Fraternal twins happen when two sperm fertilize two eggs, and identical twins happen when one speed fertilizes one egg that then splits for some reason to become two zygotes.
So:
Fraternal—two eggs, different DNA
Identical—one egg, identical DNA (though it can have different epigenetic tags because nothing is straightforward)
Identical Twins = one sperm + one egg.
That egg, when dividing, breaks apart into two individual entities with the exact same dna.
Fraternal Twins = two sperm + two eggs.
This happens when two eggs are released at once and both are fertilized by two different sperm at the same time. They have different DNA.
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