Twins Defined

Monozygotic Twins:

Monozygotic twins which are the result of a single zygote (fertilized egg) splitting into two cell masses and becoming two individuals. The twins are genetically identical and are always of the same sex (both males or both females). Monozygotic twins are also called indentical twins.

Dizygotic Twins:

Dizygotic twins are siblings who have shared a common uterine environment. They are due to fertilization of two different ova by different sperm. Dizygotic twins are also called fraternal twins.