What is the difference between Identical Twins and Fraternal Twins?If a woman give birth to two babies in a single delivery who are similar in all respects including their sex are known as identical twins. Even though identical twins are similar in most of their aspects they differ in their finger prints, hand writing, birth marks. In identical twin births, it is always both of them may be boys or both of them may be girls. Scientifically speaking, identical twins are caused when a fertilized egg cell split completely into two bits and each bit by repeated divisions will transform into an embryo which later grow in the uterus of the mother into two individuals. Since both the embryos are formed from the same zygote and they include the same genetic make up, the two babies will have the same sex as well as the exact similar features. Identical twins are biologically known as known as Monozygotic i.e. two individuals are produced from a single zygote.
If a woman give birth to two babies in a single delivery but they are not similar like that of identical twins are known as fraternal twins. The two babies may differ in all their features and even also in their sex. The two babies born in a single delivery may one of them may be a boy and the other may be a girl or both of them may be boys or both of them may be girls. Usually in a woman's monthly menstrual cycle only one egg will be released in every month. If this get fertilized by a sperm, there is possibility of the woman can give birth to a single individual. Rarely in a woman's menstrual cycle two eggs may be released at a time and both of them get fertilized by two different sperms leading to the development of two embryos in the mother's womb. Since the two zygotes are formed from two different eggs and two different sperms, the genetic constitution of both the individuals quite vary from each other. Hence the two individuals not only vary in their features but also may vary even in their sex except for that both of them were born at the same time with few minutes difference. Fraternal twins are biologically known as Dizygotic i.e. two individuals are produced from two different fertilized eggs.