Can my DNA Paternity Test be wrong because I’m a chimera?
Human chimeras are a popular topic for TV shows and crime scene dramas. This extremely rare and interesting genetic condition can lead to the question “Can my DNA Paternity Test be wrong because I’m a chimera?”
Named for the mythical monster with a lion’s head, a goat’s body and the tail of a snake, human chimeras have two or more genetically distinct types of cells in their bodies. This is thought to be caused by the absorption, or fusing, of twins before they are born. This would cause the chimera to carry two sets of DNA in their body. One set of their DNA and one that would have been their twin’s DNA. This second set of DNA can show up anywhere in the body. A second, distinct set of DNA may be present in the skin, blood, or even reproductive organs of the chimera. This was what happened in the case of Lynda Fairchild, profiled in the ABC documentary.
She’s her own Twin
Fairchild underwent DNA maternity testing shortly after the birth of her child. Results showed a poor match, as if she was the baby’s grandmother. It was concluded that Fairchild may have been a chimera, her body the result of the fusion of two non identical embryos at the earliest stage of development. Different parts of her body could have come from different cell lines. Further testing indicated that cells taken from her reproductive organs, contained different DNA than those taken from her mouth for the DNA testing and were a match to her children.
Though cases like this are often given a lot of press, their occurrence is very rare. No one knows exactly how many cases of human chimera there are, but most studies cite only 30 reported cases in all of human history.
What does this mean for DNA paternity testing?
An inclusion, or “positive” DNA paternity test shows that an alleged father and the child share the same DNA. Therefore that man is considered to be the biological father. The father’s DNA was passed to the child, and the loci (markers) all match up. It’s virtually impossible (that is, very, very unlikely) that possessing two sets of DNA would make someone appear to be a father when they are not. Matches at all locations indicate a positive paternity test result, even if the father is a chimera.
An exclusion (when a man is not the father of a child) could potentially be affected, by someone being a chimera. It is possible for a chimera to pass one set of DNA on to their child but show a second set of DNA with a cheek swab, as in the Linda Fairchild case. Even so, the child and the father would still likely show a partial match, similar to that of a child and an uncle, since the second set of DNA would be that of the father’s unborn twin.
I had a paternity test done by the state that i know the results were incorrect. My son is 10 and trust me I wish there was someone else. The results showed to be inconclusive, how can i see if this is what caused the results to come out incorrectly.
Hi Danny,
An incorrect paternity test result, and an inconclusive paternity test are very different things. Very, very, rarely are paternity tests incorrect. An inconclusive result simply means that the lab was not able to make a determination either way. There are many potential causes for this.
If you have an inconclusive result, I would have another test run. Since the first paternity test was done by the state, I think it was probably done with chain of custody. For the best comparison, I’d recommend you have another AABB accredited lab (like IDENTIGENE) perform a court admissible (or “Legal”) paternity test.
If the second lab cannot provide you with a conclusive result, they should be able to tell you why your paternity test result was inconclusive.
Danny, I am having the same EXACT problem. I had a test done on someone who I know for sure is the father and the test came out 99.99% inconclusive. My daughter is now 4 years old and I still haven’t been able to get another test done yet. Her father doesn’t believe that he is her father, but he was the only one I was with anywhere near conception and she looks a lot like him and his mother.
I just need a little help. I have a 14 month old daughter. I had a long time boyfriend, we broke up, i had a one night stand, then i started a relationship with another man within about a month. The last guy has already been excluded as her father so i did a dna test with my long time ex. it came back negative, but both of us agree that she looks just like him, and has nothing in common with the one night stand. is it possible that he could be a chimera? Could we just test his brother with my daughter to see if there is any relation?
@Brandi: Thanks for posting your question. I completely understand your dilemma – and that’s a tough situation – but it’s very unlikely that your “long time ex” is a chimera. Chimerism is extremely rare, with only a few documented cases in all of genetic history.
Secondly, if the paternity test shows that your ex is not the father, testing his brother won’t change the result. Testing someone related to the alleged father is always LESS conclusive than testing the father directly. In fact, these reports usually have a disclaimer such as “these results do not supersede a direct paternity test involving the alleged father.” In other words, even if an “uncle test” showed the possibility of a relationship, the direct paternity test, with its negative result, would remove all doubt.
Unfortunately, “looks” have nothing to do with it (see this article on phenotype vs. genotype). A child may “look like” a potential father (or mother) and still not be their biological child.
