1. © 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 9 Patterns of Inheritance

2. © 2010 Pearson Education, Inc. Genetics is the scientific study of heredity. –Genetics explains why the offspring of purebred dogs are like their parents. –Inbreeding of dogs makes some genetic disorders common. A dog’s behavior is determined by its –Genes –Environment Biology And Society: A Matter of Breeding

3. Figure 9.00

4. © 2010 Pearson Education, Inc. Heredity is the transmission of traits from one generation to the next. Gregor Mendel –Worked in the 1860s –Was the first person to analyze patterns of inheritance –Deduced the fundamental principles of genetics HERITABLE VARIATION AND PATTERNS OF INHERITANCE

5. Figure 9.1

6. © 2010 Pearson Education, Inc. In an Abbey Garden Mendel studied garden peas because they –Are easy to grow –Come in many readily distinguishable varieties –Are easily manipulated –Can self-fertilize

7. Carpel (produces eggs) Stamen (makes sperm- producing pollen) Petal Figure 9.2

8. © 2010 Pearson Education, Inc. A character is a heritable feature that varies among individuals. A trait is a variant of a character. Each of the characters Mendel studied occurred in two distinct forms.

9. © 2010 Pearson Education, Inc. Mendel –Created true-breeding varieties of plants –Crossed two different true-breeding varieties Hybrids are the offspring of two different true-breeding varieties. –The parental plants are the P generation. –Their hybrid offspring are the F 1 generation. –A cross of the F 1 plants forms the F 2 generation.

10. Removed stamens from purple flower. White Stamens Purple Transferred pollen from stamens of white flower to carpel of purple flower. Parents (P) Carpel Figure 9.3-1

11. Removed stamens from purple flower. White Stamens Purple Transferred pollen from stamens of white flower to carpel of purple flower. Parents (P) Carpel Pollinated carpel matured into pod. Figure 9.3-2

12. Removed stamens from purple flower. White Stamens Purple Transferred pollen from stamens of white flower to carpel of purple flower. Parents (P) Carpel Offspring (F 1 ) Pollinated carpel matured into pod. Planted seeds from pod. Figure 9.3-3

13. © 2010 Pearson Education, Inc. Mendel’s Law of Segregation Mendel performed many experiments. He tracked the inheritance of characters that occur as two alternative traits.

14. White Purple Recessive Dominant Green Yellow Terminal Axial Wrinkled Round Green Yellow Seed shape Seed color Flower position Flower color Pod color Recessive Dominant Pod shape Stem length Inflated Constricted Tall Dwarf Figure 9.4

16. © 2010 Pearson Education, Inc. Monohybrid Crosses A monohybrid cross is a cross between parent plants that differ in only one character. Blast Animation: Single-Trait Crosses

17. Purple flowers White flowers P Generation (true-breading parents) Figure 9.5-1

18. Purple flowers F 1 Generation White flowers P Generation (true-breading parents) All plants have purple flowers Figure 9.5-2

19. Purple flowers F 1 Generation White flowers P Generation (true-breading parents) All plants have purple flowers F 2 Generation Fertilization among F 1 plants (F 1  F 1 ) of plants have purple flowers of plants have white flowers 3 4 1 4 Figure 9.5-3

20. Figure 9.5

21. © 2010 Pearson Education, Inc. Mendel developed four hypotheses from the monohybrid cross: 1. There are alternative versions of genes, called alleles. 2. For each character, an organism inherits two alleles, one from each parent. –An organism is homozygous for that gene if both alleles are identical. –An organism is heterozygous for that gene if the alleles are different.

22. © 2010 Pearson Education, Inc. 3. If two alleles of an inherited pair differ –The allele that determines the organism’s appearance is the dominant allele –The other allele, which has no noticeable effect on the appearance, is the recessive allele

23. © 2010 Pearson Education, Inc. 4. Gametes carry only one allele for each inherited character. –The two members of an allele pair segregate (separate) from each other during the production of gametes. –This statement is the law of segregation.

