• Question: What makes chromosomes?

    Asked by lottiemccormac to Charlie, Eoin, Jemma, Julian, Steve on 19 Mar 2011.
    • Photo: Julian Rayner

      Julian Rayner answered on 18 Mar 2011:

      Hi lottiemccormac. Chromosomes are a mixture of DNA and protein. DNA is the material that codes for life, and we usually think about chromosomes as mostly DNA. However, there are many many proteins that do a bunch of different jobs in chromosomes. Most important are histones, that fold the DNA up, like string around beads. If you looped it all out, the DNA on a chromosome would be much much bigger than the cell that it is inside, so keeping it folded is important. Other proteins in chromosomes do other jobs – making copies of the DNA when the cell wants to divide, opening bits of chromosomes up and closing them back again, when certain genes get switched on and off. Like most things in our bodies, chromosomes are much more complex and dynamic (rapidly changing) than you might initially think!

    • Photo: Eoin Lettice

      Eoin Lettice answered on 18 Mar 2011:

      Hi lottie,
      thats a great question. Information about how our bodies are made is passed from parent to children using a chemical in our cells called DNA. It’s the same for all living things – animals and plants.
      We have loads and loads and loads of this DNA in each of our cells and we need to package that down really small so that it will fit into those tiny cells.
      Chromosomes are really just made up of DNA which is wound very tightly on itself. If you take a long piece of string and wind it round itself nice and tight…. that’s kind of like what a chromosome is.
      Our cells have to unravel it before they can use it.

      Hope this helps!

      Eoin

    • Photo: Stephen Moss

      Stephen Moss answered on 19 Mar 2011:

      Hi Lottie

      Chromosomes make chromosomes! I expect you already know that our chromosomes are made of DNA, and that when a cell divides the DNA is replicated so there’s enough for the two daughter cells. In a normal non-dividing cell you wont see the chromosomes because the DNA is all in a tangled blob in the nucleus. But when a cell divides it first makes a copy of all its DNA (there are proteins to help with that) and then the DNA sorts itself out into the typical worm-like structures that you always see in pictures of chromosomes. The pairs of chromosomes then separate from one another into two identical groups, and the cell can divide.

    • Photo: Jemma Ransom

      Jemma Ransom answered on 19 Mar 2011:

      Excellent question (and finally one I can answer fully)

      A chromosome is the organised structure of DNA. If all the DNA present in a cell wasn’t tightly packed together, it would stretch for hundreds of miles (I believe it is a certain number of times around the Earth, but i’m not sure of the figure). Therefore it needs to be tightly packaged so that it fits into the tiny cell nucleus present in all of our cells (well, nearly all of them).

      Chromosomes are really important for something called gene transcription. When a cell decides it wants to make a particular protein from the DNA blueprint, it specifically unwinds the bit of chromosome that contains the DNA instructions needed to make the protein. A bit like when you want a certain piece of information from a library – you would look up the book and then open it at the correct page rather than reading every single book in the library.

    • Photo: Charlie Ryan

      Charlie Ryan answered on 19 Mar 2011:

      hi lottie thatnks for the question!
      I’m no expert but isn’t aren’t chromosones DNA (the double helix (helter skelter)) structure thing? I think DNA is made up from proteins, i think four of them. But im not so sure – try a biologist!

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