1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 9 Patterns of Inheritance

2.  Dogs are one of man’s longest genetic experiments. –Over thousands of years, humans have chosen and mated dogs with specific traits. –The result has been an incredibly diverse array of dogs with distinct –body types and –behavioral traits. Introduction © 2012 Pearson Education, Inc.

3. Figure 9.0_1 Chapter 9: Big Ideas Mendel’s LawsVariations on Mendel’s Laws The Chromosomal Basis of Inheritance Sex Chromosomes and Sex-Linked Genes

4. Figure 9.0_2

5. MENDEL’S LAWS © 2012 Pearson Education, Inc.

6. 9.1 The science of genetics has ancient roots  Pangenesis, proposed around 400 BCE by Hippocrates, was an early explanation for inheritance that suggested that –particles called pangenes came from all parts of the organism to be incorporated into eggs or sperm and –characteristics acquired during the parents’ lifetime could be transferred to the offspring.  Aristotle rejected pangenesis and argued that instead of particles, the potential to produce the traits was inherited. © 2012 Pearson Education, Inc.

7. Figure 9.1

8. 9.1 The science of genetics has ancient roots  The idea that hereditary materials mix in forming offspring, called the blending hypothesis, was –suggested in the 19th century by scientists studying plants but –later rejected because it did not explain how traits that disappear in one generation can reappear in later generations. © 2012 Pearson Education, Inc.

9. 9.2 Experimental genetics began in an abbey garden  Heredity is the transmission of traits from one generation to the next.  Genetics is the scientific study of heredity.  Gregor Mendel –began the field of genetics in the 1860s, –deduced the principles of genetics by breeding garden peas, and –relied upon a background of mathematics, physics, and chemistry. © 2012 Pearson Education, Inc.

10. 9.2 Experimental genetics began in an abbey garden  In 1866, Mendel –correctly argued that parents pass on to their offspring discrete “heritable factors” and –stressed that the heritable factors (today called genes), retain their individuality generation after generation.  A heritable feature that varies among individuals, such as flower color, is called a character.  Each variant for a character, such as purple or white flowers, is a trait. © 2012 Pearson Education, Inc.

11. Figure 9.2A

12. 9.2 Experimental genetics began in an abbey garden  True-breeding varieties result when self-fertilization produces offspring all identical to the parent.  The offspring of two different varieties are hybrids.  The cross-fertilization is a hybridization, or genetic cross.  True-breeding parental plants are the P generation.  Hybrid offspring are the F 1 generation.  A cross of F 1 plants produces an F 2 generation. © 2012 Pearson Education, Inc.

13. Figure 9.2B Stamen Carpel Petal

14. Figure 9.2C_s1 Removal of stamens Carpel White Stamens Transfer of pollen Purple Parents (P) 2 1

15. Figure 9.2C_s2 Removal of stamens Carpel White Stamens Transfer of pollen Purple Carpel matures into pea pod Parents (P) 2 3 1

16. Figure 9.2C_s3 Removal of stamens Carpel White Stamens Transfer of pollen Purple Carpel matures into pea pod Seeds from pod planted Offspring (F 1 ) Parents (P) 2 3 1 4

17. Figure 9.2D Character Traits Dominant Recessive Flower color PurpleWhite Flower position Axial Terminal Seed color YellowGreen Seed shape Round Wrinkled Pod shape InflatedConstricted Pod color GreenYellow Stem length Tall Dwarf

18. Figure 9.2D_1 Character Traits Dominant Recessive Flower color Purple White Flower position Axial Terminal Seed color Yellow Green Seed shape RoundWrinkled

19. Figure 9.2D_2 Character Dominant Recessive Traits Pod shape Inflated Constricted Pod color GreenYellow Stem length Tall Dwarf

20. 9.3 Mendel’s law of segregation describes the inheritance of a single character  A cross between two individuals differing in a single character is a monohybrid cross.  Mendel performed a monohybrid cross between a plant with purple flowers and a plant with white flowers. –The F 1 generation produced all plants with purple flowers. –A cross of F 1 plants with each other produced an F 2 generation with ¾ purple and ¼ white flowers. © 2012 Pearson Education, Inc.

