1. Chapter 14 Mendel and the Gene Idea

2. Overview: Drawing from the Deck of Genes What genetic principles account for the passing of traits from parents to offspring? The “blending” hypothesis is the idea that genetic material from the two parents blends together (like blue and yellow paint blend to make green) Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

3. The “particulate” hypothesis is the idea that parents pass on discrete heritable units (genes) Mendel documented a particulate mechanism through his experiments with garden peas Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

4. 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.

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

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

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

8. Gregor Mendel Mendelian Genetics

9. Fig. 14-5-3 P Generation Appearance: Genetic makeup: Gametes: Purple flowers White flowers PP P pp p F 1 Generation Gametes: Genetic makeup: Appearance: Purple flowers Pp P p 1/21/2 1/21/2 F 2 Generation Sperm Eggs P P PPPp p p pp 31

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

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

12. 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

13. 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

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

15. 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

16. 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

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

18. Homologous Chromosomes gene: location allele: specific trait

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

20. Allele Examples appearance eye color: homozygous

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

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

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

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

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

26. Color blind- sex linked XSXs Y X Y XS Xs Y XS Y Xs S= color blind s= normal

27. Phenotype HbAHb_ HbAHbB X HbA HbB Hb_HbA Hb_ HbB HbA Hb_ HbB A B AB O Genotype Blood Type AA, A_ BB, B_ AB _ Outcome: AA, A_, AB, B_

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

29. Mutation  Mutations are changes to the sequence of nucleotide bases within a gene.  A possible consequence is the change in the amino acid sequence of a protein.  Mutations are rare, but occur often enough to be important (each of us will probably pass at least one mutation on to our offspring).

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

31. Mutation Some mutations may be deleterious, while others are may enhance chances for survival. Probably most mutations are neutral, having little or no effect on the fitness of the organism. Mutations may accumulate generation after generation, eventually leading to substantial differences in the characteristics of a species over time. Some mutations may be deleterious, while others are may enhance chances for survival. Probably most mutations are neutral, having little or no effect on the fitness of the organism. Mutations may accumulate generation after generation, eventually leading to substantial differences in the characteristics of a species over time.

32. Autosomes and Sex Chromosomes

33. Red-Green Color Blindness Sex-linked trait XCXC Y XCXC XcXc X XCXC XcXc YXCXC XCXC XCXC XCXC Y XcXc XCXC Y XcXc Normal male Normal female recessive gene Possible outcomes:X C X C X C X c X C YX c Y Normal female Normal Female (carrier) Normal male Color-blind male

34. Dominance Most traits show complete dominance Blending unexpected

35. Eunconnected earlobe econnected earlobe Eunconnected earlobe econnected earlobe allele gene PEE x ee gametes E e F1F1 unconnected connected

36. F1F1 Ee x Ee gametes 1/2 E 1/2 e E e Ee EEEe ee F2F2 1 EE 2 Ee 1 ee Punnett Square

37. P F1F1 F2F2 EE, ee Ee EE, 2 Ee, ee 50% 100% 75% 1:1 generation genotypes unconnected E:e Basis of the Castle-Hardy-Weinberg Law phenotypes ratio of alleles in the population

38. Genotypes Phenotypes Experiment to determine dominant vs. recessive

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

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

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

42. Degrees of Dominance Complete dominance occurs when phenotypes of the heterozygote and dominant homozygote are identical In incomplete dominance, the phenotype of F 1 hybrids is somewhere between the phenotypes of the two parental varieties In codominance, two dominant alleles affect the phenotype in separate, distinguishable ways Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

43. Fig. 14-10-1 Red P Generation Gametes White CRCRCRCR CWCWCWCW CRCR CWCW

44. Fig. 14-10-2 Red P Generation Gametes White CRCRCRCR CWCWCWCW CRCR CWCW F 1 Generation Pink CRCWCRCW CRCR CWCW Gametes 1/21/2 1/21/2

45. Fig. 14-10-3 Red P Generation Gametes White CRCRCRCR CWCWCWCW CRCR CWCW F 1 Generation Pink CRCWCRCW CRCR CWCW Gametes 1/21/2 1/21/2 F 2 Generation Sperm Eggs CRCR CRCR CWCW CWCW CRCRCRCR CRCWCRCW CRCWCRCW CWCWCWCW 1/21/2 1/21/2 1/21/2 1/21/2

