Twin DNA Testing

Twin DNA Testing, or Zygosity testing, is a type of DNA test to determine if twins are identical or not. Also, the same applies to triplets. So, Zygosity testing covers all children from the same birth, not only twins.

There is great interest in Twin DNA Testing these days, and not only for curiosity. For instance, there are practical reasons for finding out if you or your children are identical twins. Here’s some examples:

  • To adapt your approach when treating siblings as individuals.
  • To assess the likelihood of conceiving twins again.
  • When asked to take part in any research about multiple births.
  • Last, while it might seem obvious, you have the answer ready when asked “Are you/they identical?”

How Twin DNA testing works

Two siblings carried in their mother’s womb at the same time are always referred to as twins. Yet the twins can either be identical twins or fraternal twins. The Twin DNA test can prove whether you, or your children, are identical or fraternal twins. By comparing the DNA profiles of each twin, we can determine if twins are identical or fraternal.

So, we can use this DNA Test to answer the following questions:

  • Are my twins identical or non-identical?
  • Am I an identical or non-identical twin?


If they are identical twins? (Monozygotic Twins)

When one egg cell is fertilized by one sperm cell, identical twins develop. This fertilized egg, also known as a zygote, splits during its early development, resulting in two identical embryos. In other words, they are from a single fertilised egg which then split into separate embryos.  Also, as the twins have developed from one zygote, they are often referred to as monozygotic twins.  The embryos will continue to develop into identical twins. The DNA of identical twins is exactly same, so they will have identical DNA profiles.


If they are Fraternal twins? (Dizygotic Twins)

Fraternal twins develop from two separate egg cells fertilised by two separate sperm cells. The DNA of each egg cell and each sperm cell varies. Thus, the DNA formed within the two fertilized eggs (zygotes) are not identical. The embryos will continue to develop with their own individual DNA molecule. So, the fraternal twins will have different DNA profiles. (As the twins have developed from two separate zygotes, they are often referred to as dizygotic twins.) The DNA profiles of fraternal twins can be as different as the profiles of any two siblings that are not twins.  In other words, they only share half of their genes in common like other siblings.


How accurate is the Twin DNA Test?

We use the DNA samples taken from mouth swabs to generate a DNA profile for each twin. The Twin DNA Test analyses the DNA profiles of both twins. If the profiles are different, then the twins are fraternal. Conversely, if the profiles are identical, then we will calculate the probability of identical twins, usually at 99.99% accuracy.


How do I order a Twin DNA Test?

There are many options available to you, these include:

  • Order a free Twin Test kit from our online store*
  • Call to make an appointment at one of our DNA Clinics
  • Call to arrange for a sample collection technician to visit your location


Why choose DNA Clinics for your Paternity Test?

  • DNA Clinics is a brand partner of Boots
  • Processing of all Twin DNA Tests is in a UK laboratory with UKAS accreditation
  • A standard turnaround of only 3-5 days for Twin Test results
  • Established in 2005, our team of experts will guide you through the science
  • Unrivalled convenience with a choice of over 50 DNA Clinics nationwide
  • Certification to 3 ISO standards. This includes Quality, Information Security and Environment standards
  • We are a registered company with the Information Commissioner’s Office


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