Ask The DNA Doc


Ask The DNA Doc

These questions and answers are for information purposes only. Orchid Cellmark Inc. is not qualified to provide medical or legal advice. Please consult your physician or lawyer on such matters, as appropriate.

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Q: Can a DNA test determine who the father of a child is, if the two possible fathers are cousins?

A: Cousins are expected to share only 1/8 of their overall DNA on average. So it is highly unlikely that both of their DNA profiles would match the child's paternal DNA. However it is still ideal to test both possible fathers in a paternity test. If this is not possible, please be sure to a) test the mother of the child and b) advise the DNA testing laboratory that the other possible father is a cousin of the tested man.

Q: What do my DNA test results mean?

A: For a step-by-step description of how to interpret DNA paternity test results, go to Interpretation of DNA Test Results on our website.

Q: Can a DNA test be done using a sample from a blood glucose strip?

A: It is possible to do a DNA test using a sample from a blood glucose strip however if one is able to obtain the tissue sample used to stop the bleeding after the finger poke, that is also a good sample.

Q: I don't have any idea who my father is. Can I do a DNA test and compare my DNA profile to other DNA profiles found in a DNA database?

A: Unfortunately there is no way to determine the paternity of a child by comparing that individual's DNA to DNA profiles in a database. This is because the DNA profiles in databases are anonymous. Also, the DNA databases which are kept are incomplete - there is no single database in the world that contains a DNA profile from every person. Therefore, you will need to ask your mother or her friends to see if you can narrow down the choice of possible fathers to be tested by DNA.

Q: I had a "blood" test in 1981 to determine my paternity. The results appear to indicate that my mother could be the alleged father's child. Could this be a mistake? Can my mother and I now conduct a blood test to determine if our samples were mixed up?

A: The technology used in 1981 was likely Red Blood Cell Antigen testing or HLA testing. Neither of these technologies is used anymore for paternity testing, however both are potentially still available through the Red Cross or through a doctor. However, paternity reports are somewhat difficult to interpret so Orchid PRO-DNA would be happy to provide a free evaluation of the results before any further testing is conducted.

Q: I have DNA results which indicate that I am not the father of the child. Blood samples were collected from two of the tested parties while a cheek swab was collected from one of the parties. What is the possibility of these results being wrong?

A: DNA is the same in all cells within each individual. Therefore, even if the tested sample was blood for some individuals but cheek swabs for another, this should not affect the reliability of the tests. However as with all paternity tests, the Chain of Custody of the samples, from the moment they are taken, through to the generation of the written results, is very important. As well, the quality assurance procedures used by the testing laboratory to confirm an "exclusion" are also very important. We advise that you investigate the Chain of Custody and Quality Assurance procedures used in your case.

Q: My brother passed away over 20 years ago. At the time, he had a 9 month old child, but was unsure of the child's paternity. That child is now 20 years old. Can we test the child and me to determine paternity? The child's mother is also deceased.

A: In a case involving child and her alleged aunt, it is always best to test more than one person who is known to be related to the deceased alleged father. Possible parties include the parents of the deceased, other known siblings of the deceased or known children of the deceased. Testing these parties will allow Orchid PRO-DNA to better re-construct the possible DNA profile of your brother. If there are no other known parties available, it is possible to attempt a DNA paternal relatedness test using DNA from you and your alleged niece. However, we cannot guarantee conclusive results since aunts/uncles and nieces/nephews are expected to share only 25% of their total DNA. The actual result will depend on how much, if any, DNA you share and how common that DNA is in the general population. For more information, click here.

Q: Can DNA tell how much aboriginal blood a person has and from which First Nation?

A: Using markers that have been linked to Native Americans, some companies claim to be able to determine the amount of Native American DNA you have. However Orchid PRO-DNA does not conduct this type of test.  

Q: If a child's paternity is in question and two brothers are possible fathers, how can a DNA laboratory determine who the father is? What if only one father is tested?

A: If both brothers are tested, Orchid PRO-DNA will extend the genetic testing until we are able to distinguish between the brothers. However, if only one brother was tested, and our laboratory is not informed about the possibility of the other related alleged father, there is a possibility that the statistics we issue may not be strictly correct, because we assume that the other possible fathers are not related to the tested man. If our DNA laboratory is informed, after the testing, that a brother of the tested man might be the father, we can determine the odds that the tested man, not his untested brother, is in fact the true biological father. However, when brothers are both potential fathers of a child, we strongly recommend testing both brothers as well as the mother of the child.

