DNA Inheritance Is Passed Down Randomly. So Randomly That I Am 24% More Irish Than My Brother.

DNArec (1)I bet you thought that you were 100% related to your full biological siblings.

Wrong.

Siblings share, on average, about half their DNA. The reality is, however, we can actually be anywhere from 0 – 100% genetically related to our siblings! When looking at DNA test results, you could, theoretically, be totally unrelated to a sibling, though the percentage usually falls in the 50% range.

To confuse you more, your ethnicity results in an Autosomal DNA (atDNA) test can be quite different from sibling to sibling, as we each inherit unique combinations of DNA from our parents that present different parts of our genetic history.

Photo credit- www.genetics.thetech.org

DNA recombination from parents to their children. Photo credit- www.genetics.thetech.org

This stems from how DNA is passed from one generation to the next for the majority of our genome. You are unique, having received 50% your DNA from each of your parents. Your parents received 50% from each of their parents, and so on. The 50% passed to you from each of your parents was a shuffled combination of genetics so, unless you and a sibling are identical twins, you can expect your results to be different than your siblings. Recombination is purely random, so one sibling could inherit substantial chunks of DNA that the other sibling did not inherit—or vice versa. Sometimes, the differences in results can be surprising.

My brother and I each tested with AncestryDNA, a company that offers the Autosomal DNA SNP test (we have also tested with competitive companies, which offer different types of tests and differing abilities to analyze resulting data). A genealogical DNA test studies a person’s genome at specific locations, and several different types of tests are available. The Autosomal test utilizes DNA from the 22 matched pairs of autosomal chromosomes we all have, or “autosomes.” For the record, you actually have 23 pairs of chromosomes. The remaining pair, called the sex chromosome, determines your gender, male or female. An Autosomal DNA test may be taken by either a male or female, and is often used to search for relatives (on either side of the family tree), called “DNA cousin matches,” up to a maximum of 6 – 8 generations back.

The Ancestry test also provides participants a colorful pie chart, which gives you a percentage breakdown of your ethnicity by region. It is called an Ethnicity Estimate or an admixture test. Ancestry, the company, divides the world into about 25 modern reference populations, or regions, and the approximate percentage of DNA inherited from each is provided. Sections of your DNA are identified that best match the reference databases. However, the reliability of the results is dependent on a number of variables, such as comparative population size (which can be limited), the number of markers tested, and the degree of admixture in the person tested. Distinguishing between populations within continents can be difficult; as well, genetic ancestry does not respect country borders, which change often, or the migration of ancestors long ago. A person with “known” German ancestry may find zero German DNA in his/her results. This issue, most likely, is that at some point in history the ancestors of this family, who did not originate in Germany, moved to Germany and “became” German. But that does not make them genetically German.

Fortunately, as science and technology improves accuracy of the ethnicity reports continues to improve and to provide greater depth of detail. For example, results previously defined as Western European are now being broken down into subgroups such as English and French or Irish, German, etc. Results only defined as African previously are starting to break down into specific countries. Southern Europe is broken off from the Iberian Peninsula. As new algorithms are developed providing more accurate results, these improved results will show up in your account at no additional charge.

The test results for my brother and me state that we are “immediate family”—in other words, full bio brother and sister. That’s good to know! But then the results follow different paths. My brother’s DNA test results provided the following Ethnicity Estimates:

91% Great Britain; 5% Ireland; 3% Trace Regions (Italy/Greece)

According to the current AncestryDNA algorithms, my ethnicity admixture results are:

JC_AncestryDNA

My Ethnicity Estimate from AncestryDNA

37% Great Britain; 29% Ireland; 21% Europe West; 8% Italy/Greece

Since I now know that I’m 24% more Irish than my brother, I will celebrate a bit harder at St. Patrick’s Day this year!