21. Figure 9.3A_s1 The Experiment P generation (true-breeding parents) Purple flowers White flowers 

22. Figure 9.3A_s2 The Experiment P generation (true-breeding parents) F 1 generation Purple flowers White flowers All plants have purple flowers 

23. Figure 9.3A_s3 The Experiment P generation (true-breeding parents) F 1 generation F 2 generation of plants have purple flowers of plants have white flowers Purple flowers White flowers All plants have purple flowers Fertilization among F 1 plants (F 1  F 1 )  3 4 1 4

24. 9.3 Mendel’s law of segregation describes the inheritance of a single character  The all-purple F 1 generation did not produce light purple flowers, as predicted by the blending hypothesis.  Mendel needed to explain why –white color seemed to disappear in the F 1 generation and –white color reappeared in one quarter of the F 2 offspring.  Mendel observed the same patterns of inheritance for six other pea plant characters. © 2012 Pearson Education, Inc.

25. 9.3 Mendel’s law of segregation describes the inheritance of a single character  Mendel developed four hypotheses, described below using modern terminology. 1. Alleles are alternative versions of genes that account for variations in inherited characters. 2. For each characteristic, an organism inherits two alleles, one from each parent. The alleles can be the same or different. –A homozygous genotype has identical alleles. –A heterozygous genotype has two different alleles. © 2012 Pearson Education, Inc.

26. 9.3 Mendel’s law of segregation describes the inheritance of a single character 3.If the alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele. The other has no noticeable effect on the organism’s appearance and is called the recessive allele. –The phenotype is the appearance or expression of a trait. –The genotype is the genetic makeup of a trait. –The same phenotype may be determined by more than one genotype. © 2012 Pearson Education, Inc.

27. 9.3 Mendel’s law of segregation describes the inheritance of a single character 4.A sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes. This statement is called the law of segregation.  Mendel’s hypotheses also explain the 3:1 ratio in the F 2 generation. –The F 1 hybrids all have a Pp genotype. –A Punnett square shows the four possible combinations of alleles that could occur when these gametes combine. © 2012 Pearson Education, Inc.

28. Figure 9.3B_s1 The Explanation P generation Genetic makeup (alleles) Purple flowers White flowers Gametes All p pp PP PAll

29. Figure 9.3B_s2 The Explanation P generation F 1 generation (hybrids) Genetic makeup (alleles) Purple flowers White flowers Gametes All p pp PP P p Gametes All Pp 2 1 2 1 PAll

30. Figure 9.3B_s3 The Explanation P generation F 1 generation (hybrids) F 2 generation Genetic makeup (alleles) Purple flowers White flowers Gametes P All p pp PP P P P p p p Pp pp Eggs from F 1 plant Gametes Fertilization All Pp Alleles segregate Phenotypic ratio 3 purple : 1 white Genotypic ratio 1 PP : 2 Pp : 1 pp Sperm from F 1 plant 2 1 2 1 All

31. Figure 9.3B_4 F 2 generation 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 Sperm from F 1 plant

32. 9.4 Homologous chromosomes bear the alleles for each character  A locus (plural, loci) is the specific location of a gene along a chromosome.  For a pair of homologous chromosomes, alleles of a gene reside at the same locus. –Homozygous individuals have the same allele on both homologues. –Heterozygous individuals have a different allele on each homologue. © 2012 Pearson Education, Inc.

33. Figure 9.4 P P a a B b PP aa Bb Dominant allele Recessive allele Gene loci Homologous chromosomes Genotype: Heterozygous, with one dominant and one recessive allele Homozygous for the recessive allele Homozygous for the dominant allele

34. 9.5 The law of independent assortment is revealed by tracking two characters at once  A dihybrid cross is a mating of parental varieties that differ in two characters.  Mendel performed the following dihybrid cross with the following results: –P generation: round yellow seeds  wrinkled green seeds –F 1 generation: all plants with round yellow seeds –F 2 generation: –9/16 had round yellow seeds –3/16 had wrinkled yellow seeds –3/16 had round green seeds –1/16 had wrinkled green seeds © 2012 Pearson Education, Inc.

35. Figure 9.5A 4 1 4 1 4 1 4 1 4 1 4 1 4 1 4 1 16 9 3 3 1 2 1 2 1 2 1 2 1 F 1 generation F 2 generation P generation Gametes Sperm Eggs Yellow round Green round Yellow wrinkled Green wrinkled  RRYY rryy RY ry RrYy The hypothesis of dependent assortment Data did not support; hypothesis refuted The hypothesis of independent assortment Actual results; hypothesis supported RY ry Eggs RY rY Ry ry RRYY RrYYRRYyRrYy RrYY rrYY RrYy rrYy RRYyRrYyRRyyRryy RrYyrrYyRryy rryy Sperm

