Identical And Fraternal Twins


 
 
Concept Explanation
 

Identical And Fraternal Twins

Twins are two offspring produced by the same pregnancy. Twins can be either dizygotic(fraternal twins) or monozygotic twins. Both monozygotic and dizygotic twins are known to have an increased risk of structural defects compared to the singletons. Structural defects in monozygotic twins however, are three times more frequent than among dizy­gotic twins and approximately 2-3 times more frequent than in single-tones.

Dizygotic Twins or Fraternal or Non Identical Twins

Dizygotic twins are the result of two different ova fertilized by two different sperm.Their genetic contribution is different since it comes from two different ova and two different sperm.Dizygotic twining is a common occurrence in animals.

All most of all dizygotic twins have two placentas, two chorions and two amnions, i.e., be diamniotic and di - chorionic. However, these two may fuse and look like one. The highest twining rate is seen in the black populations(Africans) and lowest in Asian populations. But dizygotic twining rate is closely related with maternal age, parity , height , weight and also on gonadotrophin levels.

Monozygotic Twins or Identical Twins

These are also called as identical twins and are the result of fertilization of one ovum with one sperm. The single fertilized  ovum then divides into two embryos, both embryos are thought to have same genetic contribution.In very rare cases, identical twins can be different sexes. These twins begin as identical male twins.

                                           

 
 
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