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Observable Patterns of Inheritance. Can you do this?

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Presentation on theme: "Observable Patterns of Inheritance. Can you do this?"— Presentation transcript:

1 Observable Patterns of Inheritance

2 Can you do this?

3 Terms to Know Probability Probability True-breeding True-breeding Hybrid Hybrid Segregation Segregation Traits Traits Genes Genes Homozygous Heterozygous Phenotype Genotype Dominant Recessive

4 Genes Chemical factors that determine traits (units of information) Chemical factors that determine traits (units of information) Analogy: Genes are like a combination of ingredients in a recipe. They code for a specific food. Analogy: Genes are like a combination of ingredients in a recipe. They code for a specific food. Passed from parents to offspring Passed from parents to offspring Each has a specific location (locus) on a chromosome Each has a specific location (locus) on a chromosome

5 Alleles Different forms of a gene (back to analogy…replacing jiffy p.b. with skippy p.b.) Different forms of a gene (back to analogy…replacing jiffy p.b. with skippy p.b.) Dominant allele (Uppercase letter) overrules a recessive allele (lowercase letter) that it is paired with Dominant allele (Uppercase letter) overrules a recessive allele (lowercase letter) that it is paired with

6 Allele Combinations Homozygous =purebred Homozygous =purebred having two identical alleles at a locus having two identical alleles at a locus AA (dominant expressed) or aa (recessive expressed) AA (dominant expressed) or aa (recessive expressed) Heterozygous =hybrid Heterozygous =hybrid having two different alleles at a locus having two different alleles at a locus Aa (dominant expressed) Aa (dominant expressed)

7 Genotype & Phenotype Genotype refers to particular genes an individual carries Genotype refers to particular genes an individual carries Phenotype refers to an individuals observable traits Phenotype refers to an individuals observable traits Cannot always determine genotype by observing phenotype Cannot always determine genotype by observing phenotype

8 Tracking Generations Parental generation P Parental generation P mates to produce First-generation offspring F 1 First-generation offspring F 1 mate to produce Second-generation offspring F 2 Second-generation offspring F 2

9 Earlobe Variation Whether a person is born with attached or detached earlobes depends on a single gene Whether a person is born with attached or detached earlobes depends on a single gene Gene has two molecular forms (alleles) Gene has two molecular forms (alleles)

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11 Earlobe Variation Earlobe Variation You inherited one allele for this gene from each parent You inherited one allele for this gene from each parent Dominant allele specifies detached earlobes (E) Dominant allele specifies detached earlobes (E) Recessive allele specifies attached earlobes (e) Recessive allele specifies attached earlobes (e)

12 Dominant & Recessive Alleles If you have attached earlobes, you inherited two copies of the recessive allele If you have attached earlobes, you inherited two copies of the recessive allele If you have detached earlobes, you may have either one or two copies of the dominant allele If you have detached earlobes, you may have either one or two copies of the dominant allele

13 Early Ideas About Heredity People knew that sperm and eggs transmitted information about traits People knew that sperm and eggs transmitted information about traits Blending theory Blending theory Problem: Problem: Would expect variation to disappear Would expect variation to disappear Variation in traits persists Variation in traits persists

14 Gregor Mendel Gregor Mendel Strong background in plant breeding and mathematics Strong background in plant breeding and mathematics Using pea plants, found indirect but observable evidence of how parents transmit genes to offspring Using pea plants, found indirect but observable evidence of how parents transmit genes to offspring

15 Mendel was born in1822 Mendel was born in1822 Austrian monk Austrian monk Studied at the Univ. of Vienna Studied at the Univ. of Vienna Teacher (High School) Teacher (High School)

16 Filament Anther Stigma Style Ovary Carpel Petal Sepal Ovule Stamen Section 24-1 Figure 24–5 The Structure of a Flower

17 The Garden Pea Plant Self-pollinating Self-pollinating True breeding (different alleles not normally introduced) True breeding (different alleles not normally introduced) Can be experimentally cross- pollinated Can be experimentally cross- pollinated