36. Figure 9.5A_1 F 1 generation P generation Gametes  RRYY rryy RY ry RrYy

37. Figure 9.5A_2 2 1 F 2 generation The hypothesis of dependent assortment Data did not support; hypothesis refuted RY ry Eggs Sperm 2 1 2 1 2 1 F 1 generation RrYy

38. Figure 9.5A_3 4 1 Sperm Eggs Yellow round Green round Yellow wrinkled Green wrinkled The hypothesis of independent assortment Actual results; hypothesis supported RY rY Ry ry RRYY RrYY RRYy RrYy RrYY rrYY RrYy rrYy RRYy RrYy RRyy Rryy RrYyrrYy Rryy rryy 4 1 4 1 4 1 4 1 4 1 4 1 4 1 16 9 3 1 F 1 generation RrYy 16 3

39. Figure 9.5B Phenotypes Genotypes Black coat, normal vision B_N_ Black coat, blind (PRA) B_nn Blind Chocolate coat, normal vision bbN_ Blind Chocolate coat, blind (PRA) bbnn Mating of double heterozygotes (black coat, normal vision) BbNn  Phenotypic ratio of the offspring 9 Black coat, normal vision 3 Black coat, blind (PRA) 1 Chocolate coat, blind (PRA) 3 Chocolate coat, normal vision

40. Figure 9.5B_1 Phenotypes Genotypes Phenotypes Genotypes Blind Black coat, normal vision B_N_ Black coat, blind (PRA) B_nn Chocolate coat, normal vision bbN_ Chocolate coat, blind (PRA) bbnn

41. Figure 9.5B_2 Blind Mating of double heterozygotes (black coat, normal vision) BbNn  Phenotypic ratio of the offspring 9 Black coat, normal vision 3 Black coat, blind (PRA) 1 Chocolate coat, blind (PRA) 3 Chocolate coat, normal vision

42. 9.5 The law of independent assortment is revealed by tracking two characters at once  Mendel needed to explain why the F 2 offspring –had new nonparental combinations of traits and –a 9:3:3:1 phenotypic ratio.  Mendel –suggested that the inheritance of one character has no effect on the inheritance of another, –suggested that the dihybrid cross is the equivalent to two monohybrid crosses, and –called this the law of independent assortment. © 2012 Pearson Education, Inc.

43. 9.5 The law of independent assortment is revealed by tracking two characters at once  The following figure demonstrates the law of independent assortment as it applies to two characters in Labrador retrievers: –black versus chocolate color, –normal vision versus progressive retinal atrophy. © 2012 Pearson Education, Inc.

44. 9.6 Geneticists can use the testcross to determine unknown genotypes  A testcross is the mating between an individual of unknown genotype and a homozygous recessive individual.  A testcross can show whether the unknown genotype includes a recessive allele.  Mendel used testcrosses to verify that he had true- breeding genotypes.  The following figure demonstrates how a testcross can be performed to determine the genotype of a Lab with normal eyes. © 2012 Pearson Education, Inc.

45. Figure 9.6 What is the genotype of the black dog? Two possibilities for the black dog:  Testcross Genotypes Gametes Offspring All black 1 black : 1 chocolate or B_? bb Bb BB B B b b b Bb bb

46. 9.7 Mendel’s laws reflect the rules of probability  Using his strong background in mathematics, Mendel knew that the rules of mathematical probability affected –the segregation of allele pairs during gamete formation and –the re-forming of pairs at fertilization.  The probability scale ranges from 0 to 1. An event that is –certain has a probability of 1 and –certain not to occur has a probability of 0. © 2012 Pearson Education, Inc.

47. 9.7 Mendel’s laws reflect the rules of probability  The probability of a specific event is the number of ways that event can occur out of the total possible outcomes.  Determining the probability of two independent events uses the rule of multiplication, in which the probability is the product of the probabilities for each event.  The probability that an event can occur in two or more alternative ways is the sum of the separate probabilities, called the rule of addition. © 2012 Pearson Education, Inc.

48. Figure 9.7 F 1 genotypes Formation of eggs Formation of sperm Bb female Bb male Sperm F 2 genotypes Eggs B B B BB B b b b b b b  2 1 2 1 2 1 2 1 2 1 2 1 4 1 4 1 4 1 4 1 ( )

49. 9.8 CONNECTION: Genetic traits in humans can be tracked through family pedigrees  In a simple dominant-recessive inheritance of dominant allele A and recessive allele a, –a recessive phenotype always results from a homozygous recessive genotype (aa) but –a dominant phenotype can result from either –the homozygous dominant genotype (AA) or –a heterozygous genotype (Aa).  Wild-type traits, those prevailing in nature, are not necessarily specified by dominant alleles. © 2012 Pearson Education, Inc.