46. Fig. 14-UN2 Degree of dominance Complete dominance of one allele Incomplete dominance of either allele Codominance Description Heterozygous phenotype same as that of homo- zygous dominant Heterozygous phenotype intermediate between the two homozygous phenotypes Heterozygotes: Both phenotypes expressed Multiple alleles Pleiotropy In the whole population, some genes have more than two alleles One gene is able to affect multiple phenotypic characters CRCRCRCR CRCWCRCW CWCWCWCW IAIBIAIB I A, I B, i ABO blood group alleles Sickle-cell disease PP Pp Example

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

48. Nature and Nurture: The Environmental Impact on Phenotype Another departure from Mendelian genetics arises when the phenotype for a character depends on environment as well as genotype The norm of reaction is the phenotypic range of a genotype influenced by the environment For example, hydrangea flowers of the same genotype range from blue-violet to pink, depending on soil acidity Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

49. Fig. 14-14

51. Tongue Roller R = Tongue Roller r = Unable to Roll Tongue

52. Widow’s Peak W = Widows Peak w = Lack of Widow’s Peak

53. Free Ear Lobe Attached Ear Lobe E = Free Ear Lobe e = Attached Ear Lobe

54. Hitchhiker’s Thumb Hi = Straight Thumb hi = Hitchhiker’s Thumb

55. Bent Little Finger Bf = Bent Little Finger bf = Straight Little Finger

56. Mid-digital Hair M = Mid-Digital Hair m = Absence of Mid-Digital Hair

57. Dimples D = Dimples d = Absence of Dimples

58. Short Hallux Ha = Short Hallux ha = Long Hallux

59. Short Index Finger S s = Short Index Finger S 1 = Long Index Finger *Sex-Influenced Trait

60. http://www.youtube.com/w atch?v=gCPuHzbb5hA

61. 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.

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

63. DNA from 5 humans: 2 males, 3 females 2 caucasians, one each of asian, african, hispanic Cut up DNA with restriction enzymes Ligated into BACs & YACs, then grew them up Sequenced the BACs Let a supercomputer put the pieces together

64. Craig Venter Celera Genomics

65. Importance of genetics Understanding hereditary diseases and to develop new treatmentsUnderstanding hereditary diseases and to develop new treatments Donor matchesDonor matches PaternityPaternity ForensicsForensics EvolutionEvolution MigrationMigration

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

67. Polynesian Origins

68. Genetic Testing Would you want to know? Ethical concerns Cost Insurance companies see

69. Genetic Testing

70. Gel electrophoresis

71. PCR is a rapid, inexpensive and simple way of copying specific DNA fragments from minute quantities of source DNA material Three steps are involved in PCR: Denaturation Annealing Extension Polymerase Chain Reaction

73. Genetic Testing Paternity Test $99 $99, looks at specific diseases

74. Counseling Based on Mendelian Genetics and Probability Rules Using family histories, genetic counselors help couples determine the odds that their children will have genetic disorders Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

75. Tests for Identifying Carriers For a growing number of diseases, tests are available that identify carriers and help define the odds more accurately Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

76. Fetal Testing In amniocentesis, the liquid that bathes the fetus is removed and tested In chorionic villus sampling (CVS), a sample of the placenta is removed and tested Other techniques, such as ultrasound and fetoscopy, allow fetal health to be assessed visually in utero Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Video: Ultrasound of Human Fetus I Video: Ultrasound of Human Fetus I

77. Fig. 14-18 Amniotic fluid withdrawn Fetus Placenta Uterus Cervix Centrifugation Fluid Fetal cells Several hours Several weeks Several weeks (a) Amniocentesis (b) Chorionic villus sampling (CVS) Several hours Several hours Fetal cells Bio- chemical tests Karyotyping Placenta Chorionic villi Fetus Suction tube inserted through cervix

78. n About 1-4% of DNA in Modern Europeans and Asians was inherited from Neanderthals Ozzy Osbourne's Genome Reveals Some Neanderthal Lineage http://www.scientificamerican.com/article.cfm?id=ozzy- osbourne-genome

79. You should now be able to: 1.Define the following terms: true breeding, hybridization, monohybrid cross, P generation, F 1 generation, F 2 generation 2.Distinguish between the following pairs of terms: dominant and recessive; heterozygous and homozygous; genotype and phenotype 3.Use a Punnett square to predict the results of a cross and to state the phenotypic and genotypic ratios of the F 2 generation Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

80. 4.Explain how phenotypic expression in the heterozygote differs with complete dominance, incomplete dominance, and codominance 5.Define and give examples of pleiotropy and epistasis 6.Explain why lethal dominant genes are much rarer than lethal recessive genes 7.Explain how carrier recognition, fetal testing, and newborn screening can be used in genetic screening and counseling Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings