Monday, July 2, 2012

Understanding X-Chromosome Inheritance


Good Day Everyone. How is everyone doing? Fine I hope!! In this discussion, I am going to explain the inheritance pattern of the X-Chromosome in DNA Genealogy. Many people are wondering if the X-chromosome can be used in genealogical studies to predict and confirm deep and distant relationships. The answer to that is a current no. The X-chromosome behaves differently from the other chromosomes. Researchers are hard at work trying incorporate it into genealogical studies. Let's take a quick look and see what's going on with the X-chromosome. X-Chromosome Basics As you may know, humans have 46 chromosomes. The first 44 chromosomes are called the autosome chromosomes. The last two chromosomes are the sex chromosomes. The sex chromosomes are the 45th and 46th chromosome respectively. A woman has two X-chromosomes like this -> XX. A man has a single X-chromosome and a single Y-chromosome like this -> XY. One of mysterious things about the X-chromosome is that it is 3 times the size of the Y-chromosome like this -> Xy. (I used the small letter "y" to illustrate this.) In fact, according to some scientists, the Y-chromosome appears to be getting smaller over time and may eventually vanish. Watch out ladies, there may be no more men soon LOL!!!!!!!!! The X-chromosome currently should not be used in any type of deep calculations to predict or suggest distant relationships. FTDNA currently is not using it for predictions. We will see why shortly. However the X-chromosome is still analyzed. It is included in a downloadable file from both Family Tree DNA and 23andME. The X-chromosome has 18,091 SNPs and is 196cMs. For all the newbies out there, let me explain both what a SNP (snip) and cM is. SNP is pronounced "snip". DNA is composed of four bases called A, T, C, and G. A basic DNA segment would be something like this -> CATG. Now suppose a DNA sequence changes from CATG -> CATA. In this case, "G" changed to an "A". This can happen if DNA tries to copy itself and a mistake occurs. The A base is what is referred to as a SNP. The SNP is simply a base that has changed from its original value due to a copying error. Because a woman has two XX chromosomes, a woman actually has 18,091 x 2 -> 36,182 SNPs. A male has only one X-chromosome -> XY. Thus, a male has only 18,091 SNPs. cM stands for centiMorgan. A centiMorgan is a unit of measurement that's looks at the various DNA properties (DNA segments, SNPs, etc) as one. The actual defintion of a centiMorgan is a little different from what is being defined here. I purposely did that to make things easy for everyone to understand. When comparing the DNA between two or more people, the centiMorgan unit is what you want to focus on. X-Chromosome Concepts There are two basic concepts to understand when looking at the X-chromosome. Let's take a look. 1) %Inherited vs %Match - This concept can be confusing but its actually easy. There is a difference between the amount of DNA inherited versus the amount of DNA matched (shared). Suppose a mother has a total of 8 SNPs (4 T's and 4 C's) on both of her chromosome 1-> TTTT and chromosome 2-> CCCC. Remember that each of us get 50% of our parents DNA (SNPs). If the child inherits its chromosome 1 from mom, the child will get -> TTTT, which is four SNPs from mom. (The child could of inherited