If you’ve tested 2 of 3 possible alleged fathers, think that they were honest in their sample collection, and received negative results for both, then the only other possibility is the third alleged father. You’re best bet is to test the third father. Even though it was a “one night stand,” he still could be the father. If you’d like to talk with us about your situation in detail, please feel free to email us or give us a call.
@mrs.joshjohnson: Are you certain the test was “99.99% inconclusive”? Usually an inconclusive result doesn’t show any percentage, since it’s inconclusive. If the test does show “99.99%” that would likely indicate that the alleged father was “not excluded” as the biological father. In other words, genetic science would consider him to be the biological father of the child because the calculations are 99.99% certain that he IS the biological father. Perhaps you can post the exact wording of the paternity test (omit names for privacy, of course) and we could help interpret. Or, you could call us and we’d be happy to review the test with you (even if it was done at another lab, we can sometimes help interpret the scientific language on the report).
Kate,
Yes, that’s what I believe it had said. I do have to get another copy of those papers, because they disappeared and I haven’t seen them for about 4 years. I’ll get back to you when I recieve those. The “scientific language” does confuse me a bit. I do know that there was a lot of excusions on the test.
Thank you so much for your reply. We are having some other tests done bc it turns out there may have been a problem with the company that did the test for us. i just really would like to know for sure who her father is and i hope it’s not the one night stand bc he is in no way interested in having a daughter, even one as cute as my angel. thanks again for your help and if you could recommend a good company for us to use that would be great. God bless.
Brandi, IDENTIGENE is an accredited lab, and can perform either a pice of mind paternity test (collected in the privacy of your home) or a legal paternity test (collected by a third party with chain-of-custody.
I’d encourage you to call on of our test consultants (1-888-988-4783) to talk about your particular situation.
i took a dna test with my oldest son but it came back excluded but they test the first person and he was not it do think i was with somebody thats is family to him
Your paternity test can only tell you if the man you tested is the father or not. It cannot provide any information regarding who the father may be.
You would need to do another test, with the other possible father(s).
I recently had a DNA paternity test, the result came back saying i am not the Biological father of the child. However i have looked through the results and there were some high score matches in the paternity index. The CRI score came back as 58, so this would mean i am related to the child however this would be impossible as i am from another part of the country and am definately not related, it would also be impossible for any of my relatives to have had any form of contact with the mother.
My scores that matched were
D16S539 – 5.35
D18S51 – 1.52
D21S11 – 2.18
D3S1358 1.05
D5S818 – 1.30
D8S1179 – 2.41
All the other parts came back 0.01 or <0.01.
The reason i believe it is possible i am a chimera is that my mother is an unidentical twin, her mother is a twin, her mothers twin had twins and i think the next generation on that side had twins as well, this tells me there is a high probabliity of twins in my family.
With those scores is it possible i am a chimera?
Hi Alex,
A CRI score of 58 does not mean that you are related to the child. Even two completely unrelated people could have that score.
If you want to more know about how paternity is calculated, you can read about it here: http://www.dnatesting.com/dna-testing/paternity-test-results.php
To answer your question, no. It’s not possible that you are a chimera. It really is an EXTREMELY rare condition. I can’t high-light this enough. It’s reported and talked about so much, because it IS so rare. And the cases of people who don’t know they are chimeras are even rarer, since this condition usually carries other health conditions and mutations which you would certainly know about.
Dear Kate,
. The second man the one i was hoping could be my father I am just wondering if he could have the rare condition (chimera) clutching at straws. he already as a daughter and see was born with her stomach organs outside her body can chimera do this ???? …….and also on 1 test it says my allel 1 CSF1PO is 11 and on the other it says it’s 10.3 thank you 
I recently had two Dna test’s done on my two alleged fathers and they both came back saying netheir are my biological father
how do u read the test
Hi Keisha,
For Paternity tests: Following paternity testing accreditation guidelines, results are reported with one of three possible statements. For example, if we tested John Doe, alleged father, and James Doe (child), our paternity test results report might say one of the following:
John Doe is excluded as the biological father of James Doe.
This means that John Doe cannot be the father of James Doe because the analysis shows that they do not share a paternity relationship.
John Doe is not excluded as the biological father of James Doe.
This means that John Doe is highly likely to be the father of James Doe because the analysis shows that they share a paternity relationship.
To see explainations on results for all tests, please go to: http://www.dnatesting.com/dna-testing/paternity-test-results.php
Dear Sarah,
Thank you very much for your question. Chimera is such a rare condition, this is most likley not the case in your situation. Most studies cite only 30 reported cases in all of human history.
