Most people know that analyzing and comparing DNA is at the heart of any paternity test. But what exactly is the science behind a DNA paternity test ? How does it work? Here’s a quick overview.
What is DNA?
DNA is everywhere. Your body contains as many as 100 trillion cells all serving important functions, from protecting your organs and carrying oxygen, to creating life through reproduction. Despite the incredible diversity of cells, each cell (except for red blood cells) shares a single important trait: a nucleus. The nucleus holds genetic information that is identical from cell to cell, bundled into molecules called Deoxyribonucleic Acid, or DNA for short.
Every cell contains the same genetic information, and every cell on your body is a potential source of DNA; skin cells, hair roots, and cells carried within saliva provide just a few examples.
Collecting DNA Samples for Paternity Testing
Paternity testing requires a clean sample (a sample free of contaminants and foreign DNA) with a good amount of the participants’ DNA. While HomeDNA Paternity can extract DNA from almost any specimen type, our standard DNA paternity test uses easy and non-invasive cheek swabs. HomeDNA Paternity customers rub the swab against the insides of their cheeks for about thirty seconds. The swab’s special mesh tip (it’s not cotton like a Q-Tip) grabs loose cells for DNA testing and typically provides more than enough DNA for a single use, such as a paternity test.
DNA Paternity Test Science: Extracting the DNA
Genetic scientists and technicians use many methods to extract DNA from cells. All methods use three basic steps:
- Lysing (breaking open) the cells
- Separating the DNA from the rest of the cell
- Collecting the pure DNA in a single sample, ready for testing
Using a special chemical process, we break open the collected cells. This separates the DNA from the nucleus and leaves the scientist with a liquid that contains DNA along with other cell parts not needed for testing, such as proteins and lipids. We then separate the DNA from the other cell parts using sophisticated robotics.
The extraction robot uses more chemicals to transfer the DNA mixture to tiny silica-based nano-beads (one billionth of a meter in size); the DNA sticks to the beads while the other cell parts are washed away.
The final step, the elution step, removes the DNA from the beads. The robot collects the pure DNA, which is now ready for the next step in the paternity testing process.
DNA Paternity Test Science: PCR – Amplifying (Copying) the DNA
The DNA scientist puts the extracted DNA into a special solution containing primers. Like toner in a biological copy machine, primers find and make copies of the DNA sample-just those specific regions that we need for a paternity test.
The copy process begins by separating the double-stranded DNA – simply by turning up the heat. As the solution cools, the primers bind to single-stranded DNA, making two copies of the original. We repeat this process (heating and cooling the DNA and the primers) 28 times, making millions of copies of tiny DNA fragments that can now be detected and viewed by a special machine called a genetic analyzer.
Scientists refer to this ‘biological copy machine’ process as Polymerase Chain Reaction, or PCR.
DNA Paternity Test Science: Measuring DNA for Paternity Testing
The complete PCR process makes copies of 16-18 Genetic Systems (sometimes called markers or loci) to make one DNA Profile: 15-17 markers useful for paternity and one (1) gender marker (used for test-participant verification). Each individual person has different sizes or lengths of DNA fragments at each Genetic System. Special software measures the different sizes of the DNA sections, represented by two numbers (alleles) at each Genetic System on your paternity test report. We then use this information to answer your paternity question.
Paternity Test Reporting
A child’s DNA Profile is always a combination of half the father’s markers and half the mother’s markers. If the tested (possible) father does not share matching markers with the child, then the tested man is excluded as the biological father (he is not the father). If the DNA Profiles do match, the father is not excluded (he is the father) and the probability of paternity is reported (typically greater than 99.99%).
Top 3 Questions about Paternity Test Results
1. Q: I got 0% probability of paternity, but the child and I still have some genetic markers that match. How does that happen?
A: It’s actually not unusual at all for there to be several matches between the tested parties, even though the alleged father and child are not related. This happens because, as human beings, we’re all bound to share some of the same genetic material. But, with the exception of a mismatch caused by a mutation, in order to be considered the biological father, the man tested and the child tested must have a match at every marker tested.
2. Q: At one genetic location, I have two numbers, but the child only has one. What does that mean?
A: Whenever there are two of the same number at one genetic location, the report shows it as just one. For example, if one of the child’s genes is 11,11 then it means they got one 11 from mom and one 11 from dad. But it shows on the report as just a simple 11.
3. Q: I tested without the mother. If she participates too, does it change the results?
A: Most likely not. But adding the mother can strengthen an inclusion (you are considered the father). For example, adding the mother could make the difference between a 99.3% probability of paternity and a 99.9% probability of paternity. Both of these are considered conclusive results.
For more information on how to understand your results see, What Do My Results Mean?
Other Types of DNA Tests
Paternity testing is a popular use for this technology, but as the science has gotten more and more sophisticated, other “lifestyle” tests have become all the rage with many consumers. There are DNA tests for ancestry, skin care, weight loss and nutrition, and even tests for dogs! It truly is a brave new world and the possibilities are endless.
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Follow us on Facebook and Twitter! If you have questions about paternity tests or other DNA testing services, please contact our Client Support Center at 888-404-4363, Mon-Fri from 8:30 AM to 5:30 PM Eastern Time. Our friendly, expert representatives are ready and happy to help. Get answers anytime by visiting our Help Center.
