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Guilherme Mazui

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What is the Difference Between Identical and Fraternal Twins?

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The main difference between identical and fraternal twins lies in their genetic makeup and how they are formed in the womb. Here are the key differences:

  1. Formation: Identical (monozygotic) twins are formed when one fertilized egg (ovum) splits and develops into two babies with exactly the same genetic information. Fraternal (dizygotic) twins, on the other hand, are formed when two eggs (ova) are fertilized by two sperm, producing two genetically unique children.
  2. Genetic Information: Identical twins share the same genetic information, while fraternal twins share around half of their genetic information. This means that identical twins have the same DNA, while fraternal twins have different DNA, just like any other siblings.
  3. Sex: Identical twins are always the same sex, as they come from a single fertilized egg. Fraternal twins, however, may be the same gender or different genders, as they are derived from two separate eggs fertilized by two different sperms.
  4. Appearance: Identical twins may not look exactly identical due to environmental factors, but they share the same DNA. Fraternal twins may look similar, but they share only half of their genetic information, just like other siblings.
  5. Placentas: Identical twins generally share a single placenta, while fraternal twins usually have separate placentas.

In some cases, it may be difficult to determine whether twins are identical or fraternal based on their appearance or placentas alone. The most accurate way to confirm their zygosity is through a twin zygosity DNA test, which compares the twins' DNA profiles to confirm whether they match or not.

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  • What is the Difference Between Identical and Fraternal Twins?
  • Comparative Table: Identical vs Fraternal Twins

    • Comparative Table: Identical vs Fraternal Twins

    The main difference between identical and fraternal twins lies in their genetic makeup and how they are formed in the womb. Here is a comparison table highlighting the key differences between the two types of twins:

    Feature Identical (Monozygotic) Twins Fraternal (Dizygotic) Twins
    Zygosity Develop from a single fertilized egg that split into two Develop from two separate fertilized eggs
    Genetic Similarity Share the same DNA, which is about 99.9% identical Share about 50% of their DNA, similar to other siblings
    Gender Almost always the same, since they have the same DNA May be the same or different, like non-twin siblings
    Physical Characteristics Nearly identical appearances, including hair and eye color, ear shape, teeth formation, and the appearance of hands and feet May look somewhat similar, but not as alike as identical twins
    Fingerprints Unique to each twin, even though they share the same genotype Unique to each twin, even though they share the same genotype
    Amniotic Sacs May or may not share the same amniotic sac, depending on when the single fertilized egg divides Usually develop two separate amniotic sacs

    Identical twins are formed when a single fertilized egg splits into two, resulting in twins with the same genetic makeup. On the other hand, fraternal twins are formed when two separate eggs are fertilized by two separate sperm, resulting in twins with different genetic makeups.

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    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.