I did post a blog you should read: http://www.dnatesting.com/dna-testing-blog/2010/08/can-my-dna-paternity-test-be-wrong-because-i%e2%80%99m-a-chimera/.
I really hope this answers your question. Please post any further questions you may have.
Thank you Amber
[...] DNA by taking special vitamins, drinking a lot of water, medications, or alcohol. The quesiton of “am I a Chimera” comes up often as well. (We have a wonderful post about the subject you should really take a look [...]
Hi, i am 24 years old and i gave birth to a child with down syndrome, i went to take a DNA test to determind who my child father is. They did a test by phenotypes and i was woundering if the test would be right. phenotypes look at the childs characteristic…. of course my child doesnt look like neither one of us… He has Downs… Where they supposed to give a test using genotypes? I think my child got his 3rd 21 chromosome from me. whould that make my test results inaccurate? or does Chimera have anthing to do with my case?
Hi Sharde,
We call the results “phenoytypes”, not “genotypes”, because we are reporting the data we see from the elctropherogram as the phenotype. It is a fragment length of DNA, and represents the number of repeat units at that particular locus. Because we cannot see the underlying sequence, we cannot call it a “genotype”. Your results are accurate because no one is using their external physical characteristics to determine paternity. Most likely the data at the D21 locus (D21S11) was not reported in your case due to trisomy at that locus. It is standard protocol to drop a locus in which 3 alleles are seen in any one individual.
Hi,
I am 38 years old. After many years of hearing that my father was not my father, I decided to do something about it. My mother refuse to talk about it. The alledged father is 68 years old. He said that it was a great possbility that I could be his child. He agreed to take an DNA test. The test came back “the alleged father cannot be excluded as the biological father and the probability of paternity is 99.99%. The test is confusing. I think this means that he is my father. Is there any chance or any way possible this test result could be wrong?
I do share some features with the father that raise me.
Antionette,
Thank you for your question. When the results state the alleged father cannot be excluded as the biological father and the probability of paternity is 99.99%, this does indicate that we do consider the alleged father to be the biological father. You can read more on how to read our results here: http://www.dnatesting.com/dna-testing/paternity-test-results.php.
I had a paternity test taking for court for the father, that lives in another state than me. They never showed a pic of him and i got the test back they said it was 0% chances he was the dad. I know for a fact he is the dad! so i am waiting for a pic of him that was taking at the time and they will reschedule another one to be taken. Is there anyway he can have someone else take the test that looks like him?
Hi Lisa,
The purpose of a legal paternity test is that the collector does verify identification and take photos if necessary to verify who was actually tested. The collector also signs that they witnessed the collection. My advise would be to wait for the photo to be sent to you for confirmation of who was tested. If you are still not comfortable I would then recommend doing another legal DNA paternity test with another company to verify results.
I have a 5 month old little boy. I was with this man for a while than one night i slept with his brother. This happened 2 weeks in a row. Right after that was when i found out i was pregnant. We did a paternity test throught the court with one of them and then we used the identigene for the other one. Both test came back that they were both not the father. I wasnt with anyone else and im not sure what to do at this point. ive read places that i should have them both tested at the same time and also do extensive testing. Does anyone have any advice or know what to do at this point?
Bella, You are correct. In cases like this, it’s best to do a court admissible test (with witnessed collection) on both men at the same time. It’s important that the lab have ALL the information available to them in order to provide the best calculations possible.
Hi, I am a 76 year old female who has had lots of problems during my life. I am not interested in paternity test but what is a Chimera?
I have a colon that has not worked, very bad other digestive problems, and numerous fatty tomors removed as a teenager. I have also had a CTS and they discovered that I have a cyst on my liver that was there at birth, congential.
I had a colonscopy last fall and they discovered that I have more than double the colon of an average person. That is why my colon has never worked as the doctor said because of the excess colon. It get into kinks, and nooks and crannies that cause the problems.
I was born in 1934, legally blind with nystagmus. My grandfather was an albino and I have those characterists–very fair skin with no pigment (can’t tan) My eyes are not the same. The right one sees farther away and very small and that eye is 20/400 and my left eye sees very close up and is 20/200. I can read anything with my left eye if I can get it to my nose. I was also born epelepic and spastic.
I attended regular school and have a college degree. I have worked all my life, retiring from local government in 2000 after 24 years. So I have worked hard to beat the odds.
I also was married for 7 years but am divorced. I have 4 children who range in age from 44 to 50. I have one son who is fair and looks like me but he has good eyesight. I have a daughter and two other sons who are dark haired with olive skin.