CCCC as well). If we compare the childs four SNPs (TTTT) to the mother's four SNPs (TTTT), there will be a 100% match!!! This makes sense, because if the mother passed all four T's to the child, then the child should match all four T's. This is what the term "50% Inherited and 100% Match" means. A father (XY) passes his entire single X-chromosome to his daugther. This means that the daugther inherits 100% of the father's 18,091 SNPs. This also means that his daugthers X-DNA is the same as his -> X(daugther)==X(father), which is a 100% match. In addition, because a father received his single X-chromosome from his mother, his daugther will automatically 100% match his mother's (paternal grandmother) X-chromosome as well. On the other hand, the father doesn't pass an X-chromosome to his son. He passes his Y-chromosome to his son. This means the son inherited 0% SNPs and is a 0% percent match. Therefore, a son will not match his father's X-chromosome. A mother with two X-chromosomes (XX) has 36,182 SNPs. Since she passes a single X-chromosome of 18,091 SNPs to her children, both a son and daugther will inherit 50% percent SNPs. This also means that either a son or daugther will match the same 18,091 SNPs, when a child compares their X-chromosome to their mother. That means a 100% match or 196cM matching. Here's a basic chart Parent Child Inherited SNPs Matched SNPs Father Daughter 100% 100% Father Son 0% 0% Mother Daughter 50% 100% Mother Son 50% 100% 2) Recombination - This term refers to a natural process that occurs when a child is being conceived. Basically what happens is that two chromosomes physically "touch" each other and exchange genetic material. Let's take an easier look. Start Touch Recombination X(Blue)--><--X(Red) X(Blue)X(Red) X(Blue/Red)<--->X(Red/Blue) Shown above is an example of recombination in a female. We start off with a blue and red X-chromosome. After the two touch each other and separate, we get two new recombined chromosomes X(Blue/Red) and X(Red/Blue). This is what happens to nearly all of our chromosomes when we are conceived. This is why we all look different. The exception of course is identical twins. Another exception is in a male between his X and Y chromosome. Remember earlier, it was stated that the X-chromosome is larger than the smaller y-chromosome. Because of this size mismatch, there is NO recombination. Start Touch No Recombination X(Blue)--><--y(Red) X(Blue)y(Red) X(Blue)<---->y(Red) This is actually why a Y-DNA test is very powerful and can extend back very far. The Y-chromosome doesn't undergo recombination. The same cannot be said for the mother. Before a mother passes one of her X-chromosomes to her children, the process of recombination occurs. Each child gets a newly recombined X-chromosome with a mixture of SNPs from the mother's parents. Here's a diagram that shows recombination in the mother. Start Recombination X(maternal)--><--X(paternal) X(maternal/paternal)<--->X(paternal/maternal) The recombination that occurs when a mother passes her X-chromosome along is why the X-chromosome can't be used for genealogical studies at this point. Let's see why!!!!!!!! Problems with X-chromosome Inheritance We now have arrived at the meat and potatoes of this discussion. Let's take a look at the reason for the current issues with the X-chromosome. The X-chromosome that's received from your