09 mutations

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09 mutations

  1. 1. What are they?
  2. 2. Mutations mutations – changes in the DNA 1. can have a negative resultant effect 2. can have no effect 3. can have a positive resultant effect Mutations are usually not an issue because we have two copies of each gene.
  3. 3. Mutations Mutations result in: silent mutations 2. missense mutations 3. nonsense mutations 1.
  4. 4. 1. Silent Mutations silent mutation – has no effect on the function of the cell; sequence of amino acids is not affected Often located in the non-coding (regulatory) regions. Third NT of codons can be changed yet still code for the same amino acid.
  5. 5. 2. Missense Mutation missense mutation – nucleotide sequence is changed such that a different amino acid is coded for Protein function may or may not be affected Sickle cell anemia is a result of a missense mutation.
  6. 6. Sickle Cell Anemia
  7. 7. Sickle Cell Anemia
  8. 8. 3. Nonsense Mutations nonsense mutation – nucleotide sequence is changed such that an amino acid is replaced with an early stop codon Truncated proteins are made. Most of these are digested by the cell. Nonsense mutations are often lethal at the embryonic stage.
  9. 9. Mutations Mutation types: point mutations 2. frameshift mutations 3. chromosomal mutations 1.
  10. 10. 1. Point Mutation point mutation – nucleotide changes where one base pair (bp) is replaced by another bp Point mutations are also known as substitution mutations.
  11. 11. 2. Frameshift Mutation frameshift mutations – changes in the DNA sequence which modify the translation reading frame a)deletions – removal of one or more NTs b)insertions – addition of one or more NTs
  12. 12. 3. Chromosomal Mutation Larger sections of chromosomes can break off and reattach abnormally. a)translocation mutations b)inversion mutations
  13. 13. 3. Chromosomal Mutation a) translocation mutations – large portions of DNA are exchanged
  14. 14. Translocation
  15. 15. Down Syndrome
  16. 16. Chromosomal Mutation b) inversion mutations – sections of a chromosome are reversed
  17. 17. Chromosomal Mutation
  18. 18. Fixing Mutations Enzymes are able to recognize when: nitrogenous bases are missing nitrogenous bases are fused together These mutations are detected and fixed by DNA polymerase I.
  19. 19. Fixing Mutations Enzymes recognize when bases are incorrectly paired together. These mismatch mutations are fixed by DNA polymerase III.
  20. 20. Causes of Mutations a) spontaneous errors due to enzymes b) induced errors due to mutagenic agents UV radiation  X-rays  chemical (Agent Orange)  c) transposable elements
  21. 21. Spontaneous Errors Guanine may react with water to form 8-oxo guanine 8-oxo G pairs up with adenine during replication
  22. 22. Transposable Elements Some DNA sequences naturally move themselves around the genome transposons

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