My daughter also has some other congential problems like me. She has congential cataracts and immune system diseases.
I have always felt like I was my own twin. My Grandmother was a twin and my brother has a set of twins and one of his 4 sons has a set of twins. My son who looks like me has my only two grandsons. His oldest son, was part of a set of twins and his mother lost the other twin through miscarriage.
All of these things I have researched and it is hard to find information as I think that people think that these things make one a freak. My mother always said my problems were a curse. I don’t know why, since her father, the albino came from Donegal Ireland before 1900.
Everyone who knows us says my mother wore a girdle all of her pregnancy with me and folks didn’t even know she was expecting. I always joke and say, no wonder something is wrong with me. She was even ashamed for me to go out in public when I was expecting. I had a wonderful Dad who worked with me to overcome a lot of my disabilities. He wanted me to be able to make it in the real world.
Any one got any ideas or information that they have found, or if you have some of these problems, I would like to thank you for a reply. At 76 I guess folks wonder why I would want to know, but I have worked hard to try and overcome these diabilities and lead a normal life, but I can say it has been really hard. I need to know if this has happened how will it treat my descendants.
Thanks for any feedback.
Nina
Hi Nina,
Thanks for your comment and sharing your story. It was a fascinating read. I’ll point out again, that I’m NOT a doctor, at all. Just someone interested in DNA.
In technical language: a chimera is an animal (or person) that has two or more different populations of genetically distinct cells that originated in different zygotes involved with sexual reproduction. Chimeras are formed from four parent cells (two fertilized eggs or early embryos fused together). Each population of cells keeps its own character and the resulting animal is a mixture of tissues. Chimeras are typically seen in non-human zoology, but also discovered to a rare extent in humans.
This condition is either inherited, or it is acquired through the infusion of allogeneic hematopoietic cells during transplantation or transfusion.
This is to say, a chimera is a person with two separate and distinct sets of DNA.
Albinism is caused by one of several possible genetic defects. It effects the bodies ability to produce and distribute melanin, a substance that gives color to the skin, hair and eyes. It can cause vision problems, as well as bleeding disorders, lung, and bowel diseases.
Because it is genetic, is can be passed down to your children. More information can be found here: http://www.nlm.nih.gov/medlineplus/ency/article/001479.htm
It’s great that you are thinking about how this can affect your children and grandchildren. Genetic testing is recommended for people who have a family history of Albinism. A visit with a geneticist would be a good place to start.
I recently did a DNA test with the man i believe to be the father of my child. 12 out of 16 markers match…the report says not the father.The two could pass for twins, baby pictures up to teenage look like the same person…is it possible the test is incorrect?
Hello Angie,
Because there are common DNA among the population, there are times when some markers to match. That simply indicates they are fairly common. In order to be the biological father of the child the father and child must match at each location. If there is one mismatch that could mean a mutation. In that case we would test additional markers for verification. Because there are 4 mismatches that does indicate the alleged father is not the biological father.
Hello,
I had a swab paternity test and the result came back 99.99% probability; however, my son’s blood type is A, my blood type is O, and the father’s is B. I thought it was biologically impossible for my son to have a blood type of A with his father having Type B. Is it possible? Thanks for any response.
Hello Greta,
DNA paternity tests are more accurate the blood typing test, and this is because people don’t generally know what their blood type really is for certain. I would be happy to review your case with you if you have any further questions. You may contact me directly at ashaw@identigene.com.
I’m unsure of alot of things at this point in my life, so to ANY one who can help this is my isssue… i was in a relationship for 4years with a man (never had protected sex)nor a child, we split i had met a guy an we had sex once an the condom broke, well in that time my ex an i were consitering getting back together, well a month later i found out i was pregnant she was born on dec 20th her due date was the 30th my ex an i were together on april 1, we got a dna test done but came back he is not the father, yes they look alike, ears, toes,eye color. but i know thats not the determination. but what im having a hard time with is when the lady swab she placed them in indavidal envelopes an sent it off, is that normal? the other guy will not take a test.does it matter how young my little girl was when they took the test? they have 8 out of 16 on the test, help? i really dont know what to do..
