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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 Achondroplasia 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 PURINE PURINE TO PYRIMIDINE PYRIMIDINE TO PURINE Expanding trinucleotide repeats Fragile X Syndrome Pre-mutation Fragile X syndrome:FMR-1 gene Update on diagnosis of fragile X Syndrome: 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 Xchromosome. 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 Forward mutation Reverse 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 1 Sullivan, J.P. et al., Department of Pathology, College of Veterinary Medicine, 1998 The University of Georgia, Athens, GA or Loss of Gene Function Qualtek Molecularlabs Web Site 2 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?
