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Nutritional Sciences: From Fundamentals to Food
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Chapter C5SC / Exercise 9
Nutritional Sciences: From Fundamentals to Food
McGuire
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Unformatted text preview: 1 TUESDAY, OCT 27 2 New practice on Mastering … 3 Ch 9: Inheritance & Mendel 4 Introduction § 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 – behavioral traits 5 Figure 9.0_2 6 Figure 9.0-2 7 Pangenesis was an early explanation for inheritance – It was proposed by Hippocrates – Particles called pangenes came from all parts of the organism to be incorporated into eggs or sperm – 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 8 Blending was another idea, based on plant breeding Hereditary material from parents mixes together to form an intermediate trait, like mixing paint 9 Heredity vs. Genetics § Heredity § transmission of traits from one generation to the next § Genetics § scientific study of heredity 10 Gregor Mendel – began the field of genetics in the 1860s – deduced the principles of genetics by breeding garden peas – relied upon a background of mathematics, physics, and chemistry 11 Mendel and His Peas 1 § Genetics § scientific study of heredity 10 Gregor Mendel – began the field of genetics in the 1860s – deduced the principles of genetics by breeding garden peas – relied upon a background of mathematics, physics, and chemistry 11 Mendel and His Peas •  Research in Czech Republic – Mendel worked in the period from 1856–1863, observing generations of pea plants and applying mathematics to create a set of principles to govern inheritance – Without ever knowing what genes were, he figured out how they worked 12 Mendel and His Peas •  In 1866, Mendel correctly argued that parents pass on to their offspring discrete “heritable factors” •  He stressed that the heritable factors (today called genes) retain their individuality generation after generation 13 Mendel and His Peas •  Basic ideas – Basic units of genetics -- material elements that come in pairs – Elements do not change (even over many generations) – Pairs separate during the formation of gametes 14 Mendel and His Peas •  A heritable feature that varies among individuals (e.g. flower color) = a character •  Each variant for a character (e.g. purple or white flowers) = a trait 15 •  Anatomy – Simple – Macroscopic – Easily described 2 15 15 15 16 16 17 16 18 17 19 17 18 18 19 19 20 21 20 21 20 21 22 22 22 23 23 23 color) = a character A heritable feature that varies among individuals flower •  Each variant for a character (e.g. purple or white (e.g. flowers) =a trait color) = a character •  Each variant for a character (e.g. purple or white flowers) = a trait •  Each variant for a character (e.g. purple or white flowers) = a trait •  Anatomy – Simple •  Anatomy – Macroscopic – Simple •  Anatomy – Easily described – Macroscopic – Simple Mendel’s Experimental Model: – Easily described –  M acroscopic Pisum sativum Mendel’s Experimental Model: – Easily described Figure 9.2c-3 Pisum sativum Mendel’s Experimental Model: Pisum sativum Figure 9.2d-0 9.2c-3 9.2c-3 Phenotype and Genotype Figure 9.2d-0 • Figure Phenotype 9.2d-0 Phenotype and Genotype – physical function, bodily characteristic, or action • Phenotype Phenotypeand Genotype – physical function, bodily characteristic, or action •  Phenotype Genotype pnderlying hysical function, bodily characteristic, or action – u genes that determine the phenotype •  Genotype Figure 9.2d-1 genes that determine the phenotype – underlying •  Genotype Mendel and His Peas Figure 9.2d-1 – underlying genes that determine the phenotype Figure 9.2d-1 Mendel and His Peas •  True-breeding varieties = self-fertilization produces offspring Mendel and His Peas all identical to the parent •  True-breeding varieties = self-fertilization produces offspring all identical to the parent •  The offspring ofvarieties two different varieties areproduces hybrids offspring True-breeding = self-fertilization all identical to the parent •  The offspring of two different varieties are hybrids •  Cross-fertilization = hybridization, or genetic cross •  The offspring of two different varieties are hybrids Mendel and His Peas •  Cross-fertilization = hybridization, or genetic cross Mendel and His Peas •  Cross-fertilization = hybridization, or genetic cross •  True-breeding parental plants = P generation Mendel and His Peas •  True-breeding parental plants = P generation •  Hybrid offspring = F1 generation •  True-breeding parental plants = P generation •  Hybrid offspring = F1 generation •  A cross of F1 plants produces an F2 generation •  Hybrid offspring = F1 generation •  A cross of F1 plants produces an F2 generation Example of a monohybrid cross •  A cross of F1 plants produces an F2 generation Example of a monohybrid cross Example of a monohybrid cross § Parental (P) generation: purple