Gerry says
I have two children that I want to have tested all at once, can I send the tests with the other child name in place of the mother or do I have to test one child first
Identigene says
Hi Gerry,
Great question! You can send in the two children samples together, however, make sure the envelopes are properly marked as “child”. The mother is not required, but it recommended. You can always call our friendly client support and request additional swabs for the mother to be tested. Also have in mind for every person a relationship is tested, there will be an additional fee. If you have any more questions or would like to request swabs for the mother, please call us at 1-888-404-GENE, Monday-Friday 9AM-6PM ET. Thank you for your comment!
jennifer says
is a dna test different from average blood test and also ive been told that an a- and o- cant make an a+ baby im in real need of a paternity test for my son
Identigene says
Hi Jennifer,
Both tests use participant DNA that is the same whether collected by swab or blood. Buccal swabs are easier to collect and non-invasive. For more information about the difference between blood and buccal swabs, please visit this link: http://dnatesting.com/using-buccal-swabs-vs-blood-samples/
We are more than happy to help you with a paternity test for your son. Our friendly client support is available Monday-Friday 9AM-6PM ET at 1-888-404-GENE. Please contact us if you have any more questions or concerns. Thank you for your comment!
Vivian says
My sister and her (dad) took the test but the they did just eat and I believe that her dad was drinking about an hour before doing the test after putting the swabs in the envelope I noticed that they was a wet spot on the envelope and we didn’t really let it dry before touching it n the test came back saying he is not her dad but with in the test results they had a lot of matching numbers could the test have been contaminated or gotten messed up somehow and not come out right
Identigene says
Hi Vivian,
When samples become contaminated, the test cannot be continued. The samples would need to be recollected. However, since you received a conclusive result, the samples were clean and testing was able to be completed. Human DNA is very similar, it is not uncommon for some matches to occur, in order to be a complete match, there must be matches on ALL points. Anything more than three “mis-matches” is considered an exclusion. If you have anymore questions about your results, please call our friendly client support at 1-888-404-GENE, Monday-Friday 9AM-6PM ET. Thank you for your comment!
Unique Daniels says
hay is there any way that you can send me the results on a piece of paper and I noticed on your website there was no answer to my question when do I send the money, before the results or when they arrive or can I send it with the results thanks…
Identigene says
Hi Unique,
Thanks for contacting us.
Yes, please call us at 1-888-404-4363 to request this–we offer one free complimentary copy of your results.
As for your payment, you will need to pay this before testing can begin. You can do this by filling out the payment section on the order form with a credit/debit card or money order or by calling and paying over the phone with a credit/debit card. We don’t take personal checks. Hope we answered all your questions, but if you think of anything else please feel free to contact us again!
Davida Hitchcock says
How does this pertain to proving paternity in Spain? I’m an American.
Leslie Bryant says
Thank you for contacting Identigene. If you want to complete a DNA test for personal reasons, the DNA Paternity Test collection kit is perfect for you, and there are several options for sending in your samples. You may purchase a DNA testing kit from our website http://www.dnatesting.com or by calling directly 1-888-404-4363 Monday through Friday 9 a.m. to 6 p.m. E.T. The price of the test depends on the type of test you need to complete. On our website you can see of the different relationship tests we offer and the lab fee for those tests. Shipping is an additional cost and varies depending on the service you select. Additional fees may apply for shipping International each way. You can send the collection materials to each person living in another state or country so they can collect their samples, or they can simply buy their own kit to collect their samples. You can then, either have the people send the samples to you so that you can send all of the samples in at the same time, or they can be sent in to us separately. If samples are going to be sent in to our lab from separate locations, we recommend that you call us to pre-pay for the testing so that we can give you a case number to write on all of the specimen envelopes. This will help to ensure that all of the samples are linked to the same case when they arrive at our lab. You can also order a Personal DNA Paternity Test Kit directly from us over the phone and we will send kit supplies to each person directly.
If you have any additional questions or concerns, or need a legal test, or are interested in purchasing a kit directly from us, please feel free to contact us 1-888-404-4363 Monday through Friday 9 a.m. to 6 p.m. E.T. and we will be happy to assist you.
farhat joya says
I want to invite my wife to USA. I am married her for 3 years ago. Last time we had sex was 10 months ago. Does the dna test prove that she is my wife?
Meisha says
Thank you for your question Farhat Joya,
Unfortunately we do not offer any tests for proof of marriage. Our best recommendation would be to contact the embassy closest to your location and they will be able to assist you with the process you will need to follow for citizenship.
Zoie says
Hi I have a child I want to get tested how do I go about with it I need pricing on kit plus lab fees
Identigene says
Hi, Zoie. If you want a basic paternity test, the Identigene at-home kit is $21.99-29.99, depending on where you buy it. It’s available at CVS, Rite-Aid, and Walmart. This kit is for testing one child + one possible father+ the mother (her participation is optional, but recommended). Once all participants have swabbed their cheeks to collect DNA, you send samples in to our lab to have them tested. The lab fee is $119. If you need results for court, the at-home kit is not an option. Please call us directly at 800-344-9583 to make arrangements for legal testing. Hope this helps!
Amber says
In a HLA test for paternity, how likely is it that the mother of the child would match the father of the child in both the A and B ?
HomeDNA Identigene says
Hi, Amber. PCR testing has been the standard for paternity testing since the 1980s.
Lindsey says
If u tak a paternity test and it comes bak 78% does that mean u r the father
HomeDNA Identigene says
No, those are considered inconclusive results. If the possible father was tested with the child, there’s no good reason why, with today’s technology, any good lab should return inconclusive results. Additional testing should be performed to get conclusive results of 99%+ or 0% probability of paternity. You should probably contact the lab where you tested and start asking questions.