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  1. Table of Contents – pages iv-v Unit 1:What is Biology? Unit 2:Ecology Unit 3:The Life of a Cell Unit 4:Genetics Unit 5:Change Through Time Unit 6:Viruses, Bacteria, Protists, and Fungi Unit 7:Plants Unit 8:Invertebrates Unit 9:Vertebrates Unit 10:The Human Body

  2. Table of Contents – pages iv-v Unit 1: What is Biology? Chapter 1:Biology: The Study of Life Unit 2: Ecology Chapter 2:Principles of Ecology Chapter 3:Communities and Biomes Chapter 4:Population Biology Chapter 5:Biological Diversity and Conservation Unit 3:The Life of a Cell Chapter 6:The Chemistry of Life Chapter 7:A View of the Cell Chapter 8:Cellular Transport and the Cell Cycle Chapter 9:Energy in a Cell

  3. Unit 4: Genetics Chapter 10:Mendel and Meiosis Chapter 11:DNA and Genes Chapter 12:Patterns of Heredity and Human Genetics Chapter 13:Genetic Technology Unit 5: Change Through Time Chapter 14:The History of Life Chapter 15:The Theory of Evolution Chapter 16:Primate Evolution Chapter 17:Organizing Life’s Diversity Table of Contents – pages iv-v

  4. Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18:Viruses and Bacteria Chapter 19:Protists Chapter 20:Fungi Unit 7: Plants Chapter 21:What Is a Plant? Chapter 22:The Diversity of Plants Chapter 23:Plant Structure and Function Chapter 24:Reproduction in Plants Table of Contents – pages iv-v

  5. Table of Contents – pages iv-v Unit 8: Invertebrates Chapter 25:What Is an Animal? Chapter 26:Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27:Mollusks and Segmented Worms Chapter 28:Arthropods Chapter 29:Echinoderms and Invertebrate Chordates

  6. Table of Contents – pages iv-v Unit 9: Vertebrates Chapter 30:Fishes and Amphibians Chapter 31:Reptiles and Birds Chapter 32:Mammals Chapter 33:Animal Behavior Unit 10: The Human Body Chapter 34:Protection, Support, and Locomotion Chapter 35:The Digestive and Endocrine Systems Chapter 36:The Nervous System Chapter 37:Respiration, Circulation, and Excretion Chapter 38:Reproduction and Development Chapter 39:Immunity from Disease

  7. Unit Overview – pages 250-251 Genetics Mendel and Meiosis DNA and Genes Patterns of Heredity and Human Genetics Genetic Technology

  8. Chapter Contents – page viii Chapter 12Patterns of Heredity and Human Genetics 12.1:Mendelian Inheritance of Human Traits 12.1:Section Check 12.2:When Heredity Follows Different Rules 12.2:Section Check 12.3:Complex Inheritance of Human Traits 12.3:Section Check Chapter 12Summary Chapter 12Assessment

  9. Chapter Intro-page 308 What You’ll Learn You will compare the inheritance of recessive and dominant traits in humans. You will analyze the inheritance patterns of traits with incomplete dominance and codominance. You will determine the inheritance of sex-linked traits.

  10. 12.1 Section Objectives – page 309 Section Objectives: • Interpret a pedigree. • Identify human genetic disorders caused by inherited recessive alleles. • Predict how a human trait can be determined by a simple dominant allele.

  11. Section 12.1 Summary – pages 309 - 314 Making a Pedigree • A family tree traces a family name and various family members through successive generations. • Through a family tree, you can identify the relationships among your cousins, aunts, uncles, grandparents, and great-grandparents.

  12. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance • A pedigree is a graphic representation of genetic inheritance. • It is a diagram made up of a set of symbols that identify males and females, individuals affected by the trait being studied, and family relationships.