24. © 2010 Pearson Education, Inc. Do Mendel’s hypotheses account for the 3:1 ratio he observed in the F 2 generation? A Punnett square highlights the four possible combinations of gametes and offspring that result from each cross. Blast Animation: Genetic Variation: Fusion of Gametes

25. Purple flowers White flowers P Generation Genetic makeup (alleles) Gametes Alleles carried by parents PP P pp p All Figure 9.6-1

26. Purple flowers F 1 Generation (hybrids) White flowers P Generation Genetic makeup (alleles) Gametes Alleles carried by parents PP P pp p All All Pp Purple flowers Gametes Alleles segregate P p 1 2 1 2 Figure 9.6-2

27. Purple flowers F 1 Generation (hybrids) White flowers P Generation Genetic makeup (alleles) Gametes Alleles carried by parents PP P pp p All All Pp Purple flowers Gametes Alleles segregate P p F 2 Generation (hybrids) Sperm from F 1 plant P p P p PP pp Pp Eggs from F 1 plant Phenotypic ratio 3 purple : 1 white Genotypic ratio 1 PP : 2 Pp : 1 pp 1 2 1 2 Figure 9.6-3

28. © 2010 Pearson Education, Inc. Geneticists distinguish between an organism’s physical traits and its genetic makeup. –An organism’s physical traits are its phenotype. –An organism’s genetic makeup is its genotype.

29. © 2010 Pearson Education, Inc. Genetic Alleles and Homologous Chromosomes Homologous chromosomes have –Genes at specific loci –Alleles of a gene at the same locus

30. Homologous chromosomes P Genotype: Gene loci P a aa b B Dominant allele Recessive allele Bb PP Homozygous for the dominant allele Homozygous for the recessive allele Heterozygous a Figure 9.7

31. © 2010 Pearson Education, Inc. Mendel’s Law of Independent Assortment A dihybrid cross is the crossing of parental varieties differing in two characters. What would result from a dihybrid cross? Two hypotheses are possible: 1. Dependent assortment 2. Independent assortment Blast Animation: Two-Trait Crosses

32. F 1 Generation F 2 Generation RRYY Predicted results (not actually seen) P Generation Gametes RY rryy ry (a) Hypothesis: Dependent assortment RrYy RY ry Sperm Eggs RY ry Actual results (support hypothesis) RRYY RY rryy ry RrYy (b) Hypothesis: Independent assortment Gametes RY ry Sperm RY ry Ry rY Ry rY RRYY Rryy RRyy RrYy RRYy RrYy rrYy Rryy rryy RrYY rrYY RrYyrrYy RRYy RrYy Yellow round Yellow wrinkled Green wrinkled Green round 1 2 1 2 1 2 1 2 1 4 1 4 1 4 1 4 1 4 1 4 1 4 1 4 1 16 3 3 9 Figure 9.8

34. © 2010 Pearson Education, Inc. Mendel’s dihybrid cross supported the hypothesis that each pair of alleles segregates independently of the other pairs during gamete formation. Thus, the inheritance of one character has no effect on the inheritance of another. This is the law of independent assortment. Independent assortment is also seen in two hereditary characters in Labrador retrievers.

35. Blind dog Phenotypes (a) Possible phenotypes of Labrador retrievers B_N_ Blind dog Genotypes (b) A Labrador dihybrid cross Black coat, normal vision B_nn Black coat, blind (PRA) bbnn Chocolate coat, blind (PRA) bbN_ Chocolate coat, normal vision Mating of double heterozygotes (black coat, normal vision) BbNn Phenotypic ratio of offspring 9 black coat, normal vision 3 black coat, blind (PRA) 3 chocolate coat, normal vision 1 chocolate coat, blind (PRA) Figure 9.9

36. Blind dog Phenotypes (a) Possible phenotypes of Labrador retrievers B_N_ Blind dog Genotypes Black coat, normal vision B_nn Black coat, blind (PRA) bbnn Chocolate coat, blind (PRA) bbN_ Chocolate coat, normal vision Figure 9.9a

37. (b) A Labrador dihybrid cross Mating of double heterozygotes (black coat, normal vision) BbNn Phenotypic ratio of offspring 9 black coat, normal vision 3 black coat, blind (PRA) 3 chocolate coat, normal vision 1 chocolate coat, blind (PRA) Figure 9.9b

38. Using a Testcross to Determine an Unknown Genotype A testcross is a mating between –An individual of dominant phenotype (but unknown genotype) –A homozygous recessive individual © 2010 Pearson Education, Inc.

