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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 • Many mutations are repaired by enzymes

  4. Are Mutations Helpful or Harmful? • Some type of skin cancers and leukemia result from somatic mutations • Genetic disorders like sickle cell result from mutations that affect all cells

  5. Are mutations helpful or harmful? • Some mutations may improve an organism’s survival (beneficial)—the ultimate source of variation in the living world!

  6. Types of Mutations

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

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

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

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

  11. Duplication • Occurs when a gene sequence is repeated

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

  13. Translocation

  14. Nondisjunction • Failure of chromosomes to separate during meiosis • Causes gamete to have too many or too few chromosomes

  15. Chromosome Mutation Animation

  16. 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.

  17. Types of Gene Mutations • Include: • Substitutions • Insertions • Deletions

  18. Substitution • Change of a single nucleotide • Often called a “point mutation” because it happens at a single point

  19. Substitution • Sickle Cell disease is the result of one nucleotide substitution • Occurs in the hemoglobin gene

  20. Substitution • Substitutions can also be silent mutations—meaning they have no effect on the protein

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

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

  23. Amino Acid Sequence Changed

  24. Gene Mutation Animation

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