mother is essentially a new X-chromosome. In fact, a brother and sister each will have a different X-chromosome that received from their mother. No matter the amount of recombination, a person still gets 18,091 SNPs from their mother. Here is the issue. Of those 18,091 SNPs you inherited from your mother's X-chromosome, there's currently no way to know how many of those SNPs are from your mother's father (maternal grandfather) or your mother's mother (maternal grandmother). There are at least two minimum scenarios.
  1. Of the 18,091 maternal SNPs, 100% of those SNPs could have come from one maternal grandparent.
  2. Of the 18,091 maternal SNPs, 50% of those SNPs could have come from each maternal grandparent.
Now you see the problem with the X-chromosome. The X-chromosome, by itself, does not always pass down 50% from one grandparent and 50% from the other grandparent. When you get your recombined X-chromosome from your mother, the mixture from her parents is not always even. Sometimes the X-chromosome will pass 100% of the SNPs from one maternal grandparent and 0% from the other maternal grandparent. In other words, zero X-DNA recombination could occur. In the discussion, I mentioned above that the X-chromosome you get from your mother is a recombined X-chromosome. This is partially true. Sometimes there is no crossover of DNA and thus no recombination will occur between both X-chromosomes in your mother. This is why you can sometimes get 100% of your X-DNA SNPs from a single maternal grandparent and zero X-DNA SNPs from the other maternal grandparent. Let's take a real life example from my personal family. Family Example 1: Possible X-Chromosome Inheritance My paternal grandmother is Juliette Turner. My grandmother's 2nd cousin is Lewis Lamar. 2nd cousins have the same great-grandparents. Their great-grandparents were Albert Johnson Sr and Savannah Lewis. I have DNA tested both my grandmother and her 2nd cousin. It turns out that both my grandmother and her 2nd cousin share 24cM of X-DNA on each of their X-chromosomes. 24cM is pretty significant. That amount of DNA is definitive of a common ancestor. The question is did they both inherit that amount of X-DNA from Savannah Lewis? To start, we are working with 196cMs of X-chromosomal DNA present in Savannah Lewis. The key is that we want to track and see if the original 196cMs of DNA in Savannah Lewis is passed down intact. Let's took a look at the two separate descent pathways from Savannah Lewis. Savannah Lewis-> Lewis Johnson-> Lizzie Kate Johnson-> Lewis Lamar (2nd cousin) If we start with Lewis Lamar's line, Savannah passed a single X-chromosome of 196cMs of DNA to Lewis Johnson. That would be a 100% match (196cM) if Lewis Johnson compares his single X-DNA to his mother Savannah. Lewis Johnson passed his only (non-recombined) X-chromosome to his daugther Lizzie Kate Johnson which is another 100% match. In fact, due to a lack of X-DNA recombination, Lizzie Kate's X-DNA from her dad would be a 100% match to her paternal grandmother Savannah. Here is the problem!! Lizzie Kate passed a recombined X-chromosome of 196cMs to her son Lewis Lamar which lowered the original 196cM from Savannah to 24cM. The question is how much of the 24cM actually came from Savannah? Some of that minimium 24cM could have come from Lizzie Kate's mother (Lewis Lamar's maternal grandmother).