18 How did Mendel fertilize the plants?

19 F 1 Results of One Monohybrid Cross F 1 Results of One Monohybrid Cross

20 FM Dominant trait is expressed Recessive appears

21 Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall Figure 11-3 Mendels Seven F 1 Crosses on Pea Plants

22 F 1 Results of Mendels Dihybrid Crosses F 1 Results of Mendels Dihybrid Crosses All plants displayed the dominant form of both traits All plants displayed the dominant form of both traits We now know: We now know: All plants inherited one allele for each trait from each parent All plants inherited one allele for each trait from each parent All plants were heterozygous (AaBb) All plants were heterozygous (AaBb)

23 Principle of Dominance Some alleles are dominant and others are recessive. Some alleles are dominant and others are recessive.

24 Mendel wanted to know if the recessive alleles disappeared or are they still in the f1,just hidden. Mendel wanted to know if the recessive alleles disappeared or are they still in the f1,just hidden.

25 P Generation F 1 Generation F 2 Generation TallShortTall Short Principles of Dominance

26 P Generation F 1 Generation F 2 Generation TallShortTall Short Principles of Dominance

27 P Generation F 1 Generation F 2 Generation TallShortTall Short Principles of Dominance

28 Mendels Theory of Segregation Mendels Theory of Segregation An individual inherits a unit of information (allele) about a trait from each parent An individual inherits a unit of information (allele) about a trait from each parent During gamete formation, the alleles segregate from each other During gamete formation, the alleles segregate from each other

29 Independent Assortment Mendel concluded that the two units for the first trait were to be assorted into gametes independently of the two units for the other trait Mendel concluded that the two units for the first trait were to be assorted into gametes independently of the two units for the other trait Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis

30 Independent Assortment Metaphase I Metaphase II: Gametes: 1/4 AB1/4 ab1/4 Ab1/4 aB AAAA AAAA AAAA BB BB BB BB BBBB aaaa aaaa aaaa bbbb bbbb bbbb OR

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32 F 2 Results of Monohybrid Cross

33 Type of alleles The physical characteristic

34 Impact of Mendels Work Mendel presented his results in 1865 Mendel presented his results in 1865 Paper received little notice Paper received little notice Mendel discontinued his experiments in 1871 Mendel discontinued his experiments in 1871 Paper rediscovered in 1900 and finally appreciated Paper rediscovered in 1900 and finally appreciated

35 Probability The likelihood that a particular event will occur. The likelihood that a particular event will occur. Flip a coin. Flip a coin. We use Punnett Squares We use Punnett Squares

36 D 38- Deduce the probable mode of inheritance of traits (e.g., D 38- Deduce the probable mode of inheritance of traits (e.g.,

37 Punnett Squares of Test Crosses Homozygous recessive a A aaa Aa aa Homozygous recessive a A AAa Two phenotypesAll dominant phenotype

38 Punnett Square of a Monohybrid Cross Female gametes Male gametes A a A a AAAa aa Dominant phenotype can arise 3 ways, recessive only one

39 Test Cross Individual that shows dominant phenotype is crossed with individual with recessive phenotype Individual that shows dominant phenotype is crossed with individual with recessive phenotype Examining offspring allows you to determine the genotype of the dominant individual Examining offspring allows you to determine the genotype of the dominant individual

40 Tt X Tt Cross

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43 Genetics Practice Problem 1 What occurs when a purple plant that is heterozygous is fertilized by a white plant? What occurs when a purple plant that is heterozygous is fertilized by a white plant? Identify generations Identify generations Punnett Square Punnett Square Genotypes % Genotypes % Phenotype % Phenotype %

44 Principle of Independent Assortment The genes for different traits separate independently of one another during the formation of gametes. The genes for different traits separate independently of one another during the formation of gametes.

