Biology Sylvia S. Mader Michael Windelspecht Chapter 11 Mendelian Patterns of Inheritance Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

Biology, 9th ed,Sylvia Mader Chapter 11 Outline Mendelian Inheritance 11.1 Gregor Mendel 11.2 Mendel’s Laws 11.3 Extending the Range of Mendelian Genetics 2

Biology, 9th ed,Sylvia Mader Chapter 11 11.1 Gregor Mendel Mendelian Inheritance Concept of Blending Inheritance: Parents of contrasting appearance produce offspring of intermediate appearance Popular concept during Mendel’s time Mendel’s findings were in contrast with this He formulated the Particulate Theory of Inheritance Inheritance involves reshuffling of genes from generation to generation

Biology, 9th ed,Sylvia Mader Chapter 11 Gregor Mendel Mendelian Inheritance Austrian monk Studied science and mathematics at the University of Vienna Conducted breeding experiments with the garden pea Pisum sativum Carefully gathered and documented mathematical data from his experiments Formulated fundamental laws of heredity in the early 1860s Had no knowledge of cells or chromosomes Did not have a microscope

Biology, 9th ed,Sylvia Mader Chapter 11 Mendelian Inheritance Gregor Mendel Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Ned M. Seidler/Nationa1 Geographic Image Collection

Biology, 9th ed,Sylvia Mader Chapter 11 Gregor Mendel Mendelian Inheritance The garden pea: Organism used in Mendel’s experiments A good choice for several reasons: Easy to cultivate Short generation Normally self-pollinating, but can be cross-pollinated by hand True-breeding varieties were available Simple, objective traits 6

Biology, 9th ed,Sylvia Mader Garden Pea Anatomy Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Flower Structure anther stamen filament stigma style carpel ovules in ovary a.

Biology, 9th ed,Sylvia Mader Garden Pea Anatomy Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cutting away anthers Brushing on pollen from another plant All peas are yellow when one parent produces yellow seeds and the other parent produces green seeds.

Biology, 9th ed,Sylvia Mader Garden Pea Anatomy Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Characteristics Trait *Dominant *Recessive Stem length Tall Short Pod shape Inflated Constricted Seed shape Round Wrinkled Seed color Yellow Green Flower position Axial Terminal Flower color Purple White Pod color Green Yellow b.

Biology, 9th ed,Sylvia Mader Chapter 11 11.2 Mendel’s Laws Mendelian Inheritance Mendel performed cross-breeding experiments Used “true-breeding” (homozygous) plants Chose varieties that differed in only one trait (monohybrid cross) Performed reciprocal crosses Parental generation = P First filial generation offspring = F1 Second filial generation offspring = F2 Formulated the Law of Segregation

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio T = tall plant 3 tall t = short plant 1 short TT tt

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #12 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio T = tall plant 3 tall P generation t = short plant 1 short TT tt 12

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #13 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation T = tall plant 3 tall t = short plant 1 short TT tt P gametes T t 13

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #14 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation T = tall plant 3 tall t = short plant 1 short TT tt P gametes T t tt F1 generation Tt 14

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #15 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Allele Key Phenotypic Ratio P generation TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T sperm t 15

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #16 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation Allele Key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT sperm t 16

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #17 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. F1 generation Allele key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT Tt sperm t 17

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Monohybrid Cross done by Mendel Chapter 11 Slide #18 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation Allele Key Phenotypic Ratio TT tt T = tall plant 3 tall t = short plant 1 short P gametes T t F1 generation Tt eggs F1 gametes T t T TT Tt sperm t Tt 18

Monohybrid Cross done by Mendel Biology, 9th ed,Sylvia Mader Chapter 11 Slide #19 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation TT tt P gametes T t F1 generation Tt eggs F1 gametes T t T sperm TT Tt F2 generation t Tt tt Offspring Allele Key Phenotypic Ratio T = tall plant 19 3 tall t = short plant 1 short

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Law of Segregation: Each individual has a pair of factors (alleles) for each trait The factors (alleles) segregate (separate) during gamete (sperm & egg) formation Each gamete contains only one factor (allele) from each pair of factors Fertilization gives the offspring two factors for each trait

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Classical Genetics and Mendel’s Cross: Each trait in a pea plant is controlled by two alleles (alternate forms of a gene) Dominant allele (capital letter) masks the expression of the recessive allele (lower-case) Alleles occur on a homologous pair of chromosomes at a particular gene locus Homozygous = identical alleles Heterozygous = different alleles

Classical View of Homologous Chromosomes Biology, 9th ed,Sylvia Mader Chapter 11 Classical View of Homologous Chromosomes Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sister chromatids alleles at a gene locus G g G G g g Replication R r R R r r S s S S s s a. Homologous chromosomes have alleles for same genes at specific loci. b. Sister chromatids of duplicated chromosomes have same alleles for each gene. t T t t T T

