The offspring with similar physical appearance and getting birth together are said to be twins. Twins are of various kinds and types depending on the zygote formation and fertilization process. The fusion of female eggs with male sperms is termed as fertilization. In result of the fertilization, a zygote is formed inside the uterus of the mother, which further develop into an embryo and after completing gestation period of 9 months, the offspring (child) is delivered. Fraternal Twins and Identical twins are both are totally different from each other in their genetic and zygotic makeup. Regarding fraternal twins, two sperms fuse with two different eggs at the same time, forming two zygotes at the same time. That why they are also called dizygotic. On the other hand, a single egg after fertilization divides into two forming two embryos. That’s why identical twins are called monozygotic.
What are Fraternal Twins?
Fraternal Twins are the kind of twins that found mostly all around the world. Fraternal twins cover up over two-third total world population of the twins. Twins are the offspring that are born together at the same time. There could be a difference of minutes or hours but not more than that. Many people worldwide only consider the babies that are totally similar in physical appearance as twins, which is a totally wrong concept. Fraternal twins are the kind of twins that possess totally different physical appearance and different gender even. Fraternal twins even can have variations in their genotypes as well. Fraternal twins are born in the result of two different sperms fusing with two different eggs at the same time forming two different kinds of the zygote. In the normal cases, fertilization of one egg (female cell) and one sperm (male cell) results in the formation of a single zygote that then further develop into embryo then into a baby. In the case of fraternal twins, two different sperms fuse with two different eggs at the same time and start forming two zygotes. That’s why fraternal twins are referred as ‘Dizygotic’ as they possess two different zygotes at the same time when in the development stages. Later on, these zygotes separately develop into an embryo and complete gestation period before delivering the offspring.
What are Identical Twins?
Identical twins are the most famous and rare kind of twins that are found all around the globe without any influence of geographical area. About one-third of world’s twin population consist of identical twins. As the name depicts clearly, these twins are totally identical regarding their physical appearance as well as they possess the same sort of genotype. Although there could be minor differences in their physical appearance and that could be because of various factors such as environment etc. In the case of identical twins, there is not a fusion of two eggs with two different sperms, whereas one sperm fuses a single egg. That egg than after fusion and forming a zygote divides into two equal portions, from which each zygote part further develops into two different embryos. Identical twins have similar sort of blood groups all the time. Their nature and habits are quite similar along with their physical appearance.
Fraternal Twins vs. Identical Twins
- Fraternal Twins are formed due to the fusion of two different sperms with two different eggs at the same time.
- Identical twins are formed due to the division of fertilized egg into two forming two embryos separately.
- Fraternal twins possess different genotype, and they resemble in physical appearance but are not identical.
- Identical twins are similar regarding both genotype and physical appearance.
- Fraternal twins can possess similar or different blood groups.
- Identical twins always possess same blood group.