39. Two possible genotypes for the black dog: B_ bb Testcross Genotypes Bb B b or BB B b Bb bb b Gametes Offspring All black 1 black : 1 chocolate Figure 9.10

40. © 2010 Pearson Education, Inc. The Rules of Probability Mendel’s strong background in mathematics helped him understand patterns of inheritance. The rule of multiplication states that the probability of a compound event is the product of the separate probabilities of the independent events.

41. B B b B b b Female gametes B B B b b b Male gametes Formation of sperm Bb male Formation of eggs Bb female F 2 Genotypes F 1 Genotypes (  ) 1 2 1 4 1 2 1 2 1 2 1 4 1 4 1 4 1 2 1 2 Figure 9.11

42. © 2010 Pearson Education, Inc. Family Pedigrees Mendel’s principles apply to the inheritance of many human traits.

43. DOMINANT TRAITS Free earlobe RECESSIVE TRAITS Widow’s peakFreckles Attached earlobe Straight hairline No freckles Figure 9.12

44. Freckles No freckles Figure 9.12a

45. Widow’s peak Straight hairline Figure 9.12b

46. Free earlobeAttached earlobe Figure 9.12c

47. © 2010 Pearson Education, Inc. Dominant traits are not necessarily –Normal or –More common Wild-type traits are –Those seen most often in nature –Not necessarily specified by dominant alleles

48. © 2010 Pearson Education, Inc. A family pedigree –Shows the history of a trait in a family –Allows geneticists to analyze human traits

49. Female Male Attached Free Third generation (brother and sister) Second generation (parents, aunts, and uncles) First generation (grandparents) Ff FF ff or Ff ff FF or Ff ff Ff ff Figure 9.13

50. Figure 9.13a

51. Figure 9.13b

52. Figure 9.13c

53. © 2010 Pearson Education, Inc. Human Disorders Controlled by a Single Gene Many human traits –Show simple inheritance patterns –Are controlled by single genes on autosomes

54. Table 9.1

55. © 2010 Pearson Education, Inc. Recessive Disorders Most human genetic disorders are recessive. Individuals who have the recessive allele but appear normal are carriers of the disorder.

56. Parents Offspring Dd Hearing Dd Sperm Eggs D Hearing D Dd d Hearing (carrier) DD Dd Hearing (carrier) dd Deaf d Figure 9.14

57. © 2010 Pearson Education, Inc. Cystic fibrosis –Is the most common lethal genetic disease in the United States –Is caused by a recessive allele carried by about one in 25 people of European ancestry Prolonged geographic isolation of certain populations can lead to inbreeding, the mating of close relatives. –Inbreeding increases the chance of offspring that are homozygous for a harmful recessive trait.

58. © 2010 Pearson Education, Inc. Dominant Disorders Some human genetic disorders are dominant. –Huntington’s disease, which leads to degeneration of the nervous system, does not begin until middle age. –Achondroplasia is a form of dwarfism. –The homozygous dominant genotype causes death of the embryo. –Thus, only heterozygotes have this disorder.

59. Figure 9.15

60. Parents Sperm Eggs d Dwarf D Dd d dd d Normal (no achondroplasia) Molly Jo Dwarf (achondroplasia) Dd dd Normal dd Normal Dwarf Matt Amy JakeZachary Jeremy Figure 9.16

61. Parents Sperm Eggs d Dwarf D Dd d dd d Normal (no achondroplasia) Dwarf (achondroplasia) Dddd Normal dd Normal Dwarf Figure 9.16a

62. Molly Jo Matt Amy Jake Zachary Jeremy Figure 9.16b

63. © 2010 Pearson Education, Inc. The Process of Science: What Is the Genetic Basis of Hairless Dogs? Observation: Dogs come in a wide variety of physical types. Question: What is the genetic basis for the hairless phenotype? Hypothesis: A comparison of genes of coated and hairless dogs would identify the gene or genes responsible.

64. © 2010 Pearson Education, Inc. Prediction: A mutation in a single gene accounts for the hairless appearance. Experiment: Compared DNA sequences of 140 hairless dogs from 3 breeds with 87 coated dogs from 22 breeds. Results: Every hairless dog, but no coated dogs, had a single change in a single gene.

65. Figure 9.17

66. © 2010 Pearson Education, Inc. Genetic Testing Today many tests can detect the presence of disease-causing alleles. Most genetic testing is performed during pregnancy. –Amniocentesis collects cells from amniotic fluid. –Chorionic villus sampling removes cells from placental tissue. Genetic counseling helps patients understand the results and implications of genetic testing.

