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Mutations

Mutations. What Are Mutations?. Changes in the nucleotide sequence of DNA May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring. Are Mutations Helpful or Harmful?. Mutations happen regularly

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Mutations

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  1. Mutations

  2. What Are Mutations? • Changes in the nucleotide sequence of DNA • May occur in somatic cells (aren’t passed to offspring) • May occur in gametes (eggs & sperm) and be passed to offspring

  3. Are Mutations Helpful or Harmful? • Mutations happen regularly • Almost all mutations are neutral • Chemicals & UV radiation cause mutations • Many mutations are repaired by enzymes

  4. Are Mutations Helpful or Harmful? • Some type of skin cancers and leukemia result from somatic mutations • Some mutations may improve an organism’s survival (beneficial)

  5. Types of Mutations

  6. Chromosome Mutations • May Involve: • Changing the structure of a chromosome • The loss or gain of part of a chromosome

  7. Chromosome Mutations • Five types exist: • Deletion • Inversion • Translocation • Nondisjunction • Duplication

  8. Deletion • Due to breakage • A piece of a chromosome is lost

  9. Inversion • Chromosome segment breaks off • Segment flips around backwards • Segment reattaches

  10. Duplication • Occurs when a gene sequence is repeated

  11. Translocation • Involves two chromosomes that aren’t homologous • Part of one chromosome is transferred to another chromosomes

  12. Translocation

  13. Nondisjunction • Failure of chromosomes to separate during meiosis • Causes gamete to have too many or too few chromosomes • Disorders: • DownSyndrome – three 21st chromosomes • Turner Syndrome – single X chromosome • Klinefelter’s Syndrome – XXY chromosomes

  14. Chromosome Mutation Animation

  15. Gene Mutations • Change in the nucleotide sequence of a gene • May only involve a single nucleotide • May be due to copying errors, chemicals, viruses, etc.

  16. Types of Gene Mutations • Include: • Point Mutations • Substitutions • Insertions • Deletions • Frameshift

  17. Point Mutation • Change of a single nucleotide • Includes the deletion, insertion, or substitution of ONE nucleotide in a gene

  18. Point Mutation • Sickle Cell disease is the result of one nucleotide substitution • Occurs in the hemoglobin gene

  19. Frameshift Mutation • Inserting or deleting one or more nucleotides • Changes the “reading frame” like changing a sentence • Proteins built incorrectly

  20. Frameshift Mutation • Original: • The fat cat ate the wee rat. • Frame Shift (“a” added): • The fat caa tet hew eer at.

  21. Amino Acid Sequence Changed

  22. Gene Mutation Animation

  23. FYI

  24. Normal Male 2n = 46

  25. Normal Female 2n = 46

  26. Male, Trisomy 21 (Down’s) 2n = 47

  27. Female Down’s Syndrome 2n = 47

  28. Klinefelter’s Syndrome 2n = 47

  29. Turner’s Syndrome 2n = 45

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