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Frequently Asked Questions (FAQs)

What is a paternity test?

A DNA paternity test is a conclusive scientific way to determine if a man is the true biological father of a child. DNA paternity testing is also often referred to simply as a DNA test, a paternity test or DNA testing.

A simple mouth swab is used to collect a small DNA sample from the alleged father and from the child (and preferably the mother) and the samples are then sent to Cellmark's specialist DNA laboratory for testing and analysis.

The same type of DNA testing can be used to establish other relationships such as maternity, sibling (brother or sister), uncle/aunt or grandparent relationships.

What is DNA?

DNA (Deoxyribonucleic Acid) is the body's genetic 'blueprint'. It is a long thread-like molecule which carries the 'genetic code' that determines our individual characteristics. DNA is found in almost all of the billions of cells that make up our body. Every child inherits a unique mixture of DNA from its parents so, with the exception of genetically identical twins, no two people in the world have exactly the same genetic code.

How does DNA testing work?

DNA testing works by detecting certain parts, or 'markers' in the DNA molecule that are known to vary greatly between people who are unrelated, but are shared by people who are related. Cellmark uses a 24 marker test (one of the markers is only found in males, and another is used to confirm gender) to compare the DNA from the people being tested and to assess their biological relationship.

The original DNA techniques for paternity testing were developed by Professor Sir Alec Jeffreys at the University of Leicester in 1984. Using this technology Cellmark became the UK’s first DNA paternity testing company in 1987. Today the technology has evolved allowing us to provide quicker, cheaper paternity tests but still with the same high levels of certainty that only DNA testing can provide.

The DNA process used today is called Short Tandem Repeat (STR) profiling, a highly sensitive process that was originally developed for forensic analysis. DNA is extracted from each mouth swab in Cellmark’s UK laboratories and the STR markers are then detected and measured. A DNA profile is the combined result of multiple STR markers. The DNA profile is shown in the test report as a series of numbers, which represent the size of the individual STR markers that have been tested.

A child inherits half of its DNA from each parent. Cellmark’s scientists will compare the STR markers in the child’s profile with the alleged parent(s) to determine if they are related. Testing will either exclude the man from paternity with 100% certainty, or will provide a probability of paternity which is usually in excess of 99.9999% (if the child’s mother is included in the test).

When carrying out a paternity test, including a sample from the mother (as well as from the child and alleged father) will always provide a more conclusive result.

Why is a paternity test more conclusive if the child's mother is included?

A child inherits half of its DNA from each parent. When the DNA profiles of a child and the alleged father are compared and analysed, the inclusion of the mother’s DNA profile allows our scientists to account for the child’s DNA which is maternally inherited. This means that it is clear which of the child’s markers have been paternally inherited and the statistical analysis of paternity is therefore more conclusive.

What is a 'Home' paternity test?

A ‘Home’ paternity test means that you can take the mouth swab samples yourself, in the comfort of your own home. This also saves the cost of paying for your samples to be taken. The samples will still need to be sent off to the laboratory for the DNA analysis and interpretation.

Home DNA testing is sometimes called ‘curiosity’ testing because although the DNA analysis is the same as in a ‘Court Approved’ or ‘Legal DNA test’, the results can only be used for legal purposes if the samples have been taken by an independent professional, such as a doctor or nurse.

How much is a DNA test?

Cellmark’s Home paternity test is priced from £99.99 + VAT.  Home DNA testing kits can be ordered from, or from Amazon or eBay.

Cellmark also provides Court Approved (also known as Legal) DNA testing.  Prices for each relationship test are provided on the website via the homepage.  A standard Court Approved paternity test, including the father, mother and child is £324+VAT (excluding sampling fees).

If I order home DNA test, when will I receive the sampling kit?

If you order a Home DNA test before 3pm, you should receive the sampling kit in the post the next day - we post out all sampling kits by 1st class Royal Mail post.

Please note that sampling kits are not sent out on a Saturday or Sunday and that Royal Mail does not usually deliver on a Sunday.

Does the home DNA test arrive in discreet packaging?

Yes. All Cellmark Home DNA kits are mailed out inside a non-branded envelope, there is no mention of Cellmark or DNA@Home on the envelope and it will be labelled ‘Private and Confidential’.

When you open the envelope it will contain a Cellmark branded folder that has all the items and instructions you will need to take the samples, together with prepaid packaging for returning the samples for testing.

What does a DNA@Home DNA test contain?

The DNA testing kit contains;

  • A folder with information about Cellmark and the DNA testing kit
  • Clear instructions about how to take the DNA samples
  • A mouth swab for each person to be tested
  • A sample collection card for each person to be tested
  • A sample declaration form for each person, requiring a signature to provide consent
  • A tamperproof, prepaid return envelope

How do I use home DNA test kit?

Detailed instructions are provided with the kit, but in summary it is very easy to take the DNA samples:

  • First complete a sample declaration form for each person being tested.  Please read more about consent here.
  • Then write the name and date of birth for each person on a collection card.
  • Next, swab each person inside their mouth to collect cells and DNA. Rub the swab on the inside of the cheeks for ten seconds.
  • Press each person’s swab firmly onto the pink section of their labelled collection card for 5 seconds (you will first need to open the collection card to reveal the pink paper). Turn the swab and press again for 5 seconds.  The pink paper will turn white where the swab has been pressed and the DNA has been transferred.  Then close the collection card.
  • Finally, place all the collection cards and the sample declaration forms in the prepaid tamper-proof envelope, seal the envelope and put it in the post to return to Cellmark.
  • The swabs should be discarded with your normal rubbish.

Watch our video to find out more

Does it matter if I can’t take all the samples at the same time?

No, once a swab has been pressed onto the collection card and the collection card has been closed, it can be stored at room temperature in the return bag until the other samples are taken. The collection card protects the DNA sample.

Once all the samples have been taken they should be returned together in the tamper evident packaging.

How long does the DNA test take?

Cellmark provides a Next Day DNA service at no extra cost.

This means that if all the DNA samples for your test arrive at our UK laboratory before 10am we aim to send the test result to you by the end of the next working day by email.

Please note that DNA testing is a complex laboratory process and very occasionally a test may take a little longer, but we are committed to getting the result to you as quickly as possible.

What if I have any other questions?

We have a team of friendly advisers who are experienced at discussing confidential matters – one of the team will be pleased to answer any questions you have about our DNA testing service. Call our customer services team free on 0800 043 1987. Mondays to Friday 8.30am-5.00pm: we have extended opening hours to help ensure that you can speak to someone at Cellmark when it's convenient for you. You can also email us at

Is relationship testing ever inconclusive?

Due to the power of DNA testing it is very rare for a paternity (or maternity) case to be inconclusive. However, very occasionally we may detect a natural change in one of the DNA markers which means that it does not match as expected.  This complicates the analysis but generally, because we test so many markers, it does not significantly impact the statistical result in cases when both parents are tested.  However, if only one parent is tested, this can lower the statistical results so that we are only able to confirm that the two individuals are closely related, rather than conclusively confirming the nature of that relationship.  

Free confidential advice

Our aim is to make arranging your home DNA test as straightforward as possible and our customer services team are on hand to provide any help and assistance you might need. Please don't hesitate to call us free on 0800 043 1987 - our friendly and experienced advisers will be pleased to answer any questions you might have about our DNA testing service.