50. Figure 9.8A Dominant Traits Recessive Traits Freckles No freckles Widow’s peak Straight hairline Free earlobe Attached earlobe

51. Figure 9.8A_1 Freckles

52. Figure 9.8A_2 No freckles

53. Figure 9.8A_3 Widow’s peak

54. Figure 9.8A_4 Straight hairline

55. Figure 9.8A_5 Free earlobe

56. Figure 9.8A_6 Attached earlobe

57. 9.8 CONNECTION: Genetic traits in humans can be tracked through family pedigrees  The inheritance of human traits follows Mendel’s laws.  A pedigree –shows the inheritance of a trait in a family through multiple generations, –demonstrates dominant or recessive inheritance, and –can also be used to deduce genotypes of family members. © 2012 Pearson Education, Inc.

58. Figure 9.8B First generation (grandparents) Second generation (parents, aunts, and uncles) Third generation (two sisters) Female Male Attached Free Ff ff Ff ff FF or Ff

59. 9.9 CONNECTION: Many inherited disorders in humans are controlled by a single gene  Inherited human disorders show either 1.recessive inheritance in which –two recessive alleles are needed to show disease, –heterozygous parents are carriers of the disease-causing allele, and –the probability of inheritance increases with inbreeding, mating between close relatives. 2.dominant inheritance in which –one dominant allele is needed to show disease and –dominant lethal alleles are usually eliminated from the population. © 2012 Pearson Education, Inc.

60. Figure 9.9A Parents Offspring Sperm Eggs Normal Dd  D D d d DD Normal Dd Normal (carrier) dd Deaf

61. 9.9 CONNECTION: Many inherited disorders in humans are controlled by a single gene  The most common fatal genetic disease in the United States is cystic fibrosis (CF), resulting in excessive thick mucus secretions. The CF allele is –recessive and –carried by about 1 in 31 Americans.  Dominant human disorders include –achondroplasia, resulting in dwarfism, and –Huntington’s disease, a degenerative disorder of the nervous system. © 2012 Pearson Education, Inc.

62. Table 9.9

63. Figure 9.9B

64.  New technologies offer ways to obtain genetic information –before conception, –during pregnancy, and –after birth.  Genetic testing can identify potential parents who are heterozygous carriers for certain diseases. 9.10 CONNECTION: New technologies can provide insight into one’s genetic legacy © 2012 Pearson Education, Inc.

65.  Several technologies can be used for detecting genetic conditions in a fetus. –Amniocentesis extracts samples of amniotic fluid containing fetal cells and permits –karyotyping and –biochemical tests on cultured fetal cells to detect other conditions, such as Tay-Sachs disease. –Chorionic villus sampling removes a sample of chorionic villus tissue from the placenta and permits similar karyotyping and biochemical tests. 9.10 CONNECTION: New technologies can provide insight into one’s genetic legacy © 2012 Pearson Education, Inc.

66. Video: Ultrasound of Human Fetus Use windows controls to play

67. Figure 9.10A Amniocentesis Ultrasound transducer Fetus Placenta Uterus Cervix Amniotic fluid extracted Centrifugation Amniotic fluid Fetal cells Cultured cells Several hours Several weeks Biochemical and genetics tests Several hours Fetal cells Cervix Uterus Chorionic villi Placenta Fetus Ultrasound transducer Tissue extracted from the chorionic villi Chorionic Villus Sampling (CVS) Karyotyping

68.  Blood tests on the mother at 14–20 weeks of pregnancy can help identify fetuses at risk for certain birth defects.  Fetal imaging enables a physician to examine a fetus directly for anatomical deformities. The most common procedure is ultrasound imaging, using sound waves to produce a picture of the fetus.  Newborn screening can detect diseases that can be prevented by special care and precautions. 9.10 CONNECTION: New technologies can provide insight into one’s genetic legacy © 2012 Pearson Education, Inc.

69. Figure 9.10B

70. Figure 9.10B_1

71. Figure 9.10B_2

72.  New technologies raise ethical considerations that include –the confidentiality and potential use of results of genetic testing, –time and financial costs, and –determining what, if anything, should be done as a result of the testing. 9.10 CONNECTION: New technologies can provide insight into one’s genetic legacy © 2012 Pearson Education, Inc.

