1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-1 Human Genetics Concepts and Applications Seventh Edition Powerpoint Lecture Outline Ricki Lewis Prepared by Mary King Kananen Penn State Altoona

2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-2 Chapter 4 Mendelian Inheritance

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-3 Inheritance A child inherits half of its genes from each parent How are traits assorted with each generation? Figure 4.1

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-4 Gregor Mendel Research in plant breeding Without knowledge of DNA, cells, or chromosomes Described the units of inheritance and how they pass from generation to generation Not recognized during his lifetime

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-5 Gregor Mendel Experimented from 1857-1863 Developed the laws of inheritance Used Controlled plant breeding Careful recordkeeping Large numbers Statistics

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-6 Mendel Studied Transmission of Seven Traits in the Pea Plants Figure 4.2

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-7 True Breeding Plants Offspring have the same trait as parent Examples: Round seeded parents –produce all round seeded offspring Yellow seeded parents –produce all yellow seeded offspring Short parents –produce all short offspring

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-8 Monohybrid Cross True breeding plants with two forms of a trait are crossed Progeny show only one form of the trait The observed trait is dominant The masked trait is recessive

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-9 Monohybrid Cross Parental generation (P 1 ) Tall X Short F1F1 All Tall F2F2 ¼ Short ¾ Tall Figure 4.3

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-10 Alleles Mendel’s units (or “elementen”) are alleles Versions of the same gene or DNA sequence. Differ in DNA sequence at one or more sites.

11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-11 Mendel's Law of Segregation Each plant possesses two units (alleles) for each trait Alleles separate in the formation of gametes Gametes contain ONE allele for each trait

12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-12 Figure 4.4

13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-13 Mendel’s Data Table 4.1

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-14 Genotype The alleles present in an individual –Homozygous carry the same alleles TT or tt –Heterozygous carry different alleles Tt Phenotype Indicates the trait observed Tall or Short Wild Type Most common phenotype Mutant phenotype A product of a change in the DNA Terms

15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-15 Punnett Square Represent particular genes in gametes and how they may combine Figure 4.5

16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-16 Test Cross Identifies parents with an unknown genotype Figure 4.6

17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-17 Autosomal Inheritance Human autosomal traits are located on the non sex chromosomes (1-22) They may be inherited as –Autosomal dominant or –Autosomal recessive

18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-18 Autosomal Dominant Homozygous dominant and heterozygotes exhibit the affected phenotype Males and females are equally affected and may transmit the trait Affected phenotype does not skip generation Figure 4.7

19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-19 Autosomal Recessive Only homozygous recessive individuals exhibit the affected phenotype Males and females are equally affected and may transmit the trait May skip generations Figure 4.8

20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-20 Box Figure 4.1

21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-21 Examples of Mendelian Disorders in Humans See Table 4.2 in text, p. 80 Thousands of examples are described in the database Online Mendelian Inheritance in Man www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM

22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-22 Probability The likelihood that an event will occur The probability that a coin will land heads up is ½ The probability that a heterozygous individual (Bb) will produce a gamete with the B allele is ½

23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-23 Solving Genetics Problems List genotypes and phenotypes for the trait Determine the genotypes of the parents Possible gametes Possible genotypes of offspring Repeat for successive generations

24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-24 Genetics Problems Examples

25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-25 Meaning of Dominance and Recessive Whether an allele is dominant or recessive is important in determining risk and critical in medical genetics Reflect the characteristics or abundance of a protein Recessive traits have “loss of function” Dominant traits have “gain of function”

26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-26 Maintaining Detrimental or Lethal Alleles in a Population Recessive traits are maintained in a population in the heterozygotes How can a dominant lethal allele such as Huntington disease be maintained in a population?

27. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-27 Mendel’s Second Law of Independent Assortment Two genes on different chromosomes segregate their alleles independently The inheritance of one does not influence the chance of inheriting the other

28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-28 Law of Independent Assortment Figure 4.9

29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-29 Independent Assortment of Two Traits Figure 4.10

30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-30 Independent Events The probability of simultaneous independent events = the product of the probability of each event Example: If both parents are heterozygous (Bb)) what is the probability that they will produce a BB child? Probability of a sperm with B allele = ½ Probability of a ova with B allele = ½ Probability of a BB child is ½ X ½ = ¼

31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-31 Independent Events If both parents are heterozygous for two genes, what is the probability of having a homozygous recessive child? Figure 4.11

32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-32 Figure 4.12

33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-33 Dependent Events The probability of dependent events = the sum of probability of each event Example Parents are heterozygous for a trait, R. What is the chance that their child carries at least one dominant R allele? Probability of child carrying RR = ¼ Probability of child carrying Rr = ½ Probability of child carrying R_ = ¼ + ½ = ¾

34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-34 Pedigrees symbolic representations of family relationships and inheritance of a trait Figure 4.13

35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-35 A Pedigree with Consanguinity Figure 4.14a

36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-36 Autosomal Recessive Inheritance Albinism Figure 4.15

37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-37 Autosomal Dominant Inheritance Brachydactyly Figure 4.16

38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-38 Inconclusive Figure 4.17

39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-39 Genetic Predictions Ellen’s brother Michael has sickle cell anemia, an autosomal recessive disease. What is the probability that Ellen’s child has a sickle cell anemia allele?

40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-40 Ellen and Michael’s parents must be heterozygous S s SsSs SSSs ss Ellen is not affected and cannot be aa Probability Ellen is a carrier = 2/3 Probability child inherits sickle cell allele = ½ Probability child carries sickle cell allele from Ellen = 2/3 x 1/2 = 1/3 Figure 4.18a

41. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-41 Applied Questions Pedigrees Applied section pedigrees or other examples could be added here for instructors to use in classroom activities It may make the presentation excessively long. Perhaps, just make it a separate file.

42. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-42 Achondroplasia Text Figure 4.1

43. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-43 Chands Syndrome Text Figure 4.20

44. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-44 Congenital Insensitivity to Pain Text Figure 4.3

45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-45 Tay-Sachs Disease Text Figure 4.4

46. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-46 Sclerosteosis Figure 4.5

47. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-47 Freckles Text Figure 4.6