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Human Genetic Traits

Human Genetic Traits. Beliefs about Heredity. Fig. 1. De la propagation du genre humain, ou manuel indispensable pour ceux qui veulent avoir de beaux enfants de l’un ou l’autre sexe (Paris, Year VII). Image courtesy of the Bibliothèque Interuniversitaire de Médecine, Paris. Homunculus.

deirdre-davenport
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Human Genetic Traits

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  1. Human Genetic Traits

  2. Beliefs about Heredity Fig. 1. De la propagation du genre humain, ou manuel indispensable pour ceux qui veulent avoir de beaux enfants de l’un ou l’autre sexe (Paris, Year VII). Image courtesy of the Bibliothèque Interuniversitaire de Médecine, Paris.

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

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

  5. Darwin What he got right. What he got wrong. • Likes produce likes • Change can be permanent • There is no limit to cumulative change • Acquired characteristics Ex. Blind cave animals • Sex. Repro.- gemmules from all over body are packed in sperm and egg • Blended inheritance

  6. Mendelian Genetics Gregor Mendel

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

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

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

  10. 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

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

  12. Human Genome Project • U.S. govt. project coordinated by the Department of Energy and the National Institutes of Health, launched in 1986 by Charles DeLisi. • Definition: GENOME – the whole hereditary information of an organism that is encoded in the DNA. • Project Goal: to identify the approximate 100,000 genes in the human DNA. • determine the sequences of the 3 billion bases that make up human DNA. • store this information in databases. • develop tools for data analysis. • address the ethical, legal, and social issues that arise from genome research.

  13. Modeled Organisms • Bacteria (E. coli, influenza, several others) • Yeast (Saccharomyces cerevisiae) • Plant (Arabidopsis thaliana) • Fruit fly (Drosophila melanogaster) • Mouse (Mus musculus)

  14. Craig Venter Celera Genomics

  15. Importance of genetics • Understanding hereditary diseases and to develop new treatments • Donor matches • Paternity • Forensics • Evolution • Migration

  16. Polynesian Origins mtDNA Bismarck Archipelago 3.5ka http://www.sciencedaily.com/releases/2011/02/110203124726.htm

  17. Polynesian Origins

  18. Genetic Testing • Would you want to know? • Ethical concerns • Cost • Insurance companies

  19. Difference between Meiosis and Mitosis

  20. Meiosis I Interphase Prophase I Metaphase I Anaphase I Telephase I

  21. Crossing Over of Nonsister Chromatids between Homologous Chromosomes

  22. Meiosis II Prophase II Metaphase II Anaphase II Telephase II

  23. Genetic Testing

  24. Gel electrophoresis

  25. Polymerase Chain Reaction • PCR way of copying specific DNA fragments from small sample DNA material "molecular photocopying" • It’s fast, inexpensive and simple

  26. Genetic Testing $299, looks at specific diseases 23 and me Paternity Test $99

  27. Genetic Definitions • Genes- genetic material on a chromosome that codes for a specific trait • Genotype- the genetic makeup of the organism • Phenotype- the expressed trait • Allel- an alternative form of a gene

  28. 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

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

  30. Homologous Chromosomes gene: location allele: specific trait

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

  32. Allele Examples appearance eye color:homozygous

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

  34. Genotype vs Phenotype genotype phenotype homozygous(dominant) heterozygous homozygous (recessive) appearance

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

  36. 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

  37. 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

  38. Where Does Genetic Diversity Come From? • Mutation • Chromosomal Aberrations • Genetic Recombination (e.g., from sexual reproduction)

  39. Sickle Cell Mutation NORMAL Hb CTG ACT CCT GAG GAG AAG TCT Leu Thr Pro Glu Glu Lys Ser SICKLE CELL CTG ACT CCT GAG GTG AAG TCT Leu Thr Pro Glu Val Lys Ser mutation

  40. Autosomes and Sex Chromosomes

  41. 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

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

  43. 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

  44. Genotypes Phenotypes Experiment to determinedominant vs. recessive

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

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

  47. Complexities • Co-dominance-neither allele is recessive and the phenotypes of both alleles are expressed. • Blood types- AB (not O); sickle cell anemia heterochromia

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

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