetics is very complicated. Both my sister and I have straight hair. My father had straight hair. Yet my mother had very curly, dark hair. Neither my sister nor I had hair like that, yet curly hair is dominent. We were not adopted, for sure. I also have hazel eyes, like my father. But brown eyes are dominant, as my mother had.

    But the most surprising things I learned were that Ashkeneza Jews are considered a separate people, not called Polish or Russian. But my British and Irish ancestry is called just that.

    What is not understandable is that there are hundreds of peoples all over the world, Indigenous peoples here, in Canada and South America and the Caribbean. Then in Africa, Asia, and elsewhere.

    Also, there are Sephardic Jewish people, too. Yet they are not identified as such, but associated with their countries of origin.

    I did find distant relatives who have 2% of my shared DNA. And I found which Irish counties my relatives mainly came from, and which area of England the one great-grandfather was probably from. All fun. But nothing for the history books.

  4. Well Alan is descended from the Royal Stuarts. His DNA proved that, obvs down the paternal line. His mother however was described as a 'Roaming Romantic Gypsy.' Their DNA is Slovenian, going west through Europe, to Denmark then landing in Scotland.

    When I was interviewing that DNA specialist ( an American), he was saying that this kind of testing would force the USA into free healthcare, as the insurance companies will soon have enough Data to exclude those with presenting genotypes from having cover from that disease. Any thoughts?

  5. Under Obamacare, pre-existing conditions are covered and continue to be so, as far as I know. If the Republicans continue, to their own detriment, to try to get rid of Obamacare, and if DNA analysis continues to provide data as you suggest, insurance companies may well start denying coverage. At the moment 53% are in favour of Obamacare and 34% against so universal healthcare may come about.

  6. Obamacare, which is still in effect, does cover pre-existing diseases. If the Republicans eventually succeed in overturning it, the insurance companies may do as you suggest. However with supporters of Obamacare running at 54% and opposers at 34%, a groundswell may emerge that would end up with universal coverage. Let's hope so.

  7. I so hope for univerarl, free medical care as in Britain, Canada and a lot of other countries. A woman I know in Ottawa says she says nothing but name and symptoms going to a doctor or E.R.

    Here you give your name and insuance before saying what's wrong with you. I am told whever I go for medical care to bring my Medicare and Medigap cards with me. I could be Attila the Hun or a serial killer, but as long as I have those insurance cards, I will be seen.

    And yet, a writer-friend in England got breast cancer last year in the midst of COVID, got treated immediately and then followup. All free.