45 Figure Independent Assortment in Peas

46 Yellow round 9/16 Yellow round 9/16 Green round 3/16 Green round 3/16 Yellow wrinkled 3/16 Yellow wrinkled 3/16 Green wrinkled 1/16 Green wrinkled 1/16 9 : 3 : 3 : 1 Ratio 9 : 3 : 3 : 1 Ratio

47 Dihybrid Cross Experimental cross between individuals that are homozygous for different versions of two traits

48 Straight Thumb (Dominant) Curved Thumb (Recessive) Straight Pinky (Dominant) Bent Pinky (Recessive)

49 More Dominant Traits Polydactylism Achondroplastic Dwarfism Tay-Sachs Disease - One Wrong Letter

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51 Dominance Relations Complete dominance Complete dominance Incomplete dominance Incomplete dominance Heterozygote phenotype is somewhere between that of two homozyotes Heterozygote phenotype is somewhere between that of two homozyotes Codominance Codominance Non-identical alleles specify two phenotypes that are both expressed in heterozygotes Non-identical alleles specify two phenotypes that are both expressed in heterozygotes

52 Flower Color in Snapdragons: Incomplete Dominance Flower Color in Snapdragons: Incomplete Dominance Red-flowered plant X White-flowered plant Pink-flowered F 1 plants (homozygote) (heterozygotes)

53 Flower Color in Snapdragons: Incomplete Dominance Red flowers - two alleles allow them to make a red pigment Red flowers - two alleles allow them to make a red pigment White flowers - two mutant alleles; cant make red pigment White flowers - two mutant alleles; cant make red pigment Pink flowers have one normal and one mutant allele; make a smaller amount of red pigment Pink flowers have one normal and one mutant allele; make a smaller amount of red pigment

54 Figure Incomplete Dominance in Four OClock Flowers

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56 Flower Color in Snapdragons: Incomplete Dominance Pink-flowered plant X Pink-flowered plant White-, pink-, and red-flowered plants White-, pink-, and red-flowered plants in a 1:2:1 ratio (heterozygote)

57 Incomplete Dominance Neither allele is dominant over the other Combination of red and white flowers

58 Codominant Sickle Cell Disease Sickle Cell Disease ABO Blood Types ABO Blood Types

59 Pleitropy Alleles at a single locus may have effects on two or more traits Alleles at a single locus may have effects on two or more traits Classic example is the effects of the mutant allele at the beta-globin locus that gives rise to sickle-cell anemia Classic example is the effects of the mutant allele at the beta-globin locus that gives rise to sickle-cell anemia

60 Teachers Domain - A Mutation Story

61 Genetics of Sickle-Cell Anemia Genetics of Sickle-Cell Anemia Two alleles Two alleles 1) Hb A Encodes normal beta hemoglobin chain 2) Hb S Mutant allele encodes defective chain Hb S homozygotes produce only the defective hemoglobin; suffer from sickle- cell anemia Hb S homozygotes produce only the defective hemoglobin; suffer from sickle- cell anemia

62 Pleiotrophic Effects of Hb S /Hb S At low oxygen levels, cells with only Hb S hemoglobin sickle and stick together At low oxygen levels, cells with only Hb S hemoglobin sickle and stick together This impedes oxygen delivery and blood flow This impedes oxygen delivery and blood flow Over time, it causes damage throughout the body Over time, it causes damage throughout the body

63 Blood Typing Karl Landsteiner 1897 Karl Landsteiner 1897 Worked at the Univ. of Vienna, Vienna Austria (Sound familiar?) Worked at the Univ. of Vienna, Vienna Austria (Sound familiar?) Wanted to find out which red blood cells would clot Wanted to find out which red blood cells would clot

64 First found two different groups, A and B First found two different groups, A and B Third group would not clot when exposed to A or B What do you think this was? Third group would not clot when exposed to A or B What do you think this was? What about the forth group? What about the forth group?

