Twin Zygosity test
To understand Twin Zygosity tests and how they might be useful, it helps to know a little bit about how twins develop in the womb. When twins are born, a doctor can say whether twins are identical or fraternal by looking at whether there is one placenta which they share or if they have a placenta each. Identical twins share one placenta, while fraternal twins have their own individual placentas.
The ‘Zygosity’ part of the Twin Zygosity test comes from how twins change from eggs to embryos in the womb. Identical twins come from one egg, known as a zygote. Usually, one zygote develops in to one baby, but sometimes a zygote splits in to two embryos instead and they become two identical twins. Because they both came from the same egg which was fertilized by the same sperm they have precisely the same DNA.
Fraternal twins are different because they come from two separate eggs and are fertilized by different sperms. Therefore, they have different DNA to one and other; their DNA has lots of similarities because they still have the same mother and father, but it is not identical. Twin Zygosity tests can be used to determine whether twins are identical or fraternal.
Usually, people just want to know the outcome of a Zygosity Test because they’re curious, especially if twins look very much alike but are believed to be fraternal. Another common reason why some people decide they want to get a Twin Zygosity test is to check how suitable one twin might be for donating an organ to the other in the event of an accident.