73. VARIATIONS ON MENDEL’S LAWS © 2012 Pearson Education, Inc.

74. 9.11 Incomplete dominance results in intermediate phenotypes  Mendel’s pea crosses always looked like one of the parental varieties, called complete dominance.  For some characters, the appearance of F 1 hybrids falls between the phenotypes of the two parental varieties. This is called incomplete dominance, in which –neither allele is dominant over the other and –expression of both alleles occurs. © 2012 Pearson Education, Inc.

75. Figure 9.11A P generation F 1 generation F 2 generation 2 1 2 1 2 1 2 1 2 1 2 1 Gametes Eggs Sperm  Red RR White rr Pink hybrid Rr R R R R r r r r RR rR Rrrr

76. Figure 9.11A_1 P generation Gametes  Red RR White rr R r

77. Figure 9.11A_2 F 1 generation 2 1 Gametes Pink hybrid Rr R r 2 1

78. 2 1 2 1 2 1 2 1 Figure 9.11A_3 F 2 generation Eggs Sperm R R r r RR rR Rr rr

79. 9.11 Incomplete dominance results in intermediate phenotypes  Incomplete dominance does not support the blending hypothesis because the original parental phenotypes reappear in the F 2 generation.  One example of incomplete dominance in humans is hypercholesterolemia, in which –dangerously high levels of cholesterol occur in the blood and –heterozygotes have intermediately high cholesterol levels. © 2012 Pearson Education, Inc.

80. Figure 9.11B Normal Mild disease Severe disease Phenotypes Cell LDL receptor LDL HH Homozygous for ability to make LDL receptors hh Homozygous for inability to make LDL receptors Genotypes Hh Heterozygous

81. 9.12 Many genes have more than two alleles in the population  Although an individual can at most carry two different alleles for a particular gene, more than two alleles often exist in the wider population.  Human ABO blood group phenotypes involve three alleles for a single gene.  The four human blood groups, A, B, AB, and O, result from combinations of these three alleles.  The A and B alleles are both expressed in heterozygous individuals, a condition known as codominance. © 2012 Pearson Education, Inc.

82. 9.12 Many genes have more than two alleles in the population  In codominance, –neither allele is dominant over the other and –expression of both alleles is observed as a distinct phenotype in the heterozygous individual. –AB blood type is an example of codominance. © 2012 Pearson Education, Inc.

83. Figure 9.12 Blood Group (Phenotype) Genotypes Carbohydrates Present on Red Blood Cells Antibodies Present in Blood A B AB O I A I A or I A i I B I B or I B i IAIBIAIB ii Carbohydrate A Carbohydrate B Carbohydrate A and Carbohydrate B Neither Anti-B Anti-A Anti-B Anti-A None No reaction Clumping reaction OABAB Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left

84. Figure 9.12_1 Blood Group (Phenotype) Genotypes Carbohydrates Present on Red Blood Cells A B AB O I A I A or I A i I B I B or I B i IAIBIAIB ii Carbohydrate A Carbohydrate B Carbohydrate A and Carbohydrate B Neither

85. Figure 9.12_2 Antibodies Present in Blood Anti-B Anti-A Anti-B Anti-A None O A B AB Reaction When Blood from Groups Below Is Mixed with Antibodies from Groups at Left Blood Group (Phenotype) A B AB O

86. 9.13 A single gene may affect many phenotypic characters  Pleiotropy occurs when one gene influences many characteristics.  Sickle-cell disease is a human example of pleiotropy. This disease –affects the type of hemoglobin produced and the shape of red blood cells and –causes anemia and organ damage. –Sickle-cell and nonsickle alleles are codominant. –Carriers of sickle-cell disease are resistant to malaria. © 2012 Pearson Education, Inc.

87. Figure 9.13A

88. Figure 9.13B An individual homozygous for the sickle-cell allele Produces sickle-cell (abnormal) hemoglobin The abnormal hemoglobin crystallizes, causing red blood cells to become sickle-shaped Sickled cell The multiple effects of sickled cells Damage to organs Other effects Kidney failure Heart failure Spleen damage Brain damage (impaired mental function, paralysis) Pain and fever Joint problems Physical weakness Anemia Pneumonia and other infections

89. 9.14 A single character may be influenced by many genes  Many characteristics result from polygenic inheritance, in which a single phenotypic character results from the additive effects of two or more genes.  Human skin color is an example of polygenic inheritance. © 2012 Pearson Education, Inc.