Q: If DNA paternity test results indicate that a mutation is present, and there is a possibility that the true father of the child is the biological father of the tested man, what else should be done?

A: DNA paternity test results can be difficult to interpret when they involve possible mutations and/or closely related alleged fathers. The first step, if such a paternity test result is being questioned, is for Orchid PRO-DNA to conduct a free evaluation of the report. However, if there is a possibility, in any case, that a close male relative of the tested man could be the biological father of the child, it is strongly recommended that the other male relative be tested. If it is not possible to test the other possible father, Orchid PRO-DNA can still calculate the odds that the tested man is the father, as compared to the other related untested man.

Q: A DNA paternity test was conducted in 1992 by blood testing. Only one of the two possible fathers was tested. The results indicated that the tested man is the father. Is there any way the test could be wrong?

A: The "blood test" you refer to was likely an HLA (Human Leukocyte Antigen) test. This is an immunological test and is not as powerful as DNA testing. A 1986 report entitled the "Probability of Exclusion of the HLA-A, B System in North American Whites and Blacks" by R.H. Walker concluded that HLA typing has a 6.5% false inclusion rate. This means that it is possible, in 6.5% of cases, that an HLA test could incorrectly find a man to be the father. A DNA paternity test on both men will provide you with a second opinion and should address your doubt on this issue. We cannot however advise you on the legal ramifications  if, for example, the DNA test reverses the results of the previous test. 

Q: If the alleged father and mother are first cousins, does this affect the validity of DNA test results?

A: The relationships you describe are relatively far apart. First cousins, once removed, are expected to share approximately 1/16th of their total DNA on average. Unrelated persons also share close to 1/16th by chance. Thus, first cousins once removed are, in effect, unrelated. Therefore, the biological relationship you have described will have no effect on the results; however this assumes that the mother, child and alleged father are tested. We could not conduct this test without testing the mother of the child. Also, we ask that, as a precaution, you advise us of the alleged relationship between the mother and alleged father at the time of testing.

Q: Can DNA be taken from a grandmother and grandchild to determine paternity?

A: If the alleged father is deceased or unavailable, it is possible to obtain DNA from known relatives of the alleged father in a paternity case however it is not possible in advance to predict whether the results will be conclusive. In such cases, we recommend testing the mother of the child, as well as both parents of the alleged father, against the child. If only one of the paternal grandparents is available for testing, we recommend obtaining samples from known full siblings of the alleged father as well. Please click here for other options on testing without a sample from the alleged father.

Q: Can blood typing be used to determine the paternity of a child?

A: Traditional ABO Blood typing is a very outdated technique for the determination of paternity however it may be possible to exclude a man as the possible father of a child using known blood types of both individuals. Blood typing is not conclusive proof of paternity if the blood types of a man and child matched.

Q: What is the likelihood of an exclusion in a paternity test when in fact the tested man is the father?

A: Overall, the odds of a false exclusion of the true biological father of a child are extremely low when using the services of an accredited laboratory. All accredited laboratories such as Orchid PRO-DNA follow strict guidelines to ensure that reported conclusions are correct. If you have a specific example, Orchid PRO-DNA may be willing to examine previously issued reports and provide an opinion.

Q: My mother never told me who my father was. She has passed away, but I was wondering if it is possible to determine my birth father by just testing my DNA. Is this possible?

A: Unfortunately, it is impossible to test an individual's DNA by itself and determine the identity of that person's parents. It would be necessary to compare your DNA to the DNA from possible alleged fathers and/or their known offspring in order to determine if you have DNA in common with those individuals.

Q: I tested my daughter’s DNA against two possible fathers. The results indicated that one of the men is her father, but she doesn’t look anything like him. She looks like the other man. Is there a way the test can be wrong?