During the recombination event between Lizzie Kate's maternal and paternal X-chromosomes (X[M]--><--X[P]), there may have been an exchange of DNA. If Lewis Lamar inherited a recombined X-chromosome from Lizzie Kate such as this -> X[Lizzie's mother->12cM/Lizzie's father->12cM], then part of that 24cM that he shares with his 2nd cousin, Juliette Turner, may have come from Lizzie's mother. 

In other words, Lizzie Kate's mother may have supplied SNPs to the X-chromosome that Lewis received, that are identical to what Savannah originally had. This would be a coincidental matching of DNA between Savannah Lewis and Lizzie Kate's mother, who are two unrelated people - but it's certainly possible.

On the other hand, all 24cM could have come from Lizzie Kate's father (Lewis Lamar's maternal grandfather). In the end, we have a possible range of 24cM to 196cM for Lewis Lamar. The situation is worse for my grandmother's line.
Savannah Lewis-> Valada Johnson-> Addie Ruth Hardeman-> Juliette Turner Shown above is the line of descent for my grandmother. From Savannah to Valada, that's clearly a 100% match or 196cM. Valada's X-DNA would match 100% to the X-DNA of her mother Savannah. The problem immediately comes in when Valada passes a possible recombined X-chromosome to her daugther Addie Ruth. Some of Savannah's original 196cM could of gotten lowered to at least to 196cM-xcM or more. The problem is we don't how much of the 196cM-xcM at Addie Ruth's level's is Savannah's. Addie Ruth's maternal grandfather, Albert Johnson Sr, may have contributed SNPs to the 196cM-xcM that may coincidentally match SNPs that were originally present in Savannah Lewis. If we proceed on down to my paternal grandmother, Addie Ruth passes a recombined X-DNA to Juliette Turner. We again don't know how much of Savannah's is present in the final 24cM that was detected in Juliette. Juliette's maternal grandfather, Vines Hardeman, may have removed and supplied X-DNA SNPs that were identical to what Savannah Lewis originally contributed. Therefore Savannah's original contribution may have been further lowered!!!! So to answer the question - Is the 24cM from Savannah Lewis? The answer is that at this time it's unknown. All 24cMs could be from Savannah Lewis. At this point, there is no tool that exists that can reliably trace back to verify. As one can see, a maternal grandparent can contribute unknown cMs (percentages) that coincidentally may match what another maternal grandparent originally had. If that's the case, then one cannot say that the entire 24cMs is from the ancestor in question (Savannah Lewis). We would have to show that none of Lewis Lamar or Juliette Turner's maternal grandparents, who are outside the line of descent from Savannah Lewis, made any contribution to the shared 24cMs of X-DNA. No one as of yet has been able to design an algorithm that can make consistent predictions based on the X-chromosome's haphazard mode of inheritance. The autosome chromosomes don't exhibit this mode of inheritance. Off the bat, it's known that a person receives 50% from each parent, 25% from grandparents, 12.5% from great-grandparents, etc. Essentially, the autosomal DNA amounts are "summed up" before hand, and an algorithm can be based on that. Let's take a look a 2nd example from my family with a larger shared X-DNA amount. Family Example 2: Possible X-Chromosome Inheritance My mother is Muriel J. Mitchell. My mother's first cousin is Lonette Fay Lanier. Muriel and Lonette are first half cousins. Both Muriel and Lonette shared the same grandmother - Annie Elizabeth Mitchell (1884-1938). It turns out that Lonette and Muriel share 58.8cMs of X-DNA. The question we want to ask is this: Is the 58.8cM of shared X-DNA from Annie Elizabeth Mitchell? To answer this question, we want to look at both Muriel and Lonette's line of descent from their grandmother - Annie Mitchell. To begin, we start off with 196cM of X-DNA in Annie Mitchell. Annie Elizabeth Mitchell -> Ulysses C. Mitchell -> Muriel J. Mitchell From Annie Mitchell to her son Ulysses, we have a passing of a single X-chromosome of 196cM. Ulysses Mitchell is a 100% match to his mother Annie Mitchell. Ulysses Mitchell then passes his only non-recombined X-chromosome of 196cM to his daugther - Muriel J Mitchell. Muriel is a 100% match to Ulysses AND to her paternal grandmother - Annie Elizabeth Mitchell as well. This is because there was no recombination (no exchange of X-DNA) that occurred between X and Y chromosome within Ulysses Mitchell. Therefore all of Muriel's X-chromosomal DNA is from her paternal grandmother. However 58.8cMs of that 196cM matches Lonette. Let's take at Lonette's line of descent to answer our question. Annie Elizabeth Mitchell -> Nancy Lula Proctor -> Lonette Fay Lanier Annie Elizabeth