90. Figure 9.14 P generation F 1 generation F 2 generation Eggs Sperm Skin color Fraction of population aabbcc (very light) AABBCC (very dark) AaBbCc   8 1 64 15 64 20 64 6 1 15 64 6 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

91. Figure 9.14_1 P generation F 1 generation aabbcc (very light) AABBCC (very dark) AaBbCc  

92. Figure 9.14_2 F 2 generation Eggs Sperm 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 1 6 15 64 20 64 1 6 15

93. Figure 9.14_3 Skin color Fraction of population 64 20 64 15 64 6 1

94. 9.15 The environment affects many characters  Many characters result from a combination of heredity and the environment. For example, –skin color is affected by exposure to sunlight, –susceptibility to diseases, such as cancer, has hereditary and environmental components, and –identical twins show some differences.  Only genetic influences are inherited. © 2012 Pearson Education, Inc.

95. Figure 9.15A

96. Figure 9.15B

97. THE CHROMOSOMAL BASIS OF INHERITANCE © 2012 Pearson Education, Inc.

98. 9.16 Chromosome behavior accounts for Mendel’s laws  The chromosome theory of inheritance states that –genes occupy specific loci (positions) on chromosomes and –chromosomes undergo segregation and independent assortment during meiosis. © 2012 Pearson Education, Inc.

99. 9.16 Chromosome behavior accounts for Mendel’s laws  Mendel’s laws correlate with chromosome separation in meiosis. –The law of segregation depends on separation of homologous chromosomes in anaphase I. –The law of independent assortment depends on alternative orientations of chromosomes in metaphase I. © 2012 Pearson Education, Inc.

100. Figure 9.16_s1 F 1 generation All yellow round seeds (RrYy) Meta- phase I of meiosis Yy R r r r R R Y Y y y

101. Figure 9.16_s2 F 1 generation All yellow round seeds (RrYy) Meta- phase I of meiosis Anaphase I Metaphase II R y r Y Y R r y Y Y y y R R r r r r r R R R Y Y Y y y y

102. Figure 9.16_s3 F 1 generation 4 1 4 1 4 1 4 1 All yellow round seeds (RrYy) Meta- phase I of meiosis Anaphase I Metaphase II Fertilization Gametes F 2 generation 9 :3 :1 RY ry rY Ry R R R y y y rr r Y Y Y Y Y Y R R R r r r y y y Y Y y y R R r r r r r R R R Y Y Y y y y

103. Figure 9.16_4 Sperm Eggs Yellow round Green round Yellow wrinkled Green wrinkled RY rY Ry ry RRYY RrYY RRYy RrYy RrYY rrYY RrYy rrYy RRYyRrYy RRyy Rryy RrYy rrYyRryy rryy 4 1 16 9 3 3 1 4 1 4 1 4 1 4 1 4 1 4 1 4 1

104. 9.17 SCIENTIFIC DISCOVERY: Genes on the same chromosome tend to be inherited together  Bateson and Punnett studied plants that did not show a 9:3:3:1 ratio in the F 2 generation. What they found was an example of linked genes, which –are located close together on the same chromosome and –tend to be inherited together. © 2012 Pearson Education, Inc.

105. Figure 9.17 The Experiment Purple flower Long pollen  PpLl PhenotypesObserved offspring Prediction (9:3:3:1) Purple long Purple round Red long Red round 284 21 55 215 71 24 The Explanation: Linked Genes Parental diploid cell PpLl Meiosis P L p l Most gametes Fertilization Sperm Most offspring Eggs 3 purple long : 1 red round Not accounted for: purple round and red long P L p l

106. Figure 9.17_1 The Experiment Purple flower Long pollen  PpLl Phenotypes Observed offspring Prediction (9:3:3:1) Purple long Purple round Red long Red round 284 21 55 215 71 24

107. Figure 9.17_2 The Explanation: Linked Genes Parental diploid cell PpLl Meiosis P L p l Most gametes Fertilization Sperm Most offspring Eggs 3 purple long : 1 red round Not accounted for: purple round and red long P L p l

108. 9.18 SCIENTIFIC DISCOVERY: Crossing over produces new combinations of alleles  Crossing over between homologous chromosomes produces new combinations of alleles in gametes.  Linked alleles can be separated by crossing over, forming recombinant gametes.  The percentage of recombinants is the recombination frequency. © 2012 Pearson Education, Inc.

