• Question: During meiosis, in what proportion of divisions does a mutation occur? Is this is same during mitosis?

    Asked by rebeccanesbit to Vicky, Samantha, Rachael, Matt, Karolina, Jean-Paul, Hayley, Haihan, Alison on 29 Dec 2013.
    • Photo: Vicky Forster

      Vicky Forster answered on 29 Dec 2013:


      Hi Rebecca,

      Good question! Firstly, I have to say I’m not sure if there is any difference between the mutation rate in meiosis and mitosis, but the process of DNA replication in each step is actually the same, meiosis just has an additional step, but this occurs after the division of the DNA, so i would think the rate of mutation is the same in both processes.

      Mutations will occur in every single cell division, many hundreds or even thousands of times…the exact number of mutations will depend on many things-what type of cell and also what kind of stress the DNA is under. For example, if an indvidual smokes, the cells lining their lungs will be exposed to chemicals which damage DNA and hence the mutation rate in these cells will generally be far greater than that in the cells of a non-smoker.

      However the important thing is not necessarilly rhe rate that mutations occur, but whether or not they are repaired. All eukaryotic organisms have a very complex system of proteins called DNA repair proteins, which identify and then correct and any mutations in DNA almost all of the time. However, they are not 100% reliable, and when mutations do occur in DNA, they can lead to diseases such as cancer.

      So, in summary – mutations occur all of the time, in every single cell division, but most of the time they are repaired, so do not cause any changes in DNA sequence. When these mutations are fixed in the genome, often nothing noticeable will happen as the mutation might be in what we call non-coding DNA, which has no genes in it, or a gene which isnt important in that particular cell type. However for example, if the mutation occurs in a gene in a blood stem cell which is important in blood cell growth, those cells won’t form properly and a disease such as blood cancer may result.

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