67. © 2010 Pearson Education, Inc. VARIATIONS ON MENDEL’S LAWS Some patterns of genetic inheritance are not explained by Mendel’s laws.

68. © 2010 Pearson Education, Inc. Incomplete Dominance in Plants and People In incomplete dominance, F 1 hybrids have an appearance in between the phenotypes of the two parents.

69. RRrr P Generation Gametes Red White R r Figure 9.18-1

70. F 1 Generation RRrr Gametes P Generation Gametes Red White R r Rr Pink R r 1 2 1 2 Figure 9.18-2

71. F 1 Generation RRrr Gametes P Generation F 2 Generation Sperm Gametes Red White R r Rr Pink R r R r R r RRRr rr Rr Eggs 1 2 1 2 1 2 1 2 1 2 1 2 Figure 9.18-3

72. © 2010 Pearson Education, Inc. Hypercholesterolemia –Is characterized by dangerously high levels of cholesterol in the blood. –Is a human trait that is incompletely dominant. –Heterozygotes have blood cholesterol levels about twice normal. –Homozygotes have blood cholesterol levels about five times normal.

73. Homozygous for ability to make LDL receptors Severe disease Mild disease Cell Normal LDL receptor LDL Homozygous for inability to make LDL receptors Heterozygous HH Hh hh GENOTYPE PHENOTYPE Figure 9.19

74. ABO Blood Groups: An Example of Multiple Alleles and Codominance The ABO blood groups in humans are an example of multiple alleles. © 2010 Pearson Education, Inc.

75. Blood Group (Phenotype) O Genotypes Antibodies Present in Blood Red Blood Cells Reactions When Blood from Groups Below Is Mixed with Antibodies from Groups at Left AB AB O A B ii IAIBIAIB I B or I B i I A or I A i Carbohydrate A Carbohydrate B Anti-A Anti-B Anti-A Anti-B — Figure 9.20

76. Blood Group (Phenotype) Genotypes Red Blood Cells O A B AB ii IAIBIAIB I B or I B i I A or I A i Carbohydrate A Carbohydrate B Figure 9.20a

77. O Antibodies Present in Blood Reactions When Blood from Groups Below Is Mixed with Antibodies from Groups at Left A B AB Anti-A Anti-B Anti-A Anti-B — Figure 9.20b

78. Figure 9.20

79. © 2010 Pearson Education, Inc. The immune system produces blood proteins called antibodies that can bind specifically to blood cell carbohydrates. Blood cells may clump together if blood cells of a different type enter the body. The clumping reaction is the basis of a blood-typing lab test.

80. Sickled cells can lead to a cascade of symptoms, such as weakness, pain, organ damage, and paralysis. Abnormal hemoglobin crystallizes into long flexible chains, causing red blood cells to become sickle-shaped. Individual homozygous, for sickle-cell allele Sickle-cell (abnormal) hemoglobin Colorized SEM Figure 9.21

82. © 2010 Pearson Education, Inc. The human blood type alleles I A and I B exhibit codominance: Both alleles are expressed in the phenotype.

83. © 2010 Pearson Education, Inc. Pleiotropy and Sickle-Cell Disease Pleiotropy is the impact of a single gene on more than one character. Sickle-cell disease –Exhibits pleiotropy –Results in abnormal hemoglobin production –Causes disk-shaped red blood cells to deform into a sickle shape with jagged edges

84. F 1 Generation Skin pigmentation P Generation F 2 Generation Sperm AABBCC (very dark) Eggs aabbcc (very light) AaBbCc Fraction of population 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 64 6 15 64 20 64 15 64 6 1 20 64 15 64 6 1 Figure 9.22

85. F 1 Generation P Generation F 2 Generation Sperm AABBCC (very dark) Eggs aabbcc (very light) AaBbCc 1 8 1 64 6 15 64 20 64 15 64 6 1 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 Figure 9.22a

86. Skin pigmentation Fraction of population 64 20 64 15 64 6 1 Figure 9.22b

87. © 2010 Pearson Education, Inc. Polygenic Inheritance Polygenic inheritance is the additive effects of two or more genes on a single phenotype.

88. Figure 9.23

89. © 2010 Pearson Education, Inc. The Role of Environment Many human characters result from a combination of heredity and environment. Only genetic influences are inherited.