109. Figure 9.18A P L Tetrad (pair of homologous chromosomes) p l p L P l Crossing over Parental gametes Recombinant gametes

110. Figure 9.18B

111. Figure 9.18C The Experiment Female Male ggll GgLl Black body, vestigial wings Gray body, long wings (wild type) Offspring Gray long Black vestigialGray vestigial Black long Recombinant phenotypes Parental phenotypes Recombination frequency  0.17 or 17% 391 recombinants 2,300 total offspring 965944206185 Offspring ParentalRecombinant EggsSperm Crossing over G L g l G lg L G L g l G l g Lg L g l The Explanation GgLl Female ggll Male G L

112. Figure 9.18C_1 The Experiment Female Male ggll GgLl Black body, vestigial wings Gray body, long wings (wild type) Offspring: Gray long Black vestigialGray vestigial Black long Recombinant phenotypes Parental phenotypes Recombination frequency  0.17 or 17% 391 recombinants 2,300 total offspring 965 944 206185

113. Figure 9.18C_2 Offspring Parental Recombinant Eggs Sperm Crossing over G L g l G l g L G L g l G l g L g l The Explanation GgLl Female ggll Male G L

114. 9.19 Geneticists use crossover data to map genes  When examining recombinant frequency, Morgan and his students found that the greater the distance between two genes on a chromosome, the more points there are between them where crossing over can occur.  Recombination frequencies can thus be used to map the relative position of genes on chromosomes. © 2012 Pearson Education, Inc.

115. Figure 9.19A Section of chromosome carrying linked genes Recombination frequencies 17% 9%9.5% g cl

116. Figure 9.19B Mutant phenotypes Short aristae Black body (g) Cinnabar eyes (c) Vestigial wings (l) Brown eyes Red eyes Normal wings (L) Red eyes (C) Gray body (G) Long aristae (appendages on head) Wild-type phenotypes

117. SEX CHROMOSOMES AND SEX-LINKED GENES © 2012 Pearson Education, Inc.

118. 9.20 Chromosomes determine sex in many species  Many animals have a pair of sex chromosomes, –designated X and Y, –that determine an individual’s sex.  In mammals, –males have XY sex chromosomes, –females have XX sex chromosomes, –the Y chromosome has genes for the development of testes, and –an absence of the Y allows ovaries to develop. © 2012 Pearson Education, Inc.

119. Figure 9.20A X Y

120. Figure 9.20B Parents (diploid) Gametes (haploid) Offspring (diploid) Female Male Egg Sperm 44  XY 44  XX 22  X 22  Y 22  X 44  XX 44  XY

121. Figure 9.20B_1

122. 9.20 Chromosomes determine sex in many species  Grasshoppers, roaches, and some other insects have an X-O system, in which –O stands for the absence of a sex chromosome, –females are XX, and –males are XO.  In certain fishes, butterflies, and birds, –the sex chromosomes are Z and W, –males are ZZ, and –females are ZW. © 2012 Pearson Education, Inc.

123. Figure 9.20C 22  XX 22  X Male Female

124. Figure 9.20C_1

125. Figure 9.20D 76  ZW 76  ZZ Male Female

126. Figure 9.20D_1

127. 9.20 Chromosomes determine sex in many species  Some organisms lack sex chromosomes altogether.  In bees, sex is determined by chromosome number. –Females are diploid. –Males are haploid. © 2012 Pearson Education, Inc.

128. Figure 9.20E Male Female 16 32

129. Figure 9.20E_1

130. 9.20 Chromosomes determine sex in many species  In some animals, environmental temperature determines the sex. –For some species of reptiles, the temperature at which the eggs are incubated during a specific period of development determines whether the embryo will develop into a male or female. –Global climate change may therefore impact the sex ratio of such species. © 2012 Pearson Education, Inc.

131.  Sex-linked genes are located on either of the sex chromosomes.  The X chromosome carries many genes unrelated to sex.  The inheritance of white eye color in the fruit fly illustrates an X-linked recessive trait. 9.21 Sex-linked genes exhibit a unique pattern of inheritance © 2012 Pearson Education, Inc.