65 Genetics of ABO Blood Types: Three Alleles Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells Two alleles (I A and I B ) are codominant when paired Two alleles (I A and I B ) are codominant when paired Third allele (i) is recessive to others Third allele (i) is recessive to others

66 ABO Blood Type: Glycolipids on Red Cells Type A - Glycolipid A on cell surface Type A - Glycolipid A on cell surface Type B - Glycolipid B on cell surface Type B - Glycolipid B on cell surface Type AB - Both glyocolipids A & B Type AB - Both glyocolipids A & B Type O - Neither glyocolipid A nor B Type O - Neither glyocolipid A nor B

67 ABO Blood Type: Allele Combinations Type A - I A I A or I A i Type A - I A I A or I A i Type B - I B I B or I B i Type B - I B I B or I B i Type AB - I A I B Type AB - I A I B Type O - ii Type O - ii

68 ABO and Transfusions Recipients immune system will attack blood cells that have an unfamiliar glycolipid on surface Recipients immune system will attack blood cells that have an unfamiliar glycolipid on surface Type O is universal donor because it has neither type A nor type B glycolipid Type O is universal donor because it has neither type A nor type B glycolipid

69 Codominance and Multiple Alleles - AB or NOT AB Codominance - both alleles are dominant I A and I B Multiple Alleles - genes have more than two alleles I A, I B, I a

70 Phenotype (Blood Type Genotype Antigen on Red Blood Cell Safe Transfusions To From Figure 14-4 Blood Groups

71 Universal Acceptor Universal Donor

72 Rh factor - Another Blood Trait Pregnancy complications Pregnancy complications Rh is a type of protein in the blood Rh is a type of protein in the blood If an Rh- man reproduces with an Rh + woman complications can occur. If an Rh- man reproduces with an Rh + woman complications can occur.

73 Polygenic Traits: Desirees Baby Case Study More than one gene controls a trait More than one gene controls a trait Skin color more than one gene, incomplete dominance Skin color more than one gene, incomplete dominance

74 A,B and C are darka,b and c are light

75 Sex Linked Traits - traits that are carried on the either the x or y chromosome

76 Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Male Female Figure Colorblindness

77 Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Male Female Figure Colorblindness

78 Colorblindness

79 Cystic Fibrosis - Finding Cures is Hard Sex-Linked Disorder

80 Male Pattern Baldness (X chromosome) Hairy Pinna - long hair on ears

81 Chromosome # 7 CFTR gene The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein. Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane. The cells in the persons airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus. Figure 14-8 The Cause of Cystic Fibrosis Recessive Disorder

82 Albinism Phenotype results when pathway for melanin production is completely blocked Phenotype results when pathway for melanin production is completely blocked Genotype - Homozygous recessive at the gene locus that codes for tyrosinase, an enzyme in the melanin-synthesizing pathway Genotype - Homozygous recessive at the gene locus that codes for tyrosinase, an enzyme in the melanin-synthesizing pathway

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86 Human Genetics

87 Tracing Genes Through Families - Human Pedigrees Female Male Partner Brothers and Sisters

88 A circle represents a female. A square represents a male. A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A half-shaded circle or square indicates that a person is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait. Figure 14-3 A Pedigree

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90 Ability to roll the tongue in the Senator Family Tongue Roller - dominant, Non-Tongue Roller - recessive White = tongue roller, Purple = non-roller What are the genotypes of everyone? R = roller, r = non roller

91 George, Sam, Ann, Michael, Daniel and Alan are Rr Arlene, Tom, Wilma, and Carla are rr Sandra, Tina and Christopher are either RR or Rr

92 Case Study - Hemophilia and the Royal Family

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94 1. First, lets take a look at Queen Victorias son Leopolds family. His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other childrena boy and a girlwhose status is unknown. a) What is the probability that her other son was hemophilic? b) What is the probability that her daughter was a carrier? Hemophilic? c) What is the probability that both children were normal?

