• Question: why are some twins different ?

    Asked by whchloeandmag to Anil, Blanka, Cees, Emma, Mike on 2 Jul 2012.
    • Photo: Michael Cook

      Michael Cook answered on 2 Jul 2012:


      Some twins are produced when a single fertilised egg divides into two copies. These two fertilised eggs are genetically identical, so they produce identical twins.

      However, some twins are born because two eggs were fertilised separately (this is quite rare, as usually there is only one egg to be fertilised). Because two eggs are fertilised separately, they have different genetic combinations and so are nonidentical!

      I think that’s it.

    • Photo: Emma Trantham

      Emma Trantham answered on 2 Jul 2012:


      As Mike said, it’s to do with whether they are identical or non-identical.
      There are also other non-genetic factors that affect how we look so it is possible that even identical twins will look slightly different if you look really closely.

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