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					DNA Mutations and Repair
Chapter 18
Part 1
Gene Mutations and Repair
   Nature of mutations

   Causes of mutations

   Study of mutations

   DNA repair
               Source of Mutations

Nuclear accidents

                       Chernobyl, April 26th, 1986
               Source of Mutations

Japan’s Tsunami disabled reactors at the Fukushima Plant March 11, 2001
Mutation: is defined as an inherited
change in genetic information by cell
division or individual organisms.
Mutations can be classified into categories.

               Categories of mutations
Somatic and germ line

Autosomal Dominant
    Gene Mutations can also be classified by type of mutation

    1. Base Substitutions

□ 2. Insertions and deletions
                 Lead to

    3. Frameshift mutations

    4. Expanding trinuleotide repeats
    Gene Mutations can also be classified by type of mutation

    Base Substitutions

                  can be

Transitions and Transversions
                   PURINE TO PYRIMIDINE
                   PYRIMIDINE TO PURINE
Expanding trinucleotide repeats
Fragile X Syndrome

Fragile X syndrome:FMR-1 gene
Update on diagnosis of fragile X
      Fragile X syndrome was originally diagnosed by
      culturing cells in a folate deficient medium and then
      assessing the cultures for X-chromosome breakage by
      cytogenetic analysis of the long arm of the X-
      chromosome. This technique proved unreliable for
      both diagnosis and carrier testing.

      The fragile X abnormality is now directly determined
      by analysis of the number of CGG repeats and their
      methylation status using:
      restriction endonuclease digestion and
       Southern blot analysis.
Strand slippage may cause repeats
Phenotypic changes and mutations
Spontaneous: slippage
                   Reverse mutation
Forward mutation
Forward versus Reverse Mutations
Terms associated with PHENOTYPIC effects of mutations on protein structure
    Phenotypic effects can also change function

    Gain of Gene Function               1

1Sullivan, J.P. et al.,
Department of Pathology,
College of Veterinary Medicine, 1998
The University of Georgia, Athens, GA

    Loss of Gene Function               2

      Qualtek Molecularlabs Web Site
Loss of Function can also occur!

        Typically recessive mutations!
Suppressor Mutations is a genetic change that hides the
            effect of another mutation
Intragenic Suppressor Mutations
Intergenic Mutation
Lethal Mutations
Do you remember something about each type of mutation?

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