Hi Melissa,
Placing DNA samples in individual envelopes is normal. We want to keep the alleged fathers DNA samples separate from the child’s DNA samples, and sometimes collectors will place each swab in their own envelopes. However, they are usually mailed together inside the mailing address if that is what you meant. It does not matter how old the child is, there is no waiting period. 8 out of 16 markers for an exclusion is normal. Because there are markers that are very common among the population you can have some matches, however, in order for your bf to be the biological father, he has to have all markers in common with the child. The child receives one number from mom and one from dad. I hope this helps. If you do have more questions please feel free to write again or call our client support team at 888-404-4363 and they would be more than happy to answer your questions as well.
My question is, can a “chimera” or “mosaic” match the mother’s dna but not the father’s?
It is possible but not likely. These situations are very rare. In fact only a handful of reported chimera cases have ever existed. That is something that would need to be tested on the child to determine if that is what has happened.
Recently me and my son did DNA test for his immigrant visa and the test result said we do not match DNA. He did twice and both results do not match. I am really confuse now. If the result doesn’t match I can’t prove he is my son. What should I do? Is there any further and more detail test I can do to prove he is my son.
The father of my baby was just ordered to pay child support and then he asked for a DNA test. We go in 2 weeks to get it done. He is the only man i have been with in 4 years, can a test come back and say it’s not his when I know for sure it is?
If he is truly the biological father the paternity test will show that! With child support cases it’s always best to make sure its a legal collection so there can be no tampering of the samples by either party.
Michelle,
With Immigration DNA tests the collection should have been done by a collector to verify the testing lab has the correct samples from the correct people. If the test was done and the samples show there is not a match, you may want to have a second test done to confirm if you are sure the child is yours.
Hello,
I have a friend who slept with someone 5 years ago and now she has a son who is a little over 4 years old. He was conceived around the time they were sleeping together. Well, he had a Home DNA-Paternity test done 2 years ago and it came back that he was the childs father. But she has been threatening him the entire time to not tell because she has lead the other man to believe that the child is his. Now he has come out with it to the other man. So, this guy decided to have his own home paternity test done and it came back that he is the father. How could this have happened? Two tests, two different fathers? I told him he should go to a DNA facility to make sure. What do you think? Thanks.
I really need help my son is 10 years old and we took a dna test with his father and it said it was 0% Now he look just like him I keep hearing talk about he might be a chimera(my son) I was never with any one else For 2 years is there any other test we could do on my son or my son and his dad to prove to him that he is the father it is no way possible that he is not the father? Why do the test show some index match and others dont and the test exclude him cause of the onces that dont match? Please help if possible
Hi Rebecca,
The chances that your son is a chimera is very slim. I would recommend having your son and the alleged father do a legal paternity test. That way the samples are collected by a third party, ID is verified, and photos are taken in most legal collections. This will verify the DNA samples that are being tested really are from the correct participants.
Hi Jennifer,
I would recommend that the alleged father’s (both if possible) go in and have a legal paternity test completed. That way all of the samples are collected by a third party collector, ID is verified, and photos are taken in most legal collections. The collector sends the samples to the lab for testing to verify they are not tampered with by the participants. That way the lab can verify who actually sent in the samples and can test them to verify which is the correct biological father.
Amber,
I like to discuss very intresting case with you , this happend to one of my close relative and there life is misrable right now and i really need your advice what should they do to comeout from this issue. They did IVF treatment to conceive baby and after baby born they did paternity test now the Father’s dna is not matching with Baby they repeat the test but the result is same they did use home paternity kit for testing ..do you think there are some chance of DNA mutation ?
Hi Jacob,
If there were mutations anywhere in the profile, it would not be enough to exclude someone as the biological father. Mutations do happen, and when that does happen the lab has additional markers they can test in the place of the mutated marker. If the alleged father was excluded, that would indicate there are too many mismatches on the DNA profile for him to be the biological father. If he still questions it I would recommend having them complete a legal DNA test. That way the samples are collected by a collection facility, they send the samples to the lab for testing so there is no question as to the validity of the DNA samples.
I hope this helps.
It’s amazing how so many people have unprotected sex with multiple men in a short time, as it isn’t just pregnancy they should be worried about.
on the D18S51 the relationship index reads 0.0029 the child in that column is an 18 the mother is 17,18 and the father reads a 16,19 there is no match there when I went to pick up the results for the paternity test it was explained that the father was the father they asked mother and father were we related instead my other question is if the mother had sex with a guy who was albino and the child come out to be albino how could I be the father when the test read that there was a single inconsistency identified in the test?
Hello Keme,
I am not sure I fully understand your quesitons, however, I would strongly recommend calling the testing laboratory that completed the test and ask them to explain your results. If you did go through IDENTIGENE, we are always happy to speak to you about your test results and answer any and all quesitons.