• Question: Can two people who are not twins nave the same DNA

    Asked by terimater to Aime, Akshat, Diana, Gemma, Judith on 15 Jun 2011.
    • Photo: Judith McCann

      Judith McCann answered on 15 Jun 2011:

      No,Two people can have similar DNA if they are closely related (brothers/sisters) but they will never be exactly the same unless the two people are identical twins. Everyone’s DNA is a contribution from both parents, and your parents DNA is a contribution from both grandparents. This means there are tons of combinations that your DNA could be, so its statistically almost impossible to randomly get the same DNA.

      The interesting thing is DNA can be used not only to determine IF you’re related to somebody but also HOW your related to them, so a parent/child relationship would have a different amount of DNA in common that Brother/sister or cousin relationships.

    • Photo: Gemma Sharp

      Gemma Sharp answered on 15 Jun 2011:

      No two people who aren’t twins won’t have the same DNA, in fact even twins don’t have the same DNA.

      Non-identical twins have about 50% of the same DNA, which makes them no more related than any other siblings.That’s because they come from separate fertilised eggs (so two separate egg cells and two separate sperm cells).

      Identical twins come from the same fertilised egg (so one sperm and one egg), but they form in the early stages of development when the fertilised egg is dividing and multiplying. The mass of cells (called a zygote) splits and becomes two masses that develop into two babies. Although identical twins are considered genetically identical, they sometimes look slightly different, and they have different fingerprints.

      So that got scientists thinking… If they have the same DNA how come they don’t look exactly alike?

      First of all they thought it might be because of environmental things – even though they both develop in the same womb, maybe they have slightly different experiences that make their fingerprints different? Quite recently though, scientists have found that identical twins don’t actually have the same DNA… Very nearly the same! But not quite… Although they have the same genes (which are sections of DNA), one twin might have more copies of a segment of the gene than the other, and that makes the twins slightly different.

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