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Lecture 29c

Inheritance. Lecture 29c. Genetic Testing. Predisposition to disease Alzheimer's case (Feb. 2002) Amniocentesis & Chorionic villa Family history >35 years old Donor match Paternity Forensics. Genetic Testing. Would you want to know? Ethical concerns Cost Insurance companies

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Lecture 29c

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  1. Inheritance Lecture 29c

  2. Genetic Testing • Predisposition to disease • Alzheimer's case (Feb. 2002) • Amniocentesis & Chorionic villa • Family history • >35 years old • Donor match • Paternity • Forensics

  3. Genetic Testing • Would you want to know? • Ethical concerns • Cost • Insurance companies • see GATTACA

  4. Homunculus How is “heredity passed on: Spermist vs Ovists Spermist conception of a human sperm

  5. Homunculus Leeuwenhoek’s black male and white female rabbit experiments: spermist “proof”

  6. Mendel’s Three Principles • Dominance • Segregation • Independent Assortment (1822-1884) The foundation of “classical” science

  7. Dominance • Traits of both parents inherited, but one shows over the other • Traits are not blended

  8. Dominance Mechanism • Two alleles are carried for each trait • In true-breeding individuals, both alleles are the same (homozygous). • Hybrids, on the other hand, have one of each kind of allele (heterozygous). • One trait is dominant, the other trait is recessive

  9. Segregation • Half the gametes (egg or sperm) will carry the traits of one parent and half the traits for the other parent Pairs of alleles are separated (=segregated) during meiosis

  10. Independent Assortment Two different parental characteristics will be inherited independently of one another during gamete formation. Example: flower color and leaf shape

  11. Genetic Information • Genes are traits • “Eye color” • Ear lobe connectedness • Genes produce proteins • Enzymes are proteins

  12. Homologous Chromosomes gene: location allele: specific trait

  13. Allele Example • Gene = “eye color” • Alleles • brown • blue • green • lavender

  14. Allele Examples appearance eye color:homozygous

  15. Allele Examples appearance eye color:heterozygous, brown dominant over blue

  16. Genotype vs Phenotype genotype phenotype homozygous(dominant) heterozygous homozygous (recessive) appearance Phaner = visible

  17. Punnett Square If male & female are heterozygous for eye color male female X brown: 3/4 offspring blue: 1/4 offspring

  18. PKU Each parent carries one gene for PKU. P p P P P P p P p X P p P p p p p Possible genotypes: 1PP 2Pp 1pp Possible phenotypes:no PKU PKU

  19. Compare this to what would have happened if one parent was homozygous for sickle cell. HbA HbA HbA HbA HbS HbA HbA HbS HbS X HbA HbA HbS HbS HbS HbS HbS all offspring are carriers of sickle cell trait

  20. Autosomes and Sex Chromosomes

  21. Red-Green Color Blindness Sex-linked trait XC Y XC Y XC XC XC Normal male XC Y X XC Xc XC Xc Xc Xc Y Normal female recessive gene Possible outcomes: XCXC XCXc XCY XcY Normal female Normal Female (carrier) Normal male Color-blind male

  22. Dominance Most traits show complete dominance Blending unexpected

  23. allele gene E unconnected earlobe e connected earlobe unconnected P EE x ee connected E e gametes F1 Ee

  24. F1 Ee x Ee 1/2 E 1/2 e1/2 E 1/2 e gametes E e E EE Ee PunnettSquare e Ee ee F2 1 EE 2 Ee 1 ee

  25. generation genotypes unconnected E:e P EE, ee 50% 1:1 F1 Ee 100% 1:1 F2 EE, 2 Ee, ee 75% 1:1 phenotypes ratio of alleles in the population Basis of the Castle-Hardy-Weinberg Law

  26. Genotypes Phenotypes Experiment to determinedominant vs. recessive

  27. Genetic Sleuthing My eye color phenotype is brown. What is my genotype?

  28. Pedigree phenotypes infer genotypes Alternative: look directly at the DNA

  29. Complexities • Multiple genes for one trait • Example: eye color • Blended traits (“incomplete dominance”) • Influence of the environment

  30. Disorders Down’s Syndrome (chrom 21) Alzheimer’s (chrom 1, 10, 14, 19, 21) Huntington’s (chrom 4)

  31. Human Genetic Traits

  32. Tongue Roller R = Tongue Rollerr = Unable to Roll Tongue

  33. Widow’s Peak W = Widows Peakw = Lack of Widow’s Peak

  34. Attached Ear Lobe Free Ear Lobe E = Free Ear Lobee = Attached Ear Lobe

  35. Hitchhiker’s Thumb Hi = Straight Thumbhi = Hitchhiker’s Thumb

  36. Bent Little Finger Bf = Bent Little Fingerbf = Straight Little Finger

  37. Mid-digital Hair M = Mid-Digital Hairm = Absence of Mid-Digital Hair

  38. Dimples D= Dimplesd = Absence of Dimples

  39. Short Hallux Ha = Short Halluxha = Long Hallux

  40. Short Index Finger Ss = Short Index FingerS1 = Long Index Finger *Sex-Influenced Trait

  41. Kiss me, you fool. Pttttthhhhhhhtttt! Presentation created by J. Kenyon

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