Relationship Between Observed Phenotype and F2 Offspring Biology, 9th ed,Sylvia Mader Chapter 11 Relationship Between Observed Phenotype and F2 Offspring Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Characteristics F2Results Trait Dominant Recessive Dominant Recessive Ratio Stem length Tall Short 787 277 2.84:1 Inflated Pod shape Constricted 882 299 2.95:1 Seed shape Round Wrinkled 5,474 1,850 2.96:1 Seed color Yellow Green 6,022 2,001 3.01:1 Flower position Axial Terminal 651 207 3.14:1 705 224 3.15:1 Flower color Purple White Pod color Green Yellow 428 152 2.82:1 Totals: 14,949 5,010 2.98:1

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Genotype Refers to the two alleles an individual has for a specific trait If identical, genotype is homozygous If different, genotype is heterozygous Phenotype Refers to the physical appearance of the individual

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance A dihybrid cross uses true-breeding plants differing in two traits Mendel tracked each trait through two generations. Started with true-breeding plants differing in two traits The F1 plants showed both dominant characteristics F1 plants self-pollinated Observed phenotypes among F2 plants Mendel formulated the Law of Independent Assortment The pair of factors for one trait segregate independently of the factors for other traits All possible combinations of factors can occur in the gametes P generation is the parental generation in a breeding experiment. F1 generation is the first-generation offspring in a breeding experiment. F2 generation is the second-generation offspring in a breeding experiment

Dihybrid Cross Done by Mendel Biology, 9th ed,Sylvia Mader Dihybrid Cross Done by Mendel Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. × P generation TTGG ttgg P gametes TG tg F1 generation TtGg eggs F1 gametes TG Tg tG tg TG TTGG TTGg TtGG TtGg F2 generation Tg TTGg TTgg TtGg Ttgg sperm tG TtGG TtGg ttGG ttGg tg TtGg Ttgg ttGg ttgg Offspring Allele Key Phenotypic Ratio T = tall plant 9 tall plant, green pod t = short plant 3 tall plant, yellow pod G = green pod 3 short plant, green pod g = Yellow pod 1 short plant, yellow pod

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A a B b Parent cell has two pairs of homologous chromosomes.

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #28 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A a a B B b b either A a B b Parent cell has two pairs of homologous chromosomes. 28

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #29 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A a a B B b b either A a B b or A A a a Parent cell has two pairs of homologous chromosomes. b b B B 29

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #30 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A a a B B b b either A a B b or A A a a Parent cell has two pairs of homologous chromosomes. b b B B All orientations of ho- mologous chromosomes are possible at meta- phase I in keeping with the law of independent assortment. 30

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #31 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A B B A A a a B B b b a a b b either A a B b or A A a a Parent cell has two pairs of homologous chromosomes. b b B B All orientations of ho- mologous chromosomes are possible at metaphase I in keeping with the law of independent assortment. 31

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #32 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A B B A A a a B B b b a a b b either A a B b A A or b b A A a a Parent cell has two pairs of homologous chromosomes. b b B B a a B B All orientations of ho- mologous chromosomes are possible at metaphase I in keeping with the law of independent assortment. 32

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #33 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A A B B A A a a B B b b a a b b either A a B b A A or b b Parent cell has two pairs of homologous chromosomes. A A a a b b B B a a B B All orientations of ho- mologous chromosomes are possible at meta- phase I in keeping with the law of independent assortment. At metaphase II, each daughter cell has only one member of each homologous pair in keeping with the law of segregation 33

Independent Assortment and Segregation during Meiosis Biology, 9th ed,Sylvia Mader Independent Assortment and Segregation during Meiosis Chapter 11 Slide #34 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A B A A AB B B A B A A a a B B b b a a a b b b ab either a b A a B b A A A b or b b Ab A Parent cell has two pairs of homologous chromosomes. b A A a a b b B B a a a B B B aB a B All orientations of ho- mologous chromosomes are possible at metaphase I in keeping with the law of Independent assortment. At metaphase II, each daughter cell has only one member of each homologous pair in keeping with the law of segregation All possible combi - tions of chromosomes and alleles occur in the gametes as suggested by Mendel's two laws. 34

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Punnett Square Table listing all possible genotypes resulting from a cross All possible sperm genotypes are lined up on one side All possible egg genotypes are lined up on the other side Every possible zygote genotypes are placed within the squares

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Punnett Square Allows us to easily calculate probability, of genotypes and phenotypes among the offspring Punnett square in next slide shows a 50% (or ½) chance The chance of E = ½ The chance of e = ½ An offspring will inherit: The chance of EE =½  ½=¼ The chance of Ee =½  ½=¼ The chance of eE =½  ½=¼ The chance of ee =½  ½=¼

