• Question: As we get older our DNA mutates; Why does this happen?

    Asked by Lilyoflilyington to Carolyn, Peter, Richard, Sara, Siana on 17 Nov 2015.
    • Photo: Richard Unwin

      Richard Unwin answered on 17 Nov 2015:

      Hi Lily – great username, and great question.

      There are two reasons why our DNA may change over time, although it’s important to remember that these only change the DNA in one cell, not every cell in your body will change the same way.
      1) DNA is a long string of chemical letters. When cells divide to make 2 new cells, they have to make a complete copy of the DNA. This is done by copying the existing DNA ‘template’, and the copy is checked by special ‘proofreading’ machinery. However, when you are copying out 3 billion letters in every single one of about 30 trillion cells the odds are one may get missed and changed, and that’s a mutation.
      2) During our lifetime, cells get damaged, most often by low levels of radiation (including UV from the sun) and by reactive forms of oxygen which are made in our cells. Occasionally in a cell one of the letters can get attacked and damaged. Each cell has special machinery to recognise this damage, and either repairs that letter, or cuts it out and replaces it with a new copy of the same letter. Sometimes though, damage is missed and when the DNA is copied the wrong letter gets put into place.

      PS – Cell have another set of machinery so that if a cell gets too much damage, or can’t repair it, the cell with die so that harmful changes in the DNA are not passed on. Clever, eh?

    • Photo: Sara Falcone

      Sara Falcone answered on 18 Nov 2015:

      Perfect answer Richard.
      I can’t really add more than that.