Whenever the zygoat (fertilized egg) starts mitosis (cell division) it creates two zygoats. These two zygoats are exactly the same in looks and DNA.
Chat with our AI personalities
This is not a probability questions but a biological question and, of course, not all sets of twins are identical.
If the twins are identical, this means that a single fertilized egg split in two before it started developing into a fetus. As a result, both twins have identical genetic information. If they are not identical, then this means that two eggs were in the uterus at the same time and that they were both fertilized separately from one another. Thus they almost certainly have different genetic information.
Identical and fraternal twins typically share many similar characteristics
If they were not then they would not be called identical twins!
Identical twins are formed from a single egg that splits into two. Fraternal twins are formed from two separate eggs that are both separately fertilized. So identical twins have identical DNA, and fraternal twins do not.
Twins are not necessarily identical. They can be fraternal as well. Identical twins result when one fertilized egg splits in two. Fraternal twins result from two fertilized eggs.
They are twins!