What’s a “mutagen”? What does a mutation do to DNA?

1. What’s a “mutagen”? • What does a mutation do to DNA? • If a mutation affects a gene, then what might happen to the protein sequence?

2. Genetic disorders • Some geneticdisorders are caused by mutations and errors in the DNA code

3. Types of mutations • Point mutation: a single base pair is substituted for another (ex. A  C)

4. Types of mutations • Insertion/deletion: results in a “frameshift”mutation (how codons are read, ordered, or sequenced)

6. Types of mutations • Large scale mutations: duplications/deletions of large chromosome sections; inversions that reverse gene sequences; translocations that exchange parts of nonhomologous chromosomes

8. Autosomal dominant disorders • In autosomal dominant disorders, you only need 1 copy of the allele to have the disease/trait

9. Huntington’s Disease • A neurodegenerative genetic disorder where nerve cells slowly break down

10. Huntington’s disease • Results in uncontrollable muscle movements and mental deterioration

11. Huntington’s disease • Caused by a defect on the 4th chromosome where the triplet CAG repeats more times than it should – the more triplets, the earlier the onset of the disease

12. Huntington’s disease • Symptoms normally don’t appear until age 30-50

13. Bioethics question of the day • If you found out that one of your parents has Huntington’s disease, would you choose to be tested for it yourself? (Yes or No)

14. Bioethics question of the day • If you found out that you, yourself, have Huntington’s disease, would you choose to have children? (Yes or No)

15. Autosomal recessive alleles • In autosomal recessive disorders, you need two copies of the allele in order to have the disease/trait

16. Cystic Fibrosis • Defective allele on chromosome 7 results in a faulty protein • Causes a thick, heavy mucus to build up and clog the lungs.

17. Cystic Fibrosis Need two recessive alleles - people with one normal chromosome produce enough of the correct protein

18. Cystic Fibrosis People with cystic fibrosis have problems breathing and digesting and are more vulnerable to lung infections

19. Cystic Fibrosis • Approximately 30,000 children and adults in the U.S. have cystic fibrosis. • About 1 in every 31 Americans are carriers of the defective CF gene, but do not have the disease. • CF is most common in Caucasians, but it can affect all races. (via the Cystic Fibrosis Foundation)

20. Sickle-cell Anemia • Red blood cells form a bent shape because of misshapen hemoglobin (carries oxygen in the blood)

21. Sickle-cell Anemia • People with sickle-cell suffer from painful episodes, fatigue, shortness of breath, and other health problems(hemoglobin carries oxygen in the blood).

22. Sickle-cell Anemia • One single base change to the normal allele results in sickled-cells.

23. Sickle-cell Anemia • One single base change to the normal allele results in sickled-cells.

24. Sickle-Cell and Malaria • Malaria is a mosquito-transmitted disease caused by a parasite that infects red blood cells, • More common in central parts of Africa, South America, and southern Asia.

25. Sickle-Cell and Malaria • People who are heterozygous for the trait (who have only one sickle-cell allele) are resistant to malaria but still have enough hemoglobin to function well.

26. Phenylketonuria (PKU) • A disease where the body cannot break down the amino acid phenylalanine

28. Phenylketonuria (PKU)

29. Phenylketonuria(PKU) • A missing enzyme causes phenylalanine to build up in the body; can eventually cause brain damage if the disease is not managed

30. Tay-sachs disease • Build of lipids in the central nervous system (CNS) – usually causes death by age 4

31. Tay-sachs disease • More common in specific populations

32. Examples of X-Linked Disorders • Colorblindness • Decreased ability to see or distinguish between certain colors • Red-green colorblindness, blue-yellow colorblindness

33. Examples of X-Linked Disorders • Decreased ability to see or distinguish between certain colors • Red-green colorblindness, blue-yellow colorblindness

34. Examples of X-Linked Disorders • Hemophilia • A bleeding disorder that prevents blood from clotting properly • The person bleeds more than someone without hemophilia

35. Examples of X-Linked Disorders • DuchenneMuscular Dystrophy • A disorder that involves rapidly increasing muscle weakness and loss of muscle tissue

36. Moving on…

37. Genetic disorders • Some genetic disorders are caused by chromosomal mutations

38. Genetic disorders • A karyotypeallows you to see all of the chromosomes in a single cell of an organism

39. Genetic disorders • With a karyotype, you can easily observe if there are any extra/missing chromosomes.

40. Karyotypes How many chromosomes do normal humans have? 46

41. Karyotypes How many are autosomal chromosomes? 44

42. Karyotypes How many are sex chromosomes (determine sex of the organism?) 2

43. Karyotypes • Looking at a karyotype, we can very easily observe if the organism has any extra or missing chromosomes that can result in certain genetic disorders.

44. Nondisjunction • “not coming apart” • The most common error in meiosis • Occurs when homologous chromosome pairs fail to separate during anaphase I or II, resulting in a sex cell with an extra or missing chromosome.

45. nondisjunction

46. Nondisjunction Disorders 1. Down Syndrome (Trisomy 21) • Three copies of chromosome 21

47. Nondisjunction Disorders 2. Turner’s Syndrome (X) • Only one copy of the X chromosome (no Y)

48. Nondisjunction Disorders 3. Klinefelter’s Syndrome(XXY) • Two copies of the X chromosome and a Y

49. Pedigrees • A diagram that shows the inheritance pattern of a trait over many generations is called a pedigree.

50. How To Read A Pedigree Pedigree Symbols MaleFemale I • Affected Carrier Person II Children/ Marriage Siblings III