• Question: Talking about transposons and linking back to your work description: what is the function of transposons in the human body and where exactly are they found? Plus, in what exact ways are they 'moving themselves'? Thank you!

    Asked by simplymuchacha to Richard on 21 Jun 2011. This question was also asked by sarai0214.
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      Richard Badge answered on 21 Jun 2011:

      Hi simplymuchacha and sarai0214,

      Good question, I’ll deal with it in three parts:

      1) What is the function of transposons: the overall consensus is that they do not have a function in the human body as such (we do not think they are essential). They do function to make more copies of themselves, but that is all, so they are called selfish DNA. That is not to say they can’t do useful things… at least one gene that is essential for the development of your immune system was borrowed from a transposon millions of years ago – it has changed a lot but is still identifiable as such.

      2) They are found in your DNA so they are in every cell that has DNA (for example Red Blood Cells don’t have a nucleus so no DNA, so no transposons). There is some very exciting evidence that there might be more transposons in some parts of the brain, because they are moving around and making more copies, but this has not been published yet and there are still experiments to do… In general though all your cells have the same number of transposons – all together they make up 45% of our DNA. Another way to think about is is if we could take all the transposon DNA out of a human body and collect it together in one lump, it would weigh the same as a big mac (~225g).

      3) Active transposons (the ones that are moving around in living people) have genes inside them that code for proteins required to move the DNA sequence of the transposon around. This happens in two main ways – one type encode a DNA cutting and joining enzyme that goes back into the cell nucleus and finds the DNA sequence that encoded the enzyme and then cuts it out of the DNA, and then inserts in another place in the DNA. Another type has enzymes that not only can cut DNA, but also transform RNA (the information or message carrying nucleic acid) back into RNA. In this way the original DNA copy stays where it is and the RNA copy is moved somewhere else. This is the type we work on, and is the only active type known in humans.