What is zygosity testing and what does it prove?
Zygosity twin testing is used to determine whether multiple children from the same birth (twins, triplets, quadruplets, etc.) are genetically identical or not. If siblings are identical, they are known as monozygotic.
This means that they were formed from a single fertilised egg, which went on to split into separate embryos and that their DNA is exactly the same.
Non-identical siblings are known as dizygotic. This means that they are the result of separate fertilised eggs and that they share half of their genes in common like other siblings.