Services - Twin Zygosity Test

Twin Zygosity Test

A twin zygosity test is a DNA test that definitively shows whether twins are identical or
fraternal.

When twins are born, the physician usually is able to tell whether twins are identical or
fraternal by examining the placenta. Identical twins usually share a placenta, while fraternal
twins are usually in two different placentas.

However, sometimes records can be lost, the placentas might have been discarded or
damaged before twin zygosity was determined, or doubt may arise because of the twins’
physical characteristics. In such cases, only a DNA test will be able to reveal the truth. A
twin zygosity test compares the twins’ DNA profiles to see whether they match—an exact
match proves that the twins are identical.

The results of a twin zygosity test may be used to satisfy personal curiosity as well as to
help solve health problems for the twins later down the road. For example, in the event that
a twin needs an organ or tissue transplant donor, the identical twin is a perfect choice.

Identical vs. Fraternal Twins
Identical twins come from one fertilized egg, called a zygote. The zygote, which usually
develops into one child, grows and splits early in development to form two
embryos—identical twins. Because the twins come from one egg and one sperm, they have
exactly the same DNA.

Fraternal twins, on the other hand, develop when there are two different eggs in the
mother’s womb that are fertilized by two different sperms. Fraternal twins will not have
exactly the same DNA, although like other siblings, they can be expected to share some of
the DNA they inherit from both parents.

For a free consultation or to order a test, please call 1-800-My-Daddy. One of our caring,
knowledgeable case managers will review the information you provide and guide you through
the testing process.