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. Chromosomal Deletion One or more genes are removed Causes: Wolf-Hirschhorn syndrome (severe mental retardation) cri du chat syndrome (mewing sounds, mental retardation)

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

11. Chromosomal Inversion a segment of genes flip end-to-end on the chromosome Causes: Four-Ring Syndrome (cleft pallate, club feet, testes don’t descend)

12. Duplication  Occurs when a gene sequence is repeated

13. Chromosomal Duplication A segment of genes is copied twice and added to the chromosome Causes: Charcot–Marie–Tooth disease (high arched foot, claw feet, confined to a wheelchair)

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

15. Translocation

16. Chromosomal Translocation Material is swapped with another chromosome Causes: Burkitt’s Lymphoma (cancer of the lymph nodes, in children)

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

19. Nondisjunction  Chromosomes FAIL TO SEPARATE during meiosis  Meiosis I Nondisjunction Meiosis I Nondisjunction  Meiosis II Nondisjunction Meiosis II Nondisjunction

20. Nondisjunction  Produces gametes (and therefore a baby) with one missing chromosome or one extra chromosome

21. Nondisjunction (in Meiosis II)

22. Fertilization

23. Down Syndrome  Cause: Nondisjunction of chromosome 21  Three copies of chromosome 21 = “TRISOMY 21”

24. Trisomy 21 - Down Syndrome

25. Sex Chromosome Abnormalities  Klinefelter’s Syndrome  XXY, XXYY, XXXY  Male  Sterility  Small testicles  Breast enlargement

26. Sex Chromosome Abnormalities  XYY Syndrome  Normal male traits  Often tall and thin  Associated with antisocial and behavioral problems

27. Sex Chromosome Mutations  Turner’s Syndrome  X  Female  sex organs don't mature at adolescence  sterility  short stature

28. Sex Chromosome Mutations  XXX  Trisomy X  Female  Little or no visible differences  tall stature  learning disabilities  limited fertility

29. 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.

30. Types of Gene Mutations  Include:  Point Mutations  Substitutions  Insertions  Deletions  Frameshift

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

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

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

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

35. Amino Acid Sequence Changed