Biochem mutations

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Biochem mutations

  1. 1. Mutations
  2. 2. What Are Mutations? <ul><li>Changes in the nucleotide sequence of DNA </li></ul><ul><li>May occur in somatic cells (aren’t passed to offspring) </li></ul><ul><li>May occur in gametes (eggs & sperm) and be passed to offspring </li></ul>
  3. 3. Are Mutations Helpful or Harmful? <ul><li>Mutations happen regularly </li></ul><ul><li>Almost all mutations are neutral </li></ul><ul><li>Chemicals & UV radiation cause mutations </li></ul><ul><li>Many mutations are repaired by enzymes </li></ul>
  4. 4. Are Mutations Helpful or Harmful? <ul><li>Some type of skin cancers and leukemia result from somatic mutations </li></ul><ul><li>Some mutations may improve an organism’s survival (beneficial) </li></ul>
  5. 5. Types of Mutations
  6. 6. Chromosome Mutations <ul><li>May Involve: </li></ul><ul><ul><li>Changing the structure </li></ul></ul><ul><ul><li>of a chromosome </li></ul></ul><ul><ul><li>The loss or gain of part of </li></ul></ul><ul><ul><li>a chromosome </li></ul></ul>
  7. 7. Chromosome Mutations <ul><li>Five types exist: </li></ul><ul><ul><li>Deletion </li></ul></ul><ul><ul><li>Inversion </li></ul></ul><ul><ul><li>Translocation </li></ul></ul><ul><ul><li>Nondisjunction </li></ul></ul><ul><ul><li>Duplication </li></ul></ul>
  8. 8. Deletion <ul><li>Due to breakage </li></ul><ul><li>A piece of a chromosome is lost </li></ul>
  9. 9. Inversion <ul><li>Chromosome segment breaks off </li></ul><ul><li>Segment flips around backwards </li></ul><ul><li>Segment reattaches </li></ul>
  10. 10. Duplication <ul><li>Occurs when a gene sequence is repeated </li></ul>
  11. 11. Translocation <ul><li>Involves two chromosomes that aren’t homologous </li></ul><ul><li>Part of one chromosome is transferred to another chromosomes </li></ul>
  12. 12. Translocation
  13. 13. Nondisjunction <ul><li>Failure of chromosomes to separate during meiosis </li></ul><ul><li>Causes gamete to have too many or too few chromosomes </li></ul><ul><li>Disorders: </li></ul><ul><ul><li>Down Syndrome – three 21 st chromosomes </li></ul></ul><ul><ul><li>Turner Syndrome – single X chromosome </li></ul></ul><ul><ul><li>Klinefelter’s Syndrome – XXY chromosomes </li></ul></ul>
  14. 15. Chromosome Mutation Animation
  15. 17. Gene Mutations <ul><li>Change in the nucleotide sequence of a gene </li></ul><ul><li>May only involve a single nucleotide </li></ul><ul><li>May be due to copying errors , chemicals , </li></ul><ul><li>viruses , etc. </li></ul>
  16. 18. Types of Gene Mutations <ul><li>Include: </li></ul><ul><ul><li>Point Mutations </li></ul></ul><ul><ul><li>Substitutions </li></ul></ul><ul><ul><li>Insertions </li></ul></ul><ul><ul><li>Deletions </li></ul></ul><ul><ul><li>Frameshift </li></ul></ul>
  17. 19. Point Mutation <ul><li>Change of a single nucleotide </li></ul><ul><li>Includes the deletion, insertion, or substitution of ONE nucleotide in a gene </li></ul>
  18. 20. Point mutatioin may be transitions or transversioins
  19. 21. Effects <ul><li>Silent mutation </li></ul><ul><li>No detectable effect Especially if the changes is at the third position of the codon </li></ul><ul><li>eg. AAA - AAG </li></ul>2. Missense effect (mistaken amino acid) A. acceptable B. partially acceptable c. Unacceptable 3. Nonsense effect Premature termination of amino acid incoporation
  20. 23. Point Mutation <ul><li>Sickle Cell disease is the result of one nucleotide substitution </li></ul><ul><li>Occurs in the hemoglobin gene </li></ul>
  21. 24. Frameshift Mutation <ul><li>Inserting or deleting one or more nucleotides </li></ul><ul><li>Changes the “ reading frame ” like changing a sentence </li></ul><ul><li>Proteins built incorrectly </li></ul>
  22. 25. Amino Acid Sequence Changed
  23. 26. Gene Mutation Animation

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