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Point Mutations

by Georgina Cornwall, PhD
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    00:00 Let us look at some of these single nucleotide mutations. They can manifest themselves in a number of different ways. The first option is that absolutely nothing changes. It is not even in a coding region, so it doesn't matter. But if you were in a coding region, then a number of things could happen. First of all, let us look at a silent mutation.

    00:22 In a silent mutation, we have a one base change that does not result in any change of amino acid. You will recall there is some redundancy in the genetic code, so we're still coding for prolene and everything is okay. That mutation is silent. But if we have a base change in which we start coding for a different amino acid, we'll result in a missense mutation. This one we had in the second position of the triplet code, we definitely are causing a different amino acid to be added to the chain and this may or may not have a large effect depending on whether it is still a polar amino acid or nonpolar amino acid whether it has an impact on protein folding. The final thing is what if we have a base substitution that results in a stop codon. Clearly we then have a truncated polypeptide chain, which is likely to not be functional. A nonsense mutation means that it creates a whole bunch of nonsense and it is not a functional protein. That is just looking at


    About the Lecture

    The lecture Point Mutations by Georgina Cornwall, PhD is from the course DNA Repair & Genetic Mutations.


    Included Quiz Questions

    1. Mis-sense mutation ----- change in the structure of a chromosome
    2. Transition ----- replacement of a purine base with another purine
    3. Transversion ----- replacement of a purine with a pyrimidine
    4. Silent mutation ----- codes for same amino acid
    5. Non-sense mutation ----- premature stop codon

    Author of lecture Point Mutations

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD


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