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Consumer Information on Genetic DNA Testing

Identical or Fraternal Twins? Twin Zygosity DNA Test

Sibling twins can be either be identical or fraternal twins. The genetic relationship between twins is referred to as twin zygosity. A Twin Zygosity DNA test can determine if your twins are indentical or fraternal by comparing their DNA profiles. Here is the basic difference:

  • Identical Twins. Occurs when an egg fertilized by a sperm cell divides into two egg cells, which then develop into identical twins. The DNA profiles of identical twins are exactly the same. Characteristics of identical twins include same sex, same eye and hair color, and similar heights and weights.


  • Fraternal Twins. Occurs when two eggs are separately fertilized by two different sperm cells that then develop in the womb. The DNA profiles of fraternal twins are not the same, they are basically siblings that are born at the same time. Physical characteristics such as eye and hair color, weight and height is often not the same, although this may be difficult to determine at time of birth. If the two sperm cells come from different males at the time of conception, the result are half-siblings.



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