flowers x white flowers § 1st filial (F1) generation: § Parental (P) generation: purple flowers x white flowers § all plants with purple flowers st 3 nd filialoffspring • § 2 Hybrid (F2) generation: = F1 generation § # of plants with purple flowers •  A§ #cross of plants of F1with plants white produces flowersan F2 generation 24 23 25 Figure 9.3a-3 Example of a monohybrid cross § Mendel needed to explain – Why one trait seemed to disappear in the F1 generation 26 24 25 27 28 26 27 29 28 30 31 § Parental (P) generation: purple flowers x white flowers – Why that trait reappeared in ¼ of the F2 offspring § 1st filial (F1) generation: § all plants with purple flowers Monohybrid & § 2nd filial (F2) Crosses generation: Segregation Alleles § # of plantsof with purple flowers •  Setting up Crosses § # of plants with white flowers – Start: true-breeding stocks (gave only similar offspring) Figure 9.3a-3 – Took pollen from one variety and placed it on the stigma of the other variety P generation to produce the F1 § Mendel needed to = explain – generation Why one trait seemed to disappear in the F1 generation – Why9.3A_s3 that trait reappeared in ¼ of the F2 offspring Figure Looking at seeds (peas) Monohybrid Crosses & •  Setting up Crosses Segregation of Alleles – Offspring = F1 (1st filial) •  Setting up Crosses • Expected: mix of traits – S• tart: true-breeding stocks (gave only similar offspring) Result: all yellow (= dominant) • To determine where green went, Mendel self-pollinated – Took pollen from one variety and placed it on the stigma of these F1 plants the other variety = P generation to produce the F1 generation – Next generation of offspring = F2 (2nd filial) • 6,022 yellow and 2,001 green Figure 9.3A_s3 • Green came back, but only as a specific proportion --- 3:1 Looking at seeds (peas) • WHERE Setting IS up THE Crosses GENETIC VARIABILITY COMING FROM? – Offspring = F1 (1st filial) Thought Question • Expected: mix of traits The • figure diagrams one the genetic crosses that helped Result: all yellow (= of dominant) Mendel his theories inheritance. Whichself-pollinated process • To form determine where of green went, Mendel distributes these P F1alleles plantsto approximately one half of the F1 gametes and the p allele to the other half? – Next generation of offspring = F2 (2nd filial) a) fertilization • 6,022 yellow and 2,001 green b) mitosis • Green came back, but only as a specific proportion --- 3:1 c) meiosis 4 29 30 WHERE IS THE GENETIC VARIABILITY COMING FROM? 31 Thought Question The figure diagrams one of the genetic crosses that helped Mendel form his theories of inheritance. Which process distributes P alleles to approximately one half of the F1 gametes and the p allele to the other half? a) fertilization b) mitosis c) meiosis d) chromosome crossover 32 Think about your answer .. •  Why did you choose your answer? •  Did the person next to you choose the same answer? •  If yes, what about on your other side? Behind you? In front of you? •  Can you convince them that you are right? Or can they convince you that they are? 33 Answer The figure diagrams one of the genetic crosses that helped Mendel form his theories of inheritance. Which process distributes P alleles to approximately one half of the F1 gametes and the p allele to the other half? c) meiosis 34 Mendel’s Results •  Interpreting the Results – Unlike his predecessors, Mendel carefully counted and interpreted the numbers – Found that varieties did not blend • One is dominant (shows up) • Other recessive (is masked by the dominant) • These varieties of genes are called alleles 35 36 Yellow & Green Peas •  Interpreting the Results – F3 (3rd filial) generation • From the yellow F2 5 interpreted the numbers – Julianna is 5 years old. Should her parents have let her – know Foundhow thatgrave varieties not blend her did situation is? Should they have asked •  O ne is dominant (shows up) her about her end-of-life wishes? And now that those • Other are recessive masked the dominant) wishes known,(is should herby parents heed them? 57 35 “Heaven over Hospital” • These varieties of genes are called alleles Michelle: Julianna, if you get sick again, do you want to go to the hospital again or stay home? 36 Yellow & Green Peas Not the the Results hospital • Julianna: Interpreting – F3 (3rd filial) generation Michelle: if that means that you will go to heaven if you • FromEven the yellow F2 stay home? – 2/3 gave mixtures of green and yellow (not pure yellow parents) Julianna: hate NT. in I hate hospital. – 1/3Yes... were Iall yellow the Fthe 3 (pure yellow) • From the green F2 Michelle: Right. So if you get sick again, you want to stay – 100 % green home. But you know that probably means you will go to heaven, right? •  Things to think about … – Homozygous vs. heterozygous Julianna: (nods) – How to use a Punnett square 37 Michelle: And it probably means that you will go to heaven by yourself, and Mommy will join you later. 