Mitchell passes a single X-chromosome of 196cMs of DNA to her daugther - Nancy Lula Proctor. This is a 100% match if Nancy compared her X-chromosome to her mother - Annie Mitchell. Nancy then passes a recombined X-chromosome of 196cM to her daugther - Lonette Lanier. Of that shared 196cMs of X-DNA, 58.8cM matches Muriel Mitchell. The problem is that Lonette's maternal grandfather - Charles A. Proctor - may have removed and then supplied SNPs to the shared 58.8cMs of X-DNA. By coincedence, Lonette's maternal grandfather - Charles Proctor - may have supplied SNPs that may match what originally was present on Annie Mitchell's X-chromosome. If that's true, then all of the shared 54cMs of X-DNA is NOT from Annie Mitchell. We would have to show that Lonette Lanier is a 100% match to her maternal grandmother to prove that the shared 58.8cM of X-DNA is from their grandmother - Annie Mitchell. In the end, Muriel and Lonette share 58.8cMs of X-DNA that all could be from Annie Mitchell. To makes things interesting - let's throw my line of descent into the mix as Lonette and myself share 58.3cMs of X-DNA. (Lonette Lanier-> X-58.3cM <-Steve Handy Jr.) Annie Elizabeth Mitchell -> Ulysses C. Mitchell -> Muriel J. Mitchell -> Steve Handy Jr Continuing from above - Muriel passes a recombined X-chromosome of 196cM to myself. Of that 196cM - I share 58.3cM of X-DNA with Lonette Lanier. The problem is that my maternal grandmother - Odessa Ridgeway - may have replaced and supplied SNPs to my maternally inherited X-chromosome. Odessa Ridgeway may have supplied SNPs on my X-chromosome that were identical to what Annie Mitchell orignally contributed. If that's true, then all of the shared 58.3cM of X-DNA is NOT from Annie Mitchell. In my line of desent - there are two potential maternal grandparents of mine that could of contributed to the shared 58.3cM of DNA between me and my cousin Lonette. We would have to show that none of those maternal grandparents made any contribution to the 58.3cM of X-DNA. Given the X-chromosome's unpredictable mode of inheritance, that's currently not possible to do. It's easy to assume that a large amount of X-DNA is from a shared ancestor - but with the X-chromosome - it's not always as simple as that. There's one more concept that needs to be touched on before ending the discussion - coincidental matchings. IBS and Noise Someone once said the truth is stranger than fiction. Indeed this is the case in this final discussion. It's logical to think that two or more people who share DNA are automatically related. In reality, this is partially true. Living things may share DNA due to simple chance and coincidence. For example, a bird and bat both have wings. However they both evolved those structures in two separate and independant lines. IBS stands for Identical By State. It's a term that essentially means a matching of DNA via chance or coincedence. Noise is simply IBS that's created by the DNA test itself. Noise is simply a reflection of the imperfection inherent in any man made tool or test. Noise and IBS appear frequently in X-chromosomal matchings. For example, remember that a father never passes an X-chromosome to his son. Thus, there would be a 0% matching between the X-chromosomes between a father and son. However, due to noise, it can be shown an X-chromosome matching between a father and son, say at 3cM, can occur. Clearly that would be noise and should be ignored accordingly. Well that's it for basic X-chromosome inheritance. Basically if you want to use the X-chromosome, then the most it can be used for is 1st or 2nd generation predictions and matchings. An example of where the X-chromosome can be used in genealogical studies is between two female cousins whose fathers are siblings. (Each father must have the same mother) Each female cousin's paternal X-chromosome is a 100% match to their shared paternal grandmother. This is because there is zero recombination between the X and Y chromosomes of the father. The father simply passes a non-recombined X-chromosome to his daughter. That non-recombined X-chromosome has the entire 196cMs of X-DNA which is passed down intact from the cousin's paternal grandmother. If both female cousins share, say 100cMs of X-DNA, then clearly that shared amount of X-DNA is from their shared paternal grandmother. Beyond the grandparents, the X-chromosome simply is not a reliable genetic structure that can be used at this time. This is due to the X-chromosome's unpredictable mode of inheritance. Hopefully in time, our understanding of the X-chromosome's mode of inheritance will improve. This may lead to an algorithm that can based on it and thus the X-chromosome can be used in deep genealogical studies. As always, it been a pleasure to serve and help you Thanks Steve Handy