132. Figure 9.21A

133. Figure 9.21A_1

134. Figure 9.21A_2

135. Figure 9.21B Male Female Sperm Eggs R  red-eye allele r  white-eye allele XRXR XrXr XrYXrY XRXRXRXR XRXrXRXr XRYXRY Y

136. Figure 9.21C R  red-eye allele r  white-eye allele Male Female Sperm Eggs XRXR xRxR XRYXRY XRXrXRXr Y XrXr XrYXrY XRYXRY XRXRXRXR XrXRXrXR

137. Figure 9.21D R  red-eye allele r  white-eye allele Male Female Sperm Eggs XrYXrY XRXrXRXr XrXrXrXr XrXr XRXR XrXr Y XrYXrY XRYXRY XRXrXRXr

138. 9.22 CONNECTION: Human sex-linked disorders affect mostly males  Most sex-linked human disorders are –due to recessive alleles and –seen mostly in males.  A male receiving a single X-linked recessive allele from his mother will have the disorder.  A female must receive the allele from both parents to be affected. © 2012 Pearson Education, Inc.

139. 9.22 CONNECTION: Human sex-linked disorders affect mostly males  Recessive and sex-linked human disorders include –hemophilia, characterized by excessive bleeding because hemophiliacs lack one or more of the proteins required for blood clotting, –red-green color blindness, a malfunction of light- sensitive cells in the eyes, and –Duchenne muscular dystrophy, a condition characterized by a progressive weakening of the muscles and loss of coordination. © 2012 Pearson Education, Inc.

140. Figure 9.22 Female Male Hemophilia Carrier Normal Alexis Alexandra Czar Nicholas II of Russia Queen Victoria Alice Louis Albert

141. Figure 9.22_1

142. 9.23 EVOLUTION CONNECTION: The Y chromosome provides clues about human male evolution  The Y chromosome provides clues about human male evolution because –Y chromosomes are passed intact from father to son and –mutations in Y chromosomes can reveal data about recent shared ancestry. © 2012 Pearson Education, Inc.

143. Figure 9.23

144. 1.Describe pangenesis theory and the blending hypothesis. Explain why both ideas are now rejected. 2.Define and distinguish between true-breeding organisms, hybrids, the P generation, the F 1 generation, and the F 2 generation. 3.Define and distinguish between the following pairs of terms: homozygous and heterozygous; dominant allele and recessive allele; genotype and phenotype. Also, define a monohybrid cross and a Punnett square. You should now be able to © 2012 Pearson Education, Inc.

145. 4.Explain how Mendel’s law of segregation describes the inheritance of a single characteristic. 5.Describe the genetic relationships between homologous chromosomes. 6.Explain how Mendel’s law of independent assortment applies to a dihybrid cross. 7.Explain how and when the rule of multiplication and the rule of addition can be used to determine the probability of an event. You should now be able to © 2012 Pearson Education, Inc.

146. 8.Explain how family pedigrees can help determine the inheritance of many human traits. 9.Explain how recessive and dominant disorders are inherited. Provide examples of each. 10.Compare the health risks, advantages, and disadvantages of the following forms of fetal testing: amniocentesis, chorionic villus sampling, and ultrasound imaging. You should now be able to © 2012 Pearson Education, Inc.

147. 11.Describe the inheritance patterns of incomplete dominance, multiple alleles, codominance, pleiotropy, and polygenic inheritance. 12.Explain how the sickle-cell allele can be adaptive. 13.Explain why human skin coloration is not sufficiently explained by polygenic inheritance. 14.Define the chromosome theory of inheritance. Explain the chromosomal basis of the laws of segregation and independent assortment. You should now be able to © 2012 Pearson Education, Inc.

148. 15.Explain how linked genes are inherited differently from nonlinked genes. 16.Describe T. H. Morgan’s studies of crossing over in fruit flies. Explain how Sturtevant created linkage maps. 17.Explain how sex is genetically determined in humans and the significance of the SRY gene. 18.Describe patterns of sex-linked inheritance and examples of sex-linked disorders. 19.Explain how the Y chromosome can be used to trace human ancestry. You should now be able to © 2012 Pearson Education, Inc.

149. Figure 9.UN01 Fertilization Meiosis Homologous chromosomes Alleles, residing at the same locus Paired alleles, different forms of a gene Haploid gametes (allele pairs separated) Gamete from the other parent Diploid zygote (containing paired alleles)

150. Figure 9.UN02 Incomplete dominance Red RR White rr Pink Rr

151. Figure 9.UN03 Single gene Pleiotropy Multiple characters

152. Figure 9.UN04 Multiple genes Polygenic inheritance Single characters (such as skin color)

153. Figure 9.UN05 chromosomes Genes heterozygous located on alternative versions called at specific locations called if both are the same, the genotype is called if different, the genotype is called the expressed allele is called the unexpressed allele is called inheritance when the phenotype is in between is called (a) (b)(c) (d)(e) (f)

154. Figure 9.UN06