Why are some twins identical and some not?
Identical Twins
There are two types of twins –
1. Identical or monozygotic twins
2. Non-identical or dizygotic twins
The monozygotic or identical twins are formed by cleavage in one zygote, that is, only one fusion took place between an ovum and a sperm, a single fertilization. After this fusion, the zygote formed gets cleaved into two equal halves, leading to the formation of two identical twins. Since they are formed from a single fertilised ovum, they have the same variations and, thus, they appear alike.
The dizygotic twins are formed by the fusion of two different ova with two different sperm in a single pregnancy. This fusion leads to the formation of two different zygotes, and hence, two non-identical twins are formed. These non-identical twins can be of the same or different sexes, depending on the fusion of sperm.
This was the basic difference between identical and non-identical twins. I hope this helps.
– Written By Manpreet