  13. Section 12.1 Summary – pages 309 - 314 Male Parents Siblings Female Pedigrees illustrate inheritance Affected male Known heterozygotes for recessive allele Affected female Death Mating

  14. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance Female Male I 1 2 II 2 1 4 5 3 • In a pedigree, a circle represents a female; a square represents a male. III 1 4 2 3 ? IV 5 3 4 2 1

  15. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance I 1 2 II 3 2 1 4 5 • Highlighted circles and squares represent individuals showing the trait being studied. III 1 4 2 3 ? IV 2 3 5 1 4

  16. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance I 1 2 II • Circles and squares that are not highlighted designate individuals that do not show the trait. 2 3 4 5 1 III 1 4 2 3 ? IV 3 5 2 4 1

  17. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance • A half-shaded circle or square represents a carrier, a heterozygous individual.

  18. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance • A horizontal line connecting a circle and a square indicates that the individuals are parents, and a vertical line connects parents with their offspring. I 1 2 II 4 2 3 1 5 III 1 4 2 3 ? IV 2 3 5 1 4

  19. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance • Each horizontal row of circles and squares in a pedigree designates a generation, with the most recent generation shown at the bottom. I 1 2 II 3 1 2 4 5 III 1 2 4 3 ? IV 3 5 1 2 4

  20. Section 12.1 Summary – pages 309 - 314 Pedigrees illustrate inheritance • The generations are identified in sequence by Roman numerals, and each individual is given an Arabic number. I 1 2 II 3 1 2 4 5 III 1 2 4 3 ? IV 3 5 1 2 4

  21. Section 12.1 Summary – pages 309 - 314 Simple Recessive Heredity • Most genetic disorders are caused by recessive alleles. Cystic fibrosis • Cystic fibrosis (CF) is a fairly common genetic disorder among white Americans.

  22. Section 12.1 Summary – pages 309 - 314 Cystic fibrosis • Approximately one in 28 white Americans carries the recessive allele, and one in 2500 children born to white Americans inherits the disorder. • Due to a defective protein in the plasma membrane, cystic fibrosis results in the formation and accumulation of thick mucus in the lungs and digestive tract.

  23. Section 12.1 Summary – pages 309 - 314 Tay-Sachs disease • Tay-Sachs (tay saks) disease is a recessive disorder of the central nervous system. • In this disorder, a recessive allele results in the absence of an enzyme that normally breaks down a lipid produced and stored in tissues of the central nervous system. • Because this lipid fails to break down properly, it accumulates in the cells.

  24. Section 12.1 Summary – pages 309 - 314 I 1 2 Typical Pedigree for II 1 2 4 3 Tay-Sachs III 3 1 2 IV 1

  25. Section 12.1 Summary – pages 309 - 314 Phenylketonuria • Phenylketonuria (fen ul kee tun YOO ree uh), also called (PKU), is a recessive disorder that results from the absence of an enzyme that converts one amino acid, phenylalanine, to a different amino acid, tyrosine. • Because phenylalanine cannot be broken down, it and its by-products accumulate in the body and result in severe damage to the central nervous system.

  26. Section 12.1 Summary – pages 309 - 314 Phenylketonuria • A PKU test is normally performed on all infants a few days after birth. • Infants affected by PKU are given a diet that is low in phenylalanine until their brains are fully developed. • Ironically, the success of treating phenylketonuria infants has resulted in a new problem.

  27. Section 12.1 Summary – pages 309 - 314 Phenylketonuria • If a female who is homozygous recessive for PKU becomes pregnant, the high phenylalanine levels in her blood can damage her fetus—the developing baby. • This problem occurs even if the fetus is heterozygous and would be phenotypically normal.

  28. Section 12.1 Summary – pages 309 - 314 Phenylketonuria Phenylketonurics: Contains Phenylalanine

  29. Section 12.1 Summary – pages 309 - 314 Simple Dominant Heredity • Many traits are inherited just as the rule of dominance predicts. • Remember that in Mendelian inheritance, a single dominant allele inherited from one parent is all that is needed for a person to show the dominant trait.

  30. Section 12.1 Summary – pages 309 - 314 Simple dominant traits • A cleft chin, widow’s peak hairline, hitchhiker’s thumb, almond shaped eyes, thick lips, and the presence of hair on the middle section of your fingers all are examples of dominant traits.

