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Unformatted text preview: TYPES OF MUTATIONS 1. Base substitutions (point mutations) cause the change of one single base in the DNA. These include three categories and three possible effects: a. Missense mutation---the change in the DNA results in mRNA that codes for an incorrect amino acid in the protein that the gene gives instruction for. Even one incorrect amino acid can have a serious effect on the finished protein. An example of this is the one incorrect amino acid in two of the polypeptide chains of the hemoglobin of individuals with sickle-cell disease. This results in hemoglobin that forms crystals in the cytoplasm of the red blood cells, deforming them and making them likely to block small capillaries. b. Nonsense mutation---the change creates a stop (nonsense) codon in the middle of the mRNA molecule, causing the termination of the protein before it is finished. Since only a fragment of molecule, causing the termination of the protein before it is finished....
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