90. F 1 Generation P Generation Round-yellow seeds (RRYY) Wrinkled-green seeds (rryy) Gametes MEIOSIS FERTILIZATION R R R Y Y Y y y y r r r All round-yellow seeds (RrYy) R r y Figure 9.24-1

91. F 1 Generation Law of Independent Assortment: Follow both the long and the short chromosomes. P Generation Round-yellow seeds (RRYY) Wrinkled-green seeds (rryy) Gametes MEIOSIS FERTILIZATION R R R Y Y Y y y y r r r All round-yellow seeds (RrYy) R r y Y MEIOSIS They are arranged in either of two equally likely ways at metaphase I. R r y Y R r y Y Metaphase I (alternative arrangements) Law of Segregation: Follow the long chromosomes (carrying R and r) taking either the left or right branch. Figure 9.24-2

92. F 1 Generation Law of Independent Assortment: Follow both the long and the short chromosomes. P Generation Gametes Round-yellow seeds (RRYY) Wrinkled-green seeds (rryy) Gametes MEIOSIS FERTILIZATION R R R Y Y Y y y y r r r All round-yellow seeds (RrYy) R r y Y MEIOSIS They are arranged in either of two equally likely ways at metaphase I. They sort independently, giving four gamete types. R r y Y R r yY R r y Y Metaphase I (alternative arrangements) Metaphase II r y R Y Law of Segregation: Follow the long chromosomes (carrying R and r) taking either the left or right branch. Only one long chromosome ends up in each gamete. The R and r alleles segregate in anaphase I of meiosis. R Y R Y R Y r y r r y Y r RY ry rY Ry 4 1 4 1 4 1 4 1 R y y Figure 9.24-3

93. F 1 Generation Law of Independent Assortment: Follow both the long and the short chromosomes. P Generation Gametes Round-yellow seeds (RRYY) Wrinkled-green seeds (rryy) Gametes MEIOSIS FERTILIZATION R R R Y Y Y y y y r r r All round-yellow seeds (RrYy) R r y Y MEIOSIS They are arranged in either of two equally likely ways at metaphase I. They sort independently, giving four gamete types. Fertilization results in the 9:3:3:1 phenotypic ratio in the F 2 generation. R r y Y R r yY R r y Y Metaphase I (alternative arrangements) Metaphase II r y R Y Law of Segregation: Follow the long chromosomes (carrying R and r) taking either the left or right branch. Only one long chromosome ends up in each gamete. The R and r alleles segregate in anaphase I of meiosis. R Y R Y R Y r y r y r y Y r Fertilization recombines the r and R alleles at random. F 2 Generation RY ry rY Ry 9 : 3 : 1 FERTILIZATION AMONG THE F 1 PLANTS 4 1 4 1 4 1 4 1 R y Figure 9.24-4

94. © 2010 Pearson Education, Inc. THE CHROMOSOMAL BASIS OF INHERITANCE The chromosome theory of inheritance states that –Genes are located at specific positions on chromosomes –The behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns It is chromosomes that undergo segregation and independent assortment during meiosis and thus account for Mendel’s laws.

95. Dihybrid testcross Gray body, long wings (wild-type) Female GgLl Black body, short wings (mutant) Male ggll Figure 9.25-1

96. Dihybrid testcross Results Gray body, long wings (wild-type) Female GgLl Black body, short wings (mutant) Male ggll Parental phenotypes 83% Gray-long GgLl Black-short ggll Offspring Gray-short Ggll Black-long ggLl 965 944 Recombinant phenotypes 17% 206 185 Figure 9.25-2

97. © 2010 Pearson Education, Inc. Linked Genes Linked genes –Are located close together on a chromosome –May be inherited together Using the fruit fly Drosophila melanogaster, Thomas Hunt Morgan determined that some genes were linked based on the inheritance patterns of their traits.