My admixture notes a 21% Europe West contribution, which doesn’t show up in my brother’s estimates at all. Europe West is defined as primarily Belgium, France, Germany, Netherlands, Switzerland, Luxembourg, and Liechtenstein. On our maternal side, we have three lines that trace back to France and two lines tracing back to Germany. Somehow, more of our maternal line DNA was passed to me versus my brother. I guess random genetics at work.

The bottom line of those results: Ethnicity estimations remain a science that are still a bit fuzzy. Humans have moved too far over too many thousands of years for it to be reliable history of where ancestors originated. And as each parent may pass a different and variable percentage of an ethnicity down to their children, results can be surprising. So, be open minded to the results received. As well, get as many of your siblings tested as possible. Doing so opens up new insights into your full ethnicity story, as well as the possibilities of finding additional cousins.

Do you have any unusual or surprising ethnicity estimates between you and siblings? If so, let me hear about them!

45 Comments

  1. Lisa

    Hello –
    Thanks for writing this. I do not have my own experience but this helps explain a LOT as it pertains to DNA testing. I told my father that he didn’t need to do a test because his brother did it, but now I think I will go ahead and have him move forward on it.
    Thanks again – I will try to stop back and let you know how it goes!

    Reply
    1. Julie (Post author)

      Oh please do! I’d love to hear what you find out. And thanks for stopping by and commenting. It’s nice to know that my humble little blog is helping people discover their heritage.

      Reply
  2. Anne

    Beautifully explained in laymans language. Your blog post should be required reading for anyone who does the AncestryDNA ethnicity test. Apparently there have been incidents where children accused their mother of having affairs because they failed to understand the complexities of DNA. Well done.

    Reply
    1. Julie (Post author)

      I’m humbled– thank you for the kind words! I’m always happy to hear that my blog is being read, is helpful to those who stopped by, or is distributing accurate information!

      Reply
  3. Jess

    I just recently got my results and they look completely different than my brothers.. completely different regions and all..also i have 22% italy/greece and he only has 7%..
    I don’t know what to think..

    Reply
    1. Julie (Post author)

      Those percentage differences aren’t that unusual. It’s amazing how different two siblings can be.

      Reply
    2. Maureen

      Well Julie, I am amazed at how different my sister’s and my DNA are:
      SISTER: ME:
      Europe 98% 99%

      Great Britain 40% 3%
      Scandinavian 30% 12%
      Ireland 12% 34%
      Europe West 10% 48%
      Italy/Greece 4% 1%
      Iberian Pen. 1% 1%
      European Jewish <1% 0%
      West Asia Caucasus 2% 0%
      South Asian 0% 1%

      When one takes the two most common DNA origins composing the majority of our DNA, my sister is basically British/Scandinavian and I am Western European/Irish. If siblings, on average, share 50% of their DNA, we share only 39% of our DNA.

      Reply
      1. Anne

        Yours is extremely different for full siblings. While ‘possible’ it seems statistically very unlikely. I would contact the lab and explain the situation and see if they can give you a deal on a re-test. (Small percentages can be virtually ignored with these tests, and probably should be except for conversational value perhaps.)

        Reply
        1. Julie (Post author)

          Anne, thank you for your advise back to Maureen. I agree with it.

          Reply
        2. Maureen

          Thanks Anne for your comments. Ancestry did identify my sister as a first degree relative, however. I think that means a full sister… The results are surprising though. My first cousin was closer in composition to me!

          Reply
  4. Sue

    Well, I feel a bit disappointed. I had been very excited and looking forward to my results, but if it isn’t going to tell me my ethnicity I wish I had saved my money! I am super bummed. I had thought I would be able to tell my son that he had half my dna.??? But he may not? I could be Irish and my son not Irish? Guess I am just stupid. I feel like I spent a hundred bucks for something I doubt I will even look at now.

