• Question: why is RNA different to DNA and why are there two cell instructions when the DNA already contains the genetic meterial?

    Asked by arfs532prey79 to Precious O, emmabull, Alicia M on 31 Mar 2026.
    • Photo: Alicia Montulet

      Alicia Montulet answered on 31 Mar 2026:

      DNA is much more stable than RNA. That allows it to be stored safely, tucked away in the nucleus so that they’re is an intact version of the genetic material. RNA is slightly different structurally, the additional oxygen it has can react with the link that connects all it’s smaller components (the nucleotides or bases) and be broken down. This means that once the genetic instructions are copied to RNA and the instructions are used to make a protein (RNA also has many other functions), the RNA can be broken back down to it’s nucleotides and reused to make copies of the other instructions that are needed!

    • Photo: Emma Bull

      Emma Bull answered on 1 Apr 2026:

      Hi, fantastic question!

      Lets picture that you’ve just bought yourself a super complex Lego set that builds an entire town. It contains thousands of bricks and once you’ve finished, you will have made multiple different buildings, streets, parks, transport and more. Can you imagine how big the instruction booklet would be and how many pages it would have? It would probably be broken down into sets of instructions for how to make each separate building and type of transport right, because the instructions that we need to make the beds, TV and fridge to go inside a house are definitely not needed inside a train are they!

      This is very similar to our DNA. Our DNA is like the big instruction book containing every single instruction needed to make every single part of us. And its the same inside every different part of our body. The cells that make our muscles don’t actually need the instructions on how to make teeth, or hair, or our eyes. And our skin doesn’t need to know how to make the acid that digests the food in our stomach, or how to make fingernails. This is where our RNA comes in. RNA is small copies of specific DNA instructions that are needed in a particular place, a bit like photocopying only the instructions to make the TV from the huge instruction book when you are making a house.

      But when building our city, we don’t want to fill every house with just thousands of TVs, we would need a sofa to sit on and a bed to sleep on and an oven to cook with… Once we have made a TV we can chuck away the copy of those instructions, and copy the instructions for a sofa, and then for a bed, toilet, fridge, carpet etc. But if we need a new sofa one day, we can just recopy from the big instruction book and make a new one. Our cells do the same. They can destroy the RNA instructions once they are finished with them, and then recopy them next time they need them. But if they destroyed the DNA itself, they would destroy the main copy of instructions and not be able to repair themselves ever again, like throwing away the main book of instructions and then accidentally breaking part of the lego model.

      Our body is like the whole city, and all the different buildings are the different organs like our heart and lungs and stomach and bones and skin. Our DNA is the master copy of all instructions needed in the entire city, and our RNA is copies of small numbers of instructions that are needed at particular times or in particular organs.

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