1. Patterns of Inheritance Chapter 9 Part 2

2. 9.4 Complex Variations in Traits  A trait that is influenced by the products of multiple genes often occurs in a range of small increments of phenotype (continuous variation)  The more genes and other factors that influence a trait, the more continuous the distribution of phenotype

3. Continuous Variation  Continuous variation A range of small differences in a shared trait  Bell curve Curve that typically results when range of variation in a continuous trait is plotted against frequency in a population

4. Continuous Variation (Bell Curve)

5. Fig. 9-12a, p. 165

6. Fig. 9-12b, p. 165

7. Animation: Continuous variation in height

8. Environmental Effects on Phenotype  Enzymes and other gene products control steps of most metabolic pathways  Mutations, interactions among genes, and environmental conditions can affect one or more steps, and contribute to variation in phenotypes

9. Environmental Effects on Animal Phenotypes  Snowshoe hare in summer and winter  Daphnia without and with predators

10. Fig. 9-13a, p. 166

11. Fig. 9-13b, p. 166

12. Fig. 9-13c, p. 166

13. Environmental Effects on Plant Phenotypes

14. Fig. 9-14, p. 166 60 Height (centimeters) 000 A Plant grown at high elevation (3,060 meters above sea level) B Plant grown at mid-elevation (1,400 meters above sea level) C Plant grown at low elevation (30 meters above sea level)

15. Animation: Coat color in the Himalayan rabbit

16. 9.5 Human Genetic Analysis  Inheritance patterns in humans are studied by following inherited genetic disorders through generations and graphing results as pedigrees  Pedigree Chart showing the pattern of inheritance of a gene in a family

17. Pedigree: Polydactyly

18. Fig. 9-15, p. 167 marriage/mating female male offspring individual showing trait being studied sex not specified generation A Standard symbols used in pedigrees *Gene not expressed in this carrier. B A pedigree for polydactyly, which is characterized by extra fingers, toes, or both. The black numbers signify the number of fingers on each hand; the blue numbers signify the number of toes on each foot.

19. marriage/mating female male offspring individual showing trait being studied sex not specified generation A) Standard symbols used in pedigrees B) A pedigree for polydactyly, which is characterized by extra fingers, toes, or both. The black numbers signify the number of fingers on each hand; the blue numbers signify the number of toes on each foot. Fig. 9-15, p. 167 *Gene not expressed in this carrier. Stepped Art

20. Animation: Pedigree diagrams

21. Genetic Abnormalities and Disorders  Genetic abnormality An uncommon version of a heritable trait that does not result in medical problems  Genetic disorder A heritable condition that results in a syndrome of mild or severe medical problems  Syndrome Set of symptoms characterizing a genetic disorder

22. 9.6 Human Genetic Disorders  Some dominant or recessive alleles on autosomes or the X chromosome are associated with genetic abnormalities or disorders  An autosomal dominant allele is expressed in homozygotes and heterozygotes  An autosomal recessive allele is expressed only in homozygotes

23. Some Autosomal Dominant Disorders

24. Autosomal Dominant Inheritance

25. Fig. 9-16a, p. 168 normal mother affected father meiosis and gamete formation affected child normal child disorder-causing allele (dominant)

26. Fig. 9-16b, p. 168

27. Animation: Autosomal-dominant inheritance

28. Some Autosomal Recessive Disorders

29. Autosomal Recessive Inheritance

30. Fig. 9-17a, p. 169 carrier mothercarrier father meiosis and gamete formation affected child carrier child normal child disorder-causing allele (recessive)

31. Animation: Autosomal-recessive inheritance

32. X-Linked Recessive Disorders  Alleles on the X chromosome are inherited and expressed differently in males and females  Males cannot transmit a recessive X-linked allele to their sons  Females pass X-linked alleles to male offspring Example: Queen Victoria of England and hemophilia

33. Some X-Linked Recessive Disorders

34. X-Linked Recessive Inheritance

35. Fig. 9-18 (top), p. 170

36. Fig. 9-18 (a-d), p. 170

37. Animation: X-linked inheritance

38. An X-Linked Trait: Queen Victoria and Hemophilia

39. Animation: Morgan’s reciprocal crosses

40. Video: ABC News: Genetic testing: Screening embryos for disease

41. 9.7 Changes in Chromosome Number  Chromosome number can change permanently, usually resulting from nondisjunction  Nondisjunction Failure of duplicated chromosomes (sister chromatids) or homologous chromosomes to separate during meiosis or mitosis

42. Nondisjunction During Meiosis

43. Fig. 9-20a, p. 172 Metaphase IAnaphase ITelophase IMetaphase IIAnaphase IITelophase II

44. Fig. 9-20b, p. 172 Stepped Art Metaphase I Anaphase I Telophase I Metaphase II Anaphase II Telophase II

45. Aneuploidy  Aneuploidy A chromosome abnormality in which a cell has too many or too few copies of a particular chromosome (trisomy, monosomy)  The most common aneuploidy in humans, trisomy 21, causes Down syndrome

46. Some Disorders Caused by Aneuploidy

47. Polyploidy  Autosomal aneuploidy is usually fatal in humans, but many flowering plants, and some insects, fishes and other animals are polyploid  Polyploid Having three or more of each type of chromosome characteristic of the species

48. Autosomal Change and Down Syndrome  Trisomy 21 (Down syndrome) The only autosomal trisomy that allows humans to survive to adulthood Affected individuals tend to have certain physical features and impairments  Nondisjunction leading to trisomy 21 increases with age of the mother

49. Autosomal Change and Down Syndrome

50. Fig. 9-20b, p. 172

51. Fig. 9-20c, p. 172

52. Sex Chromosome Abnormalities  Usually associated with learning difficulties, speech delays, and motor skill impairment  Female sex chromosome abnormalities: Turner syndrome (XO), XXX syndrome  Male sex chromosome abnormalities: Klinefelter syndrome (XXY); XYY syndrome

53. Turner’s Syndrome (XO)  Affects development of ovaries, sexual maturity

54. Animation: Nondisjunction

55. 9.8 Some Prospects in Human Genetics  Geneticists estimate the chance that a couple’s offspring will inherit a genetic abnormality or disorder  Potential parents who may be at risk of transmitting a harmful allele to offspring have screening or treatment options

56. Prenatal Diagnosis  Tests performed before birth Amniocentesis Chorionic villi sampling (CVS) Fetoscopy  Carry risks of miscarriage or injury to fetus

57. Amniocentesis  Risks of puncture, infection, loss of amniotic fluid

58. Animation: Amniocentesis

59. Fetoscopy  Increased risk of miscarriage

60. Preimplantation Diagnosis  A single cell taken from an embryo produced by in vitro fertilization is tested before implantation

61. Genetic Screening and Phenotypic Treatments  Genetic screening Hospitals routinely screen newborns for certain genetic disorders such as PKU (Phenylketonuria)  Phenotypic treatments Surgery, prescription drugs, hormone replacement therapy, or dietary controls can minimize symptoms of some genetic disorders

62. 9.9 Impacts/Issues Revisited  The cystic fibrosis (CF) allele is very common in some populations  The CF allele is lethal in homozygotes, but offers heterozygotes some protection against bacterial diseases such as typhoid fever

63. Digging Into Data: Cystic Fibrosis and Typhoid Fever