    Reply
    1. Julie (Post author)

      Oh, please look at it! Depending on what test you took, you will receive a breakdown of your ethnicity; that pie chart will provide an estimate of what locales your ancestors came from and approximately what percentage you inherited from each region. Yes, your son inherited 50% of your genetic makeup but WHAT 50% can’t be controlled. But he will still have fun learning what his own personal ethnicity is likely to be.

      Reply
      1. Tony Boisvert

        Ethnnicity is NOT a genetic trait. Ethnicity is cultural. He is just as Irish as you are, even if he has more (or less) Irish DNA than you do. The “ethnicity” breakdowns are really not about what someone’s ethnicity is, but where their ancestors are from.

        Reply
        1. Julie (Post author)

          So true. Thank you for clarifying that!

          Reply
    2. LaNell Barrett

      Yes, I wish I had sent my money for 2 tests to Hurricane Harvey victims. How absolutely worthless. 23&Me and Ancestry.com have several family surnames sand states I submitted and have completely different results than I have from here.

      Reply
  5. Diana

    We just got the results of my children, and one of our kids has more Western Europe than my husband and I combined. How can THIS happen?

    Reply
  6. Diane Board

    I’m trying to understand how my daughter is 4% Irish when I am 0% Irish and her father is <1% Irish. So.. Where did that Irish DNA come from?

    Reply
  7. Fran Christopher

    My two sons and my husband and I all tested Family Finder. The results have us very confused. The youngest has 8% Iberian. Neither my husband nor myself have any Iberian. How can we see this result in a child? His older brother does not have any Iberian. I thought one parent or the other must have Iberian to pass it to a child. Thank you for helping us with this mystery.

    Reply
  8. Jeanene

    And while having more children increases the chances of passing on more of your DNA, if you look closely, you’ll see that even with three children, not all of EDWARD and ANGELA’s DNA segments made it to the next generation.

    Reply
  9. Nigel

    Hi me and my brother recently recieved our ancestry results back through Ancestry.com
    Mine were surprising as didnt aline with the family tree recently completed.
    My brothers were more surprising making everything seem unbelievable.
    MINE/BROTHERS.
    Irish. 32 3
    English. 13 92
    West Europe. 51 2
    Finland/ Russian. 2 2
    Iberian. 1 1
    Italy. less 1
    We shared the correct amount of centimorgans for full siblings at 2551 well into the correct range.
    I asked for my brother to be retested but was denied. Was told by the branch manager that it was wothin the realms of possible but was the most diverse between full siblings he had ever seen.
    I was dissapointed they wouldn’t retest my brother as we recently lost of parents and wanted to kind of reconnect through this dna experience.
    I had read all information and literature on there website try to find an answer.
    Had a retest on myself using 23andme the results were the opposite from my ancestrydna results.
    70 British Irish.
    7.2 French German.
    16.5 Broadly Northern European.
    4.4 Scandinavia.
    1.1 Broadly European.
    .6 Southern European.
    .1 unassigned.
    Anyway its from the se region and inline with with the family tree.
    But Ancestry.com is the bigger supposedly more acurate just really confused with there results ase and my brother only have around 20% in common through ancestry.com for regions which isn’t possible correct??

    Reply
  10. Diogenes

    unless you and a sibling are identical twins, you can expect your results to be different than your siblings.

    Not even then … Doctors TV tested 3 triplets (you can google it) and the results were also all over the place

    Reply
  11. Nigel

    Hi Diogenes.
    Not sure if your reply was directed at me but i recieved it as a reply to my question.
    Doesn’t relate to my question and what you have stated is common knowledge.
    My question was the corrilation to ethnicities and centamorgans.
    I have less than 20% in common around 14% ethnicities as was retested yet we are full sibblings with the correct amount of centimorgans.
    Ancestry.com representative said we were the most diverse he had seen bordering on impossible to recieve full sibling status.
    So what if we had no common ethnicities in common can we still be full sibbings and how if taking after different ethnic dna?
    Different companies come up with different results who is most accurate?

    Reply
  12. Naomi johnson

    This article explains a lot, my brothers DNA was a lot more different than I expected. I thought the lab had got it wrong. I am 41% Irish, and my brother is 17%.

    Reply
    1. Julie (Post author)

      Thanks for letting me know that you found the post helpful!

      Reply
  13. Sharon Lanni

    I am completely perplexed after receiving my results from MyHeritage DNA. I always knew I am 100% Italian. I have my family tree with all the Italian names dating back to the 1700’s. My results: 49.8% Italian, 30.2% Greek, 14.8% Western Asia?? And 5.2% Turkey/Iran! I can understand the Greek as my mother and her family are from Sicily, but the Western Asia and Turkey/Iran makes no sense. Help, please!

    Reply
    1. Tony Boisvert

      I think it is helpful to remember that, by definition, ethnicity is not a genetic trait, but a cultural one. These DNA tests can’t measure culture, only DNA markers that tend, in the aggregate, to accompany particular ethnic heritages. So if you dig a little deeper into Italian history (long before the 1700s)—especially Southern Italy and Sicily—and also Greek history—I think you will find that the Near Eastern heritages are not actually that surprising.

      Reply
  14. Sharon Lanni

    I am completely perplexed after receiving my results from MyHeritage DNA. I always knew I am 100% Italian. I have my family tree with all the Italian last names dating back to the 1700’s. my results: 49.8% Italian, 30.2% Greek, 14.8% Western Asia?? And 5. 2% Turkey/Iran! I can understand the Greek as my Mom and her family are from Sicily, but the Western Asia and Turkey/Iran makes no sense. Help, please!

    Reply
  15. Randall Olson

    When you say you are 29% Irish….have you noticed that if you click on that number in your AncestryDNA report, it links to another page where it shows your actual Irish percentage could be anywhere from maybe 7% to 50%. The 29% they give you on the main page of your ethnicity report is just the midpoint of the possible range.

    Reply
    1. Julie (Post author)

      Very true. I was using their numbers as suggested figures from which to start my conversation!

      Reply
  16. Mary Winkler

    I am so glad I found this!!! I got my Ancestry DNA results last night and they are:
    29 % Great Britain
    26 % Italy/Greece
    16 % Scandinavian
    13 % West Europe
    12 % East Europe
    3% West Asia

    Today my sister (full sister) got hers:
    25% Great Britain
    16% West Europe
    14% Italy/Greece
    14% Scandinavian
    12% East Europe
    10% Iberian Peninsula

    My 95 year old aunt also got hers:
    32% Italy/Greece
    31% West Europe
    14% Iberian Peninsula
    11% Scandinavian
    3% Great Britain
    3% East Europe
    3% Ireland
    2% Caucausus

    I was freaked out because I don’t have Iberian Peninsula and the joke has always been that I was adopted but after reading your info, I know I just don’t have that mix. But I had no idea of British or Scandinavian heritage. I grew up believing I was German/Austrian/Italian. I need to do one of those commercials for the company. I would love your opinion on our tests. Thank you!!

    Reply
    1. Julie (Post author)

      Keep in mind that maps change all the time, and people groups have migrated throughout history!

      Reply
  17. Jeanne mckenzie

    I was wondering if every child inherits every ethnicity of their parents or is it possible not to inherit one of the ethnicities at all?

    Reply
  18. Steve

    I have a question more than a comment. MY DNA results from MyHeritage DNA percentages are: 62.2 European, 36.3 African , 1.5 American. I have always known that I was mixed race. I have curly hair and dark complexion. When I was born 62 years ago in a small community in south Alabama you were either black or white. My birth certificate says I’m white and I looked more white on my baby pictures than I do now. In the community where I live, we were called Cajuns by the white and black people. About 20 years ago we applied for Native American status, but have not been approved by some governmental branch. Most of us have lived here in the same place for generations, mainly because we were never accepted by whites or blacks. My question: In your opinion, based on my DNA results, what is my race/ethnicity and what should I tell people what I am? I get asked that sometimes when I travel outside of my community. Thank you and I have enjoyed reading your blog.