37 comments:

  1. Thank you Steve, this is the clearest explanation I've read concerning the interpretation of the X chromosome.

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    1. You are quite welcome Deb. The X-chromosome should really only be used below the grandparent level - which is max at the first cousin level. Past first cousins - the X-chromosome shouldn't be used except in certain unique cases.

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    2. You are like a freaking genius. I love learning...I think I was excited and got a headache from overload of information. You explained that well!!!

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    3. I'm trying to determine if someone is my aunt or my half-sibling. I have narrowed down this woman to being on my father's side and using gedmatch, we match 196.1 out of 196.1 on the X and the autosomal match is 1783 cm. Does the possibility still exist that she is anything other than a half-sibling?

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    4. I'm trying to determine if someone is my aunt or my half-sibling. I have narrowed down this woman to being on my father's side and using gedmatch, we match 196.1 out of 196.1 on the X and the autosomal match is 1783 cm. Does the possibility still exist that she is anything other than a half-sibling?

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    5. Hi brighterDayz - a female's X-chromosome is a 100 percent match to her paternal grandmother. The only other relationship would be a grandparent sharing 1783cM

      Of course it would easy to rule out a grandparent- grandchild relationship due to age

      Hope that helps
      Steve

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    6. I have found a person that shares 3586.9 cm (autosomal) & 196.1 X DNA does this mean I have a Twin? I noticed that the most possible autosomal cm's are 3587 and X DNA is 196 what does this all mean? On the graphics it shows 22 chromosomes all with solid green & blue lines except on chromosome 1 & 7 a exceptionally small red line (only visible on 100% resolution) & on chromosome 11 two small red lines . Just wanting to know as my mind has been running wild with theories that my twin &'I being separated at birth or something this was all found thru gedmatch

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  2. Great article and easy to follow!

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  3. great article. I think your article explains a question I had. I did a dna study on a relative. this person is admixture (60% black, 40% European). the x chromosome painting showed about 80% European, 10% middle eastern, 10% African. I was surprised because generally, adminixtured populations in the Americas show a stronger African influence in the X chromosome (which matches the historical fact of European men mating with afro or Native American women). So, what's happening in this particular case? is it by chance that this particular person inherited most information from a white grandparent? THis person's mom was most likely white? What's your thought?

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  4. Wow, quite informative. I have an X match that is 35 cM. But from your article I shouldn't even bother getting excited. It was by far and away the largest cM of any match on 23andme. Can I use it if we also share another chromosome match that is greater than 7 cM? Or should I look elsewhere for connections?

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    1. Hi Shane. How are you? Because you are a male - it's clear that the X-DNA is on your mom's side. Past your mom - it's very difficult to pin down a shared common by X-chromosome alone. I would focus on more autosomal matchings since those have a consistent and predictable pattern on the generations.

      Hope that helps
      Steve

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  5. Steve, what do you think about a mtDNA match where ONLY X is shared and no other chromosomes?

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  6. I'm in the same boat as German Magnolia - I've a match on ONLY X, two segments of 40.2cM and 13.7cM. 23andme suggests we're 4th cousin but we're having trouble finding the link.

    Should we be looking further back, or not at all?

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  7. Thank you! Excellent explanation. I did not understand this at all until I read your blog.

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  8. If I match someone on the 'x' chromosome and also match them on other chromosomes, is this a paternal or maternal match?

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  9. I find this article utterly confusing.

    You wrote:
    "Savannah passed a single X-chromosome of 196cMs of DNA to Lewis Johnson. That would be a 100% match (196cM) if Lewis Johnson compares his single X-DNA to his mother Savannah. Lewis Johnson passed his only (non-recombined) X-chromosome to his daugther Lizzie Kate Johnson which is another 100% match. In fact, due to a lack of X-DNA recombination, Lizzie Kate's X-DNA from her dad would be a 100% match to her paternal grandmother Savannah."

    and:

    "Annie Elizabeth Mitchell passes a single X-chromosome of 196cMs of DNA to her daugther - Nancy Lula Proctor. This is a 100% match if Nancy compared her X-chromosome to her mother - Annie Mitchell. "

    Shouldn't both Lizzie Kate's and Annie's X-chromosomes be a recombination of both their parent's X-chromosomes, i.e. not 100% of Lizzie Kate's from her father, and not 100% of Annie's from her mother?

    From what I understand is the DNA recombines within the egg when it is fertilized. if it's a boy it doesn't recombine, the X and Y remain separate. It's a girl it gets blended together. While the female fetus develops in the womb this new combination is given to her eggs in various combinations as the it matures into a baby girl, who will be born with most of her eggs formed and "programmed". The baby girl will be born with a 50/50 mix of her parents DNA, but her eggs will not necessarily pass along that 50/50 mix to her children.

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    1. No!!! Not with the x-chromosome. The amounts are not always even as with the autosome chromosomes. You don't always get even amounts. The x-chromosome has a different inheritance pattern than the autosomes.

      None of the DNA companies do a x-chromosome way because it's inheritance pattern is not straightforward and predictable as the autosomes are.

