Twin Zygosity DNA Testing

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What is a Twin Zygosity DNA Test?

This test establishes whether twins are identical twins or fraternal twins.

  • Tests and Compares specific DNA locations for each twin
  • 100% Accurate results
  • ISO 17025 Accredited

Are they identical twins? Are we identical twins?

Two siblings carried in their mother’s womb at the same time are always referred to as twins. However, 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, this DNA test can prove whether twins are identical twins or fraternal twins.

If they are identical twins? (Monozygotic Twins)

Identical twins develop from one egg cell which has been fertilized by one sperm cell. This fertilized egg, also known as a zygote, splits during its early development, resulting in two identical embryos. (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. Therefore the DNA molecules formed within the two fertilized eggs (zygotes) are not identical. The embryos will continue to develop with their own individual DNA molecule. Therefore 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.

The Twin Zygosity DNA Test analyses the DNA profiles of the twins being tested. If the profiles are different, then the twins are fraternal, and if the profiles are identical then a probability of being identical twins is calculated.

Semi-identical twins

Half-identical twins or semi-identical twins are very rare. Also referred to as half twins, they are the result of a form of twinning where the twins inherit exactly the same genes from their mother but different genes from their father.

Even though examples of half-identical twins have been found, the exact mechanism of how they are conceived is not well-understood. It is theorised that the conception could occur in polar body twinning where sperm cells fertilize both the egg and a second egg known as a ‘polar body’.
Thus the twins are sometimes called Polar Twins.

This conception of Polar Twins is not the same as the conception of fraternal twins, in which two genetically different eggs are fertilized by two genetically different sperm. In this case, the eggs that are fertilized are genetically identical, whereas the two sperm are still genetically different.

The test for semi identical twins or Polar twins is more in depth than the twin zygosity test. Please call 0800 988 7107 to discuss this with an adviser.


Peace of Mind DNA Twin Zygosity Tests are available at all DNA Testing Clinics...Siblings

DNA Clinics recommend an appointment at one of our many DNA Testing Clinics or Pharmacies for your Twin DNA Test. Any questions you have about your chosen test can be answered on the day of your DNA sample collection. Call 0800 988 7107 to make an appointment today.


For your convenience, a DNA Clinics Nurse can visit you at home or anther location...District Nurse

If you are unable to attend an appointment for your Twin DNA Test, DNA Clinics can provide a mobile DNA sample collector to visit you at home. All mobile sample collectors are fully trained in the collection of samples for DNA Testing purposes.


Home Self-collection DNA test kits are available for your Twin DNA test...Young White Couple

DNA Clinics DNA testing kits allow you to take your own DNA samples for your chosen Twin DNA Test. Call and order a Home Kit today or visit our on-line store to order your FREE DNA Twin Zygosity test kit.



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What to do Next?

  1. Choose your preferred DNA sample collection service.
  2. For all Twin DNA tests (except on-line DNA Test Kit orders), call FREE from the UK on 0800 988 7107 to organise your appointment.
  3. Attend the appointment to have your DNA samples collected by a fully trained professional.
  4. Your DNA samples are processed in Crystal Healths accredited laboratory.
  5. You will receive your Twin DNA test results via your chosen method.


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