95 2. Now for the Spanish connection: Victorias youngest child, Beatrice, gave birth to one daughter, one normal son, and two hemophilic sons. Looking at the pedigree of the royal family, identify which of Beatrices children received the hemophilic gene; why can you make this conclusion? Notice that Beatrices daughter, Eugenie, married King Alfonso XIII of Spain and had six children, one of whom was the father of Juan Carlos, the current King of Spain. Would you predict that Juan Carlos was normal, a carrier, or a hemophilic?

96 3. Alexis did not die from hemophilia. At the age of fourteen he was executed with the rest of the family. His four oldest sisters were also young and didnt have children, so we dont know whether any of them was a carrier. But we can make an estimate. a) What are the probabilities that all four of the girls were carriers of the allele hemophilia? b) Supposing Alexis had lived and married a normal woman, what are the chances that his daughter would be a hemophiliac? c) What are the chances his daughters would be carriers? d) What are the chances that his sons would be hemophiliacs?

97 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Nondisjunction

98 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Nondisjunction

99 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Nondisjunction

100 Epistasis Interaction between the products of gene pairs Interaction between the products of gene pairs Common among genes for hair color in mammals Common among genes for hair color in mammals

101 Genetics of Coat Color in Labrador Retrievers Genetics of Coat Color in Labrador Retrievers Two genes involved Two genes involved - One gene influences melanin production Two alleles - B (black) is dominant over b (brown) Two alleles - B (black) is dominant over b (brown) - Other gene influences melanin deposition Two alleles - E promotes pigment deposition and is dominant over e Two alleles - E promotes pigment deposition and is dominant over e

102 Allele Combinations and Coat Color Black coat - Must have at least one dominant allele at both loci Black coat - Must have at least one dominant allele at both loci BBEE, BbEe, BBEe, or BbEE BBEE, BbEe, BBEe, or BbEE Brown coat - bbEE, bbEe Brown coat - bbEE, bbEe Yellow coat - Bbee, BbEE, bbee Yellow coat - Bbee, BbEE, bbee

103 Comb Shape in Poultry Alleles at two loci (R and P) interact Walnut comb - RRPP, RRPp, RrPP, RrPp Walnut comb - RRPP, RRPp, RrPP, RrPp Rose comb - RRpp, Rrpp Rose comb - RRpp, Rrpp Pea comb - rrPP, rrPp Pea comb - rrPP, rrPp Single comb - rrpp Single comb - rrpp

104 Campodactyly: Unexpected Phenotypes Effect of allele varies: Effect of allele varies: Bent fingers on both hands Bent fingers on both hands Bent fingers on one hand Bent fingers on one hand No effect No effect Many factors affect gene expression Many factors affect gene expression

105 Continuous Variation Continuous Variation A more or less continuous range of small differences in a given trait among individuals A more or less continuous range of small differences in a given trait among individuals The greater the number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait The greater the number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait

106 Human Variation Some human traits occur as a few discrete types Some human traits occur as a few discrete types Attached or detached earlobes Attached or detached earlobes Many genetic disorders Many genetic disorders Other traits show continuous variation Other traits show continuous variation Height Height Weight Weight Eye color Eye color

107 Temperature Effects on Phenotype Himalayan rabbits are Homozygous for an allele that specifies a heat- sensitive version of an enzyme in melanin- producing pathway Himalayan rabbits are Homozygous for an allele that specifies a heat- sensitive version of an enzyme in melanin- producing pathway Melanin is produced in cooler areas of body Melanin is produced in cooler areas of body

108 Environmental Effects on Plant Phenotype Environmental Effects on Plant Phenotype Hydrangea macrophylla Hydrangea macrophylla Action of gene responsible for floral color is influenced by soil acidity Action of gene responsible for floral color is influenced by soil acidity Flower color ranges from pink to blue Flower color ranges from pink to blue


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