      Hope that helps

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  10. I recently found a match with a near 100% match on an X chromosome. We have no significant (7cM or more) matches anywhere else. If I'm understanding everything, it means we trace back, paternally, to a single woman, with all the descendants tracing down from that woman being male? Basically, if we both trace our paternal lines back, son to father to grandfather, etc, we'd end up at the same woman?

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    1. Nooope, that's all wrong (duh, males don't pass an X to their sons). Somehow, the X didn't do any sort of recombination after being passed down that long, or it's a total fluke that we share that much on the X and nothing of substance anywhere else.

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  11. I am not a biologist, so I think this is complicated. We have a special project going on in our community where we have DNA-tested some 50 people. We have tests both of myself (a man) and a first cousin of mine, her name is May. My mother Dagny was the sister of May´s father, Georg. Our common grandmother was Trine, our common grandfather was Ole. We get a strong match on the X-chromosome, in fact 149.3 cM. I must have inherited 100% of my X-chr. from my mother Dagny, and May got her X-chr. from both her parents. Her father Georg got all of his X-chr. from Trine. Doesn´t our strong match on the X-chr. mean mean that this match must come Trine?
    Reidar O. Meling, Bømlo, Norway

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  12. The main focus concerns the diagnosis of hereditary diseases
    Every paternity establishes a special relationship. This not only means a lifelong emotional bond, but also includes extensive and ongoing legal obligations. As large as the scope of that relationship is, the questions can be just as excruciating if there are any doubts about the Paternity Test, DNA Relationship Test and Identity Proofs. Unlike the mother, as a general rule, the father is naturally often left with his suspicions unless he decides to take a paternity test.

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  13. Very Good! Still seems very relevant more than 3 years after you wrote this.

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  14. Question. My tests show only a small amount of Italian but my father is mostly Italian . I can't have him tested so trying to find threw geno what I inherit from him. Is it even possible to only carry 2.4% of your fathers ancestors line?

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  15. I see that this post is a couple of years old, so I'm not sure if anyone will see my question. I am very new to DNA ancestry research. I have uploaded my Ancestry results to GEDmatch, and I feel as if I'm just fumbling through, trying to figure it out. In regards to the X-DNA results. The results show matches with nearly all other females. Some of the X matches have low autosomal matches as well, but the others only show an X match. The highest X results is around 27-28 cMs. Can these results help me figure out if they are paternal or maternal matches. Also, with the few male X matches...do these results help me figure out which side of the family to look at?
    Thanks!

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  16. The answer is far more complicated. In short, if you share X and no autosomal DNA with the person, they could match hundreds and hundreds of years back. You can find more info on how to proceed at DNAAdoption.com--the methodology there helped me find my mom's birth parents, and she was born in 1930!

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  17. Thanks Angie,
    I will look at the suggested site. One more question if you don't mind...If I match both the x and autosomal, but the x result is higher...does that make a difference in figuring out which side of the family I should look at? It's difficult because I do not know much about my dad's family. He never knew his dad, but through my research...I have figured who is father was. I was hoping that my DNA results could confirm 100%.

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  18. It depends. If you are female, you could have gotten that X from either parent. If you are male, only from your mother.

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  19. Hello, I believe that I have found a half sibling but I have a question. We are both females and she has a known father who is an only child.I have an unknown father. We share 2036.2 cM autosomal and 195.8 cM on X-DNA per gedmatch. Grandparent relationship is ruled out due to age. Would you consider this a niece or half sibling relationship? Related mothers is ruled out.

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  20. How many segments (not counting X) that are 7 cM or larger? Where are you getting the data?

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  21. I have summerly the same almost, but with 3 family members?

    Autosome total. XDNA 196.1
    3587.1 Largest 281.5
    3586.9. Largest 281.5
    3587.1. Larest 281.5

    Gen 1

    What does: Value shown is estimated genrations to MRCA

    Mine is from GenMatch too.

    I only put in for Autosome, and not xDNA or YDNA, so i am also lost and new at this DNA stuff, hmmmm.

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  23. You're comparing it to your own data or you're looking at a parent/child.

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