• Question: Why can’t sections of DNA leave the nucleus? Why is it necessary to copy the instructions onto RNA? Surely there would be less risk of mistake doing that?

    Asked by chocolatecake to Louise on 22 Jun 2010 in Categories: .
    • Photo: Louise Johnson

      Louise Johnson answered on 22 Jun 2010:

      This is an incredibly good question! You’ll probably get five different answers to this one and I’m not sure of mine but here goes!

      I think this is because of what happened billions of years ago when life began. RNA is a much more useful molecule than DNA – it’s bendier, it’s more reactive, it generally *does stuffMATOMO_URL If DNA is like a message carved in stone, RNA is like a lump of plasticene pressed on to the stone to copy the message.

      RNA also has a massively important role in the cell. It’s so indispensable that most scientists think, when life first began, all genes were made of RNA. DNA was invented later because it’s better for long term storage of information. (“RNA World” is the phrase to google if you want to find out more about this on your own.)

      Even bacteria that don’t have a proper nucleus still make protein using RNA copies of their DNA, rather than direct from the DNA. So my explanation would be that all the cell’s machinery for making proteins evolved to use RNA and still does. Why hasn’t it switched to using DNA? Maybe because the RNA way works fine and a switch to DNA would be a huge change – evolution tends to go by small steps instead of huge jumps.

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