Why do fraternal twins share up 50% of their genetics?
Your logic is correct in that there are two different eggs and two different sperm cells. These do come from the same parents, however. During meiosis, slight variations in the genetic material will occur as a result of crossing over or “recombination.” This event explains why the fraternal twins (or siblings in general) do not have exactly the same genetic material. Also, please understand that they share much more than just 50% of their genetic material. We share more than 50% with a banana!