A: Unfortunately, physical characteristics of individuals can sometimes be misleading. It happens frequently that two unrelated individuals look alike, while in other instances, two related individuals do not share a lot of physical traits. However, if the samples from the two alleged fathers were mixed up at any time either during specimen collection or in the laboratory, then the DNA test results could be wrong. Accredited DNA testing companies such as Orchid PRO-DNA have multiple quality control procedures to ensure this does not happen. In such cases, it is important to examine the chain of custody documents completed at the specimen collection site and to question the DNA laboratory which conducted the test to determine what quality control checks were conducted.

Q: Can a relationship be established by DNA testing between 3rd cousins?

A: A 3rd cousin relationship is too far removed to test using conventional DNA testing. However it may be possible to determine if two individuals are paternally or maternally related using Y-STR or mitochondrial DNA analysis respectively. These types of tests will only be informative if the genders of the two tested individuals are suited to those procedures. For more information, please visit our Y-STR and mitochondrial DNA pages.

Q: Can you use chewing gum for DNA testing?

A: It is possible to extract DNA from discarded chewing gum as well as other non-standard samples. However results cannot be guaranteed, a non-standard Chain of Custody form must accompany the sample, and there is a surcharge for testing such samples. For more information, please go to the Non-Standard Samples page of our website.

Q: Can a DNA test be completed if the alleged father is incarcerated?

A: A DNA test can be completed if an alleged father is incarcerated (i.e. in prison or a correctional facility) as long as Orchid PRO-DNA can make arrangements for the sample to be collected. To that end, Orchid PRO-DNA will attempt to make arrangements to have the jail staff collect the sample or will send in one of our private specimen collectors to take the sample.

Q: If the alleged father lives in one province and the child lives in another province, can we still have the test done?

A: There is no requirement to have all the parties tested at the same time or same place. Therefore it is possible to test an alleged father in one province and a child in another province. However it will be necessary, if the child is underage, for the child's legal guardian to sign the consent form on behalf of the child.

Q: If DNA testing is required to settle an estate, who pays for the test?

A: If DNA test results are required by an executor or lawyer to settle the estate, then the estate usually will pay for the cost of DNA testing.

Q: Where can I get a DNA test for free?

A: Unfortunately, DNA paternity testing is not free, however you may be able to get some financial assistance by contacting your local child support or legal aid office.

Q: What if two biological brothers are both possible fathers of the same child? Do both brothers need to be tested?

A: While it is preferable to test all potential fathers (especially those who are related) at the same time, our laboratory runs a battery of tests which is typically able to exclude even a related individual who is not the biological father. However, we ask that if you are only able to test one of the brothers, you should let us know up front that the other possible father is a brother and in such a scenario, we would like to stress the importance of testing the mother of the child as well.

Q: Would the results of a DNA paternity test be more accurate if the mother of the child was tested?

A. A DNA paternity test can be conducted without the mother of the child,  however it is preferable to test the mother. By testing the mother, the laboratory can determine which half of the child's DNA came from the mother and by elimination, the remaining DNA has to come from the biological father. If the mother is tested, the probability of paternity can sometimes be higher.

Q: My DNA paternity results say that I “cannot be excluded�? as the biological father of the child. Does that mean that I am not the father?

A: In a paternity test, the possible results are an “exclusion” or “non-exclusion”. An exclusion means that the child and alleged father do not share enough DNA to be related and this would indicate that the alleged father is NOT the biological father of the child. The probability of paternity will be 0.00% in such cases. If the child and alleged father share DNA, the alleged father is said “not to be excluded” and a probability of paternity of 99.9% or higher is provided. A man cannot be found to be the biological father with 100% certainty so a result of 99.9% or higher generally indicates that the tested man is the biological father of the child.

Q: The report states that the child is not mine but my numbers match the child’s numbers. Why am I not the dad?

A: The DNA that is examined in a paternity test is shared in the general population to a certain extent. Unrelated individuals can share certain amounts of DNA. Therefore it is possible for a tested man and child who are unrelated to have some matching "alleles" (i.e. numbers).

Q: Is it possible to get a DNA test while pregnant?

A: It is possible to do a DNA paternity test prenatally using either an amniotic fluid sample or a piece of the placenta although there is a risk of miscarriage. Please consult the following link and your doctor.

Q: How soon can a sample from a fetus be taken from a pregnant woman for prenatal DNA paternity testing?

A: Depending on the type of fetal sample being collected, it can be collected typically between weeks 10-12 and between weeks 15-24. Please consult the following link and your doctor.

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