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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 thenucleotide 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 • Mutations can be helpful, harmful, and neutral

  4. Types of Mutations

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

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

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

  8. Deletions When a chromosome fragment breaks off and does not rejoin any chromosome. Cri-du-chat (cry of the cat) Syndrome Cognitive impairment Improperly constructed larynx

  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 chromosomesthat aren’t homologous • Part of one chromosome is transferred to another chromosome

  12. Nondisjunction • Failure of chromosomes toseparate during meiosis • Causes gamete to have too manyortoo fewchromosomes • Disorders: • Down Syndrome–three 21st chromosomes • Turner Syndrome–single X chromosome • Klinefelter’s Syndrome–XXY chromosomes

  13. Down Syndrome 90% from egg nondisjunction 10% from sperm nondisjunction Smallish, oval heads IQ well below normal Reduced life span Risk increases with mothers over 35.

  14. Turner’s Syndrome Only one X chromosome Called XO Ovaries don’t develop properly Short in stature Brown spots on their bodies

  15. Klinefelter Syndrome Phenotypically male XXY Some breast development Lack of facial hair More feminine figure Tall stature Non-functional testis

  16. Chromosome Mutation Animation

  17. Gene Mutations • Change in the nucleotide sequenceof a gene • May only involve a single nucleotide • May be due to copyingerrors, chemicals, viruses, etc.

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

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

  20. Point Mutation • Sickle Cell disease is the result of one nucleotide substitution • Occurs in the hemoglobin gene • These cells clog capillaries, resulting in decreased oxygen supply to brain, tissues. • Lower life expectancy (42, men 48, women)

  21. Frameshift Mutation • Inserting or deletingone or more nucleotides • Changes the “reading frame” like changing a sentence • Proteinsbuilt incorrectly

  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

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