98. Crossing over Pair of homologous chromosomes A Recombinant gametes B A B ab a b Parental gametes A Ba b Figure 9.26

99. © 2010 Pearson Education, Inc. Genetic Recombination: Crossing Over Crossing over can –Separate linked alleles –Produce gametes with recombinant chromosomes –Produce offspring with recombinant phenotypes

100. Crossing over Recombinant gametes Parental gametes GgLl (female) G L g l G L g l G l g L ggll (male) g l Sperm Recombinant Parental Eggs Offspring FERTILIZATION G L g l g L g l G l g l Figure 9.27

101. Crossing over Recombinant gametes Parental gametes GgLl (female) G L g l G l g L ggll (male) g g l Sperm Eggs l g l g l Figure 9.27a

102. Recombinant gametes Parental gametes G L g l G lg L g l Sperm Recombinant Parental Eggs Offspring FERTILIZATION G L g l g L g l G l g l Figure 9.27b

103. © 2010 Pearson Education, Inc. The percentage of recombinant offspring among the total is called the recombination frequency.

104. Chromosome gc Recombination frequencies l 17% 9.5% 9% Figure 9.28

105. © 2010 Pearson Education, Inc. Linkage Maps Early studies of crossing over were performed using the fruit fly Drosophila melanogaster. Alfred H. Sturtevant, a student of Morgan, developed a method for mapping gene loci, which resulted in the creation of linkage maps. –A diagram of relative gene locations on a chromosome is a linkage map.

106. Male Sperm Somatic cells 44  XY 44  XX Female 22  X 44  XY 44  XX 22  Y Egg 22  X Male Female Offspring Figure 9.29

107. Colorized SEM Y X Figure 9.29

108. © 2010 Pearson Education, Inc. SEX CHROMOSOMES AND SEX-LINKED GENES Sex chromosomes influence the inheritance of certain traits.

109. © 2010 Pearson Education, Inc. Sex Determination in Humans Nearly all mammals have a pair of sex chromosomes designated X and Y. –Males have an X and Y. –Females have XX.

110. © 2010 Pearson Education, Inc. Sex-Linked Genes Any gene located on a sex chromosome is called a sex-linked gene. –Most sex-linked genes are found on the X chromosome. –Red-green color blindness is a common human sex-linked disorder.

111. Figure 9.30

112. Unaffected individual Sperm Eggs XNXNXNXN XnYXnY XnXn Y Sperm XNXnXNXn XNYXNY XNXN Y XNXnXNXn XnYXnY XnXn Y XNXnXNXn XNYXNY XNXN XNXN XNXnXNXn XNYXNY Eggs XNXNXNXN XNYXNY XNXN XnXn XnYXnY XNXnXNXn XNXnXNXn XNYXNY XNXN XnXn XnYXnY XnXnXnXn Normal female  colorblind male Key (a) Carrier female  normal male (b) Carrier female  colorblind male (c) Colorblind individual Carrier Figure 9.31

113. © 2010 Pearson Education, Inc. Hemophilia –Is a sex-linked recessive blood-clotting trait that may result in excessive bleeding and death after relatively minor cuts and bruises –Has plagued royal families of Europe

114. Albert Queen Victoria Alice Louis Alexandra Czar Nicholas II of Russia Alexis Figure 9.32

115. Evolution Connection: Barking Up the Evolutionary Tree About 15,000 years ago in East Asia, humans began to cohabit with ancestral canines that were predecessors of modern wolves and dogs. As people settled into geographically distinct populations, different canines became separated and inbred. © 2010 Pearson Education, Inc.

116. In 2005 researchers sequenced the complete genome of a dog. An evolutionary tree of dog breeds was created.

117. Chinese shar-pei Ancestral canine Wolf Akita Basenji Siberian husky Alaskan malamute Afghan hound Rottweiler Saluki Sheepdog Retriever Figure 9.33

118. Meiosis Haploid gametes (allele pairs separate) Diploid cell (contains paired alleles, alternate forms of a gene) Diploid zygote (contains paired alleles) Gamete from other parent Alleles Fertilization Figure 9.UN1

119. Phenotype P ? Phenotype Genotype Conclusion Recessive Dominant pp All dominant or Unknown parent is PP 1 dominant : 1 recessive Unknown parent is Pp Figure 9.UN2

120. Dominant phenotype (RR) Recessive phenotype (rr) Intermediate phenotype (incomplete dominance) (Rr) Figure 9.UN3

121. Pleiotropy Multiple traits (e.g., sickle-cell disease) Single gene Figure 9.UN4

122. Multiple genes Polygenic inheritance Single trait (e.g., skin color) Figure 9.UN5

123. Female Somatic cells Male 44  XY 44  XX Figure 9.UN6

124. Figure 9.UN7

125. Figure 9.UN8