Biology People Science

Difference between Fraternal Twins and Identical Twins

Main Difference

The main difference between fraternal twins and identical twins is that fraternal twins two different sperms fertilize the two separate eggs whereas identical twins are prepared from a single fertilized egg that split.

Comparison Chart

Basis of DistinctionFraternal TwinsIdentical Twins
DefinitionTwins that developed from two different eggs and is fertilized in own sperm cell is denoted as fraternal twinsTwins that developed when a single egg is fertilized in one zygote is denoted as identical twins.
Development FormationIn fraternal twins, two different sperm cells fertilize the two different eggs.sThe splitting of the same fertilized egg into two
GenderUsually differentAlways the same
Genetic CodeNot identicalNearly identical
Blood typeMaybe differentAlways the same
CausesIVF, hereditary predispositionUnknown
In UteroDevelop separate sacs in uteroBNormally one utero containing one sace only

Fraternal Twins

Fraternal twins are the type of those twins that are formed as a result of two separate eggs. The another name of fraternal twins is dizygotic that can be further described as two for Di and zygote for zygotic. So collectively the word dizygotic means the combination of two eggs and sperm to form an embryo and grow in the body. As fraternal twins are formed because of two eggs and sperms, so these are called fraternal twins. These can be either of the same genders or can be boys and girls as well. According to a recent study over twins, the scientist said these are not closely related to each other in terms of DNA as compared to their other siblings. Among a lot of factors behind the birth of fraternal twins, some major ones are maternal age, heredity issues, birth control pills and all those nutrition that directly and indirectly contribute towards the chances of producing twins, triplets or multiples. All these factors can result in hyperovulation and can increase the number of one egg per cycle that ultimately increases the chances of giving birth to twins.

Identical Twins

Identical twins are those twins that although do not share the same outlook but have same DNA. These kinds of twins are not identical to each other because of multiple environmental factors like womb positioning and personal experiences after being born. The scientific reasons behind the birth of identical twins are quite simple. When a single egg is fertilized to form only one zygote and then split into two separate embryos and as a result, identical twins are born. It is easy to identify identical twins in the wombs because these share a placenta. After birth, it is hard to distinguish between identical and fraternal twins. However, these can be finding out by way of genetic test such as a twin zygosity DNA test. According to research, the overall birth ratio of identical twins across the globe is same; three in every one thousand birth. The overall characteristics of identical twins are that they always have the same gender and share the same genetic code as well. Their blood type is always the same and may be contained in one sac in utero.

Key Differences

  • The chances of fraternal twins range from six to twenty per thousand deliveries while the chances of identical twins are about three in one thousand.
  • The appearance of fraternal twins is as similar as any other sibling. The appearance of identical twins is extremely similar and may not be identical because of environmental factors.
  • The risk of TTS is low in fraternal twins while it is high in case of identical twins.
  • Fraternal twins have different gender while identical twins always have the same sex.
  • Fraternal twins are developed from two different eggs that are again fertilized by two different sperm cells. Identical twins formed because of the splitting of the same fertilized egg into two.
  • Fraternal twins have separate placentas while identical twins have the same
  • Fraternal twins have different DNA, but exactly identical as compared to the identical twins that have although the same DNA but not looked identical because of environmental factors.
  • The blood type of fraternal twins can be different, but the identical twins will always have the same blood group.
  • The reasons behind fraternal twins are IVF, certain fertility drugs, and hereditary predisposition while identical twins have not known
  • Two variations of identical twins are female-female monozygotic twins and male-male monozygotic twins. Three variations of fraternal twins are male-female dizygotic twins, female-female dizygotic twins, and male-male dizygotic twins.
  • Fraternal twins can be hereditary while identical twins need not be hereditary.
  • Fraternal twins may develop into a male-female variation while identical twins can’t develop into a male-female variation.
  • Generic codes of fraternal twins are not identical while the generic codes of identical codes are nearly same.
  • Identical twins have separate placentas, chorions, and amnions while fraternal twins will never have same amnion and chorions.
  • Identical twins may have fingerprints while fraternal twins will always have different fingerprints.
  • Identical twins will always have the same sex while fraternal twins can be the same or different sex.
  • Identical twins follow the same pattern of birth rate as compared to the fraternal that born in different rates across the globe.

Video Explanation

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