38 39 Julianna: But I won't be alone. 40 58 41 59 42 60 43 61 LET’S TAKEMendel? A BREAK … Remember • Rules I mentioned theClub!! idea that Mendel wrote four laws governing of Break inheritance … •  Worksheet – pick up one per PAIR of students. No more than Segregation of Alleles two people working together – and I must see TWO different the sheet! Thanks! •  handwritings Mendel’s Firston Law The must completed today! – P ea worksheet cells contain twobe copies of each gene (alleles) – Alleles do not blend •  Pick up copy, examsdominant, … when Dr.C. poststhe theexpression first letter of • one can mask of your the last name on the screen recessive copy but the worksheet is your priority! – Alleles must separate Rules of Break Club!! during meiosis Mnumbers endel didn’t know this!! •  It’s• a game!! – One of me --- 200+ of you! Mendel developed four hypotheses •  Question priority 1. Alleles versions of genes that – 5 fingersare up alternative = we are sinking! for=variations in inherited characters. – 3account fingers up we can make it, but we have a question – 1 finger up (not the middle one!) = I gotta random thought that you’ll but it can wait until inherits later two 2. For each love, character, an organism 6 67 – Alleles do not blend ne copy,square dominant, can mask expression of the of – A• oPunnett shows the four the possible combinations recessive copy occur when these gametes combine. alleles that could – Alleles must separate during meiosis • Mendel didn’t know this!! Figure 9.3b-0-3 61 68 Mendel9.3b-1 developed four hypotheses Figure 66 69 70 71 62 1. Alleles are alternative versions of genes that account for variations in inherited characters. 2. For each character, an organism inherits two § Foralleles, a pair of homologous alleles gene one from each chromosomes, parent. The alleles canofbea the reside at or thedifferent. same locus same – H• omozygous individuals have same allele on both A homozygous genotype hasthe identical alleles. homologues • A heterozygous genotype has two different alleles. – Heterozygous individuals have a different allele on each Figure 9.4 homologue 63 72 73 74 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 BUT WAIT! and is called the recessive allele. •  What happens when you cross F1 generations? – The phenotype the that appearance or present expression of a trait. •  Mendel observes is traits were NOT in the – The genotype is the genetic makeup of a trait. parents!! – In a 9:3:3:1 phenotypic ratio – NOTE!! same phenotype may be determined by more •  HOW CANThe THAT BE?! than one genotype. WHY?? 75 64 76 4. A sperm or egg carries only one allele for each inherited § Mendel needed to explain character because allele pairs separate (segregate) from each other during the production were of gametes. This • Why nonparental combinations observed in statement later isgenerations called the law of segregation. • Why a 9:3:3:1 ratio wasatobserved among the allele F2 offspring – The fusion of gametes fertilization creates pairs if he considered once again. more than a single trait (remember homologous chromosomes!!??!) 77 65 78 79 What do his laws have to do with traits? We need tohypotheses look at two explained traits to have better of •  Mendel’s the a3:1 ratiounderstanding in the F2 generation. what really goes on … – The F1 hybrids all have a Pp genotype. Mendel’s Dihybrid (2 traits) Cross § Parental generation: – A Punnett square shows the four possible combinations of round yellow seedsoccur x wrinkled seeds combine. alleles that could when green these gametes 7 • Why a 9:3:3:1 ratio was observed among the F2 offspring if he considered more than a single trait 77 What do his laws have to do with traits? We need to look at two traits to have a better understanding of what really goes on … 78 79 Mendel’s Dihybrid (2 traits) Cross § Parental generation: round yellow seeds x wrinkled green seeds § F1 generation: § all plants with round yellow seeds § F2 generation: § # of plants with round yellow § # of plants with round green § # of plants with wrinkled yellow § # of plants with wrinkled green seeds 80 Dihybrid Crosses •  Example: Yellow (Y)/green (y) and smooth (S)/wrinkled (s) – F1: • all yellow and smooth (self-pollinated) – F2: • 9 yellow and smooth • 3 yellow and wrinkled • 3 green and smooth • 1 green and wrinkled 81 82 Figure 9.5a-3 83 Law of Independent Assortment •  During gamete formation, gene pairs assort independently •  Due to random nature of how tetrads line up (metaphase I of meiosis) 84 Figure 9.5b-0 85 TUESDAY, NOV 3 86 New practice on Mastering … 87 Testcross 8 83 85 86 84 87 85 86 84 87 85 86 87 88 89 88 89 88 89 90 91 90 91 90 92 91 93 94 92 95 93 96 94 92 95 93 96 94 95 Law Assortment •  DueoftoIndependent random nature of how tetrads line up (metaphase I of TUESDAY, NOV 3 •  meiosis) During gamete formation, gene pairs assort independently New practice on Mastering … • Testcross Due to9.5b-0 random nature of how tetrads line