  31. Section 12.1 Summary – pages 309 - 314 Huntington’s disease • Huntington’s disease is a lethal genetic disorder caused by a rare dominant allele. • It results in a breakdown of certain areas of the brain.

  32. Section 12.1 Summary – pages 309 - 314 Huntington’s disease • Ordinarily, a dominant allele with such severe effects would result in death before the affected individual could have children and pass the allele on to the next generation. • But because the onset of Huntington’s disease usually occurs between the ages of 30 and 50, an individual may already have had children before knowing whether he or she is affected.

  33. Section 12.1 Summary – pages 309 - 314 Typical Pedigree of Huntington’s Disease I 1 2 II 2 5 1 4 3 III 1 2 3 4 5

  34. Section 1 Check Question 1 I 1 2 What does this pedigree tell you about those who show the recessive phenotype for the disease? II 1 2 4 3 III 3 1 2 IV 1

  35. Section 1 Check I The pedigree indicates that showing the recessive phenotype for the disease is fatal. 1 2 II 1 2 4 3 III 3 1 2 IV 1

  36. Section 1 Check Question 2 What must happen for a person to show a recessive phenotype? Answer The person must inherit a recessive allele for the trait from both parents.

  37. Section 1 Check Question 3 Which of the following diseases is the result of a dominant allele? A. Huntington’s disease B. Tay-Sachs disease C. cystic fibrosis D. phenylketonuria The answer is A.

  38. 12.2 Section Objectives – page 315 Section Objectives: • Distinguish between alleles for incomplete dominance and codominance. • Explain the patterns of multiple allelic and polygenic inheritance. • Analyze the pattern of sex-linked inheritance. • Summarize how internal and external environments affect gene expression.

  39. Section 12.2 Summary – pages 315 - 322 Complex Patterns of Inheritance • Patterns of inheritance that are explained by Mendel’s experiments are often referred to as simple. • However, many inheritance patterns are more complex than those studied by Mendel.

  40. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype • When inheritance follows a pattern of dominance, heterozygous and homozygous dominant individuals both have the same phenotype. • When traits are inherited in an incomplete dominance pattern, however, the phenotype of heterozygous individuals is intermediate between those of the two homozygotes.

  41. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype • For example, if a homozygous red-flowered snapdragon plant (RR) is crossed with a homozygous white-flowered snapdragon plant (R′ R′), all of the F1 offspring will have pink flowers.

  42. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype White Red All pink Red (RR) Pink (RR’) White (R’R’) Pink (RR’) All pink flowers 1 red: 2 pink: 1 white

  43. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype • The new phenotype occurs because the flowers contain enzymes that control pigment production. • The R allele codes for an enzyme that produces a red pigment. The R’ allele codes for a defective enzyme that makes no pigment.

  44. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype • Because the heterozygote has only one copy of the R allele, its flowers appear pink because they produce only half the amount of red pigment that red homozygote flowers produce.

  45. Section 12.2 Summary – pages 315 - 322 Incomplete dominance: Appearance of a third phenotype White Red All pink Red (RR) Pink (RR’) White (R’R’) Pink (RR’) All pink flowers 1 red: 2 pink: 1 white

  46. Section 12.2 Summary – pages 315 - 322 Codominance: Expression of both alleles • Codominant alleles cause the phenotypes of both homozygotes to be produced in heterozygous individuals. In codominance, both alleles are expressed equally.

  47. Section 12.2 Summary – pages 315 - 322 Multiple phenotypes from multiple alleles • Although each trait has only two alleles in the patterns of heredity you have studied thus far, it is common for more than two alleles to control a trait in a population. • Traits controlled by more than two alleles have multiple alleles.

  48. Section 12.2 Summary – pages 315 - 322 Sex determination • In humans the diploid number of chromosomes is 46, or 23 pairs. • There are 22 pairs of homologous chromosomes called autosomes. Homologous autosomes look alike. • The 23rd pair of chromosomes differs in males and females.

  49. Section 12.2 Summary – pages 315 - 322 Sex determination • These two chromosomes, which determine the sex of an individual, are called sex chromosomes and are indicated by the letters X and Y.