    Reply
    1. Julie (Post author)

      You can only have one race, so you would most likely claim your race as White. As for ethnicity: It is totally acceptable to claim multiple ethnic affiliations. Of your 62% European heritage, what countries are found in the list and which of those do you culturally identify with? Those are your ethnicities.

      Reply
    2. Steve

      Thank you Julie for taking time to answer my question. All of this race/ethnicity stuff is so coimplicated.

      Thanks again,
      Steve

      Reply
    3. Maureen

      Hi, Cajuns are actually Acadians who migrated to NA from France, so I don’t think that has anything to do with a darker complexion. You are a mix of European and African, lucky you. You should be proud. I would love to be less ‘vanilla’, haha

      Reply
  19. Virgil Whitaker

    Family tree DNA found that I and my blood brothter had a genetic distance of 1 on their 37 site DNA test. Possible?

    Reply
    1. Julie (Post author)

      Yes, possible. Genetic Distance doesn’t necessarily refer to a relative period of time back towards an ancestor. Is is a number of the total differences between the two tests (yours and his). You can be biological siblings and have a distance of 1.

      Reply
  20. samantha

    what is the copyright date for this paper

    Reply
    1. Julie (Post author)

      It was published here on this blog on Feb 20, 2016. Can you please let me know why you ask?

      Reply
  21. Amy Buffone

    Hi Julie! Thank you for explaining all of this. My husband, myself and our daughter had 23andMe testing done. She has ethnicity percentages that are different than each of us. He’s 80% Italian, she’s only 20%. She’s 10% French/German, I’m only 2%. He doesn’t believe that she can have such a lower percentage of Italian than he does. Thoughts? Thanks!

    Reply
  22. April

    My son and I both tested with Family Tree DNA. I came out 45% British Isles, but he came out with 0% British Isles. Is this even possible? He was also 9% Scandanavian, which I think comes from my side of the family, but I showed 0%. Something seems off to me. What do you think?

    Reply
  23. Cheri Foglesong

    That didn’t print well. Husband is the one that only has 79.6 N & W Euro and 20.4 English. SISTER IN LAW has everything else.

    Reply
  24. Leila

    I have confusing DNA results. I have had my mom and grandmother tested. Unfortunately the men in my family tree are no longer living, my father and both grandfathers (I wish these tests had been around for me to at least have tested my father…)My dad’s parents came from Finland. My maternal grandfather from Ireland.
    This is confusing for me, is if you get 50% of your DNA from your dad and 50% from your mom, how did I get such different results from my mom. She had very little Finnish and no Europe West. Did I get this all from my dad? How is this possible?
    My results were
    Finland/Northwest Russia 54%
    Europe West 26%
    Ireland/Scotland/Wales 8%
    Great Britain 7%
    European Jewish 2%
    Scandinavia < 1%
    Iberian Peninsula < 1%
    Europe South < 1%

    My Mom's were
    Great Britain 67%
    Ireland/Scotland/Wales 15%
    Scandinavia 12%
    European Jewish 1%
    Iberian Peninsula 1%
    Finland/Northwest Russia < 1%
    Europe East < 1%

    My Grandma's were
    Great Britain 73%
    Scandinavia 13%
    Europe West 7%
    Europe South 3%
    European Jewish 2%
    Ireland/Scotland/Wales < 1%
    Iberian Peninsula < 1%

    Reply
  25. Jodie

    Hi! So my entire family took Ancestry DNA. Quick question: my dad showed 9% Western Europe & my mom showed 0%. However, my brothers ancestry dna showed he was 25%. Is this possible? Maybe I’m missing something.

    Thanks in advance!
    Jodie

    Reply

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