up (metaphase I of Figure meiosis) § What is it?NOV 3 TUESDAY, New practice on Mastering … of unknown genotype and a Figure 9.5b-0 – Mating between an individual homozygous individual (i.e. dd) Testcross TUESDAY, NOVrecessive 3 – Will show whether the unknown genotype includes a § What is it? on Mastering … New practice recessive allele – Used by Mendel to confirm true-breeding genotypes Testcross – Mating between an individual of unknown genotype and a Figure 9.6it? homozygous recessive individual (i.e. dd) § What is – Will show whether the unknown genotype includes a Evo Connection allele an individual of unknown genotype and a – recessive Mating between § In a simple dominant-recessive inheritance of dominant allele recessive individual (i.e. dd) genotypes – homozygous Used by Mendel to confirm true-breeding A and recessive allele a – Will 9.6 show whether the unknown genotype includes a Figure •  a recessive phenotype always results from a homozygous recessive allele recessive genotype (aa) Evo – UConnection sed by Mendel to confirm true-breeding genotypes § In a simple inheritance of dominant allele Figure 9.6 dominant-recessive •  a dominant phenotype can result from either A and recessive allele a – homozygous dominant genotype (AA) Evo •  aConnection recessive phenotype always results from a homozygous – heterozygous genotype genotype (aa) (Aa) § In recessive a simple dominant-recessive inheritance of dominant allele A and recessive allele a § W traitsphenotype (those prevailing in nature) recessive phenotype always results •  ild-type a dominant can result from from eithera homozygous § nrecessive ot necessarily specified by dominant alleles! genotype (aa) genotype (AA) – homozygous dominant – heterozygous genotype (Aa) •  a dominant phenotype can result from either Pedigree – homozygous dominant genotype (AA) § Wild-type traits (those prevailing in nature) •  Shows the inheritance of a trait in a family through multiple – heterozygous genotype § not necessarily specified by(Aa) dominant alleles! generations •  Demonstrates dominant or recessive inheritance § Wild-type traits (those prevailing in nature) • Pedigree Can also be used to deduce genotypes of family members § not necessarily specified by dominant alleles! •  Shows the inheritance of a trait in a family through multiple generations Figure 9.8B • Pedigree Demonstrates dominant or recessive inheritance Figure 9.8-2 Shows thebeinheritance of a trait in a family through multiple •  Can also used to deduce genotypes of family members generations Figure 9.8-3 •  Demonstrates dominant or recessive inheritance Figure 9.8B 9.8-4 •  Can also be used to deduce genotypes of family members Figure 9.8-2 Inherited disorders in humans § Inherited human disorders show either Figure 9.8-3 9.8B 9.8-2 inheritance Figure 9.8-4 1. recessive – two recessive in alleles are needed to show disease Figure 9.8-3 Inherited disorders humans – heterozygous parentsshow are carriers of the disease§  I nherited human disorders either Figurecausing 9.8-4 allele 9 93 § Inherited human disorders show either Figure 9.8-2 99 Figure 9.8-3 inheritance 1. recessive – two recessive alleles are needed to show disease Figure 9.8-4 – heterozygous parents are carriers of the diseaseInherited disorders causing allele in humans § Inherited humanofdisorders show either with inbreeding, – probability inheritance increases mating between close relatives 2.  ominant inheritance 1. d recessive inheritance – one dominant alleles allele isare needed to show disease – two recessive needed to show disease – dominant lethal allelesare arecarriers usually of eliminated from the – heterozygous parents the diseasepopulation causing allele of inheritance increases with inbreeding, Table– probability 9.9 mating between close relatives NOTE CARD inheritance 2. dominant Fill out yourdominant note cardallele as indicated here. Answer the questions – one is needed to show disease on your own, please. – dominant lethal alleles are usually eliminated from the NOTE population CARD 97 Table On the9.9 back! 94 95 96 97 98 100 98 101 99 100 101 102 103 102 103 104 105 Variations on Mendel NOTE CARD Fill out youron note card as indicated here. Answer the questions Variations Mendel on your own, please. •  Incomplete Dominance NOTE CARD •  neither allele is dominant over the other and On•  the back! of both alleles occurs expression – Redon + white = pink in F1 Variations Mendel – Not blending of alleles Variations Mendel » IF on in F2 you get 1 red, 2 pink, 1 white •  Incomplete Dominance •  neither allele is dominant over the other and •  Genes make proteins • red expression of both occurs –  gene makes redalleles pigment – Ronly ed +one white = pink F1only half the pigment – with allele, youinget – Not blending of alleles Figure 9.11a-0 » IF in F2 you get 1 red, 2 pink, 1 white Incomplete Dominance • § Genes make proteins Does not s...
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