Biology, 9th ed,Sylvia Mader Punnett Square Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parents Ee Ee eggs E e E EE Ee spem Punnett square e Ee ee Offspring Allele key Phenotypic Ratio E = unattached earlobes 3 unattached earlobes e = attached earlobes 1 attached earlobes

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Testcrosses Individuals with recessive phenotype always have the homozygous recessive genotype However, individuals with dominant phenotype have indeterminate genotype May be homozygous dominant, or Heterozygous A testcross determines the genotype of an individual having the dominant phenotype

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Two-trait testcross: An individual with both dominant phenotypes is crossed with an individual with both recessive phenotypes. If the individual with the dominant phenotypes is heterozygous for both traits, the expected phenotypic ration is 1:1:1:1. 39

Biology, 9th ed,Sylvia Mader Chapter 11 Mendel’s Laws Mendelian Inheritance Genetic disorders are medical conditions caused by alleles inherited from parents Autosome - Any chromosome other than a sex chromosome (X or Y) Genetic disorders caused by genes on autosomes are called autosomal disorders Some genetic disorders are autosomal dominant An individual with AA has the disorder An individual with Aa has the disorder An individual with aa does NOT have the disorder Other genetic disorders are autosomal recessive An individual with AA does NOT have the disorder An individual with Aa does NOT have the disorder, but is a carrier An individual with aa DOES have the disorder

Autosomal Recessive Pedigree Biology, 9th ed,Sylvia Mader Autosomal Recessive Pedigree Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. I aa A? II A? Aa Aa A? Generations * III Aa Aa A? A? IV aa aa A? Key aa = affected Aa = carrier (unaffected) AA = unaffected A? = unaffected (one allele unknown) Autosomal recessive disorders • Most affected children have unaffected parents. • Heterozygotes (Aa) have an unaffected phenotype. • Two affected parents will always have affected children. • Close relatives who reproduce are more likely to have affected children. • Both males and females are affected with equal frequency.

Autosomal Dominant Pedigree Biology, 9th ed,Sylvia Mader Chapter 11 Autosomal Dominant Pedigree Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. I Aa Aa * Generations II aa Aa A? aa aa aa III Aa Aa aa aa aa aa Key AA = affected Aa = affected A? = affected (one allele unknown) aa = unaffected Autosomal dominant disorders • Affected children will usually have an affected parent. • Heterozygotes (Aa) are affected. • Two affected parents can produce an unaffected child. • Two unaffected parents will not have affected children. • Both males and females are affected with equal frequency.

11.3 Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 11.3 Extending the Range of Mendelian Genetics Mendelian Inheritance Some traits are controlled by multiple alleles (multiple allelic traits) The gene exists in several allelic forms (but each individual only has two alleles) ABO blood types The alleles: IA = A antigen on red blood cells, anti-B antibody in plasma IB = B antigen on red blood cells, anti-A antibody in plasma i = Neither A nor B antigens on red blood cells, both anti-A and anti-B antibodies in plasma The ABO blood type is also an example of codominance More than one allele is fully expressed Both IA and IB are expressed in the presence of the other

Biology, 9th ed,Sylvia Mader Chapter 11 ABO Blood Type Mendelian Inheritance Phenotype A B AB O Genotype IAIA, IAi IBIB, IBi IAIB ii

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Extending the Range of Mendelian Genetics Mendelian Inheritance Incomplete Dominance: Heterozygote has a phenotype intermediate between that of either homozygote Homozygous red has red phenotype Homozygous white has white phenotype Heterozygote has pink (intermediate) phenotype Phenotype reveals genotype without a test cross

Biology, 9th ed,Sylvia Mader Chapter 11 Incomplete Dominance Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. R R R R 1 2 1 2 eggs R R 1 2 R 1 R R R R 1 1 1 2 sperm Key 1 R R red 1 1 R 2 R R pink 2 1 2 1 R R white 2 2 R R R R 1 2 2 2 Offspring

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Extending the Range of Mendelian Genetics Mendelian Inheritance Human examples of incomplete dominance: Incomplete penetrance The dominant allele may not always lead to the dominant phenotype in a heterozygote Many dominant alleles exhibit varying degrees of penetrance Example: polydactyly Extra digits on hands, feet, or both Not all individuals who inherit the dominant polydactyly allele will exhibit the trait 47

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Mendelian Inheritance Extending the Range of Mendelian Genetics Pleiotropy occurs when a single mutant gene affects two or more distinct and seemingly unrelated traits. Marfan syndrome is pleiotropic and results in the following phenotypes: disproportionately long arms, legs, hands, and feet a weakened aorta poor eyesight

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Extending the Range of Mendelian Genetics Mendelian Inheritance Polygenic Inheritance: Occurs when a trait is governed by two or more genes having different alleles Each dominant allele has a quantitative effect on the phenotype These effects are additive Results in continuous variation of phenotypes within a population The traits may also be affected by the environment Examples Human skin color Height Eye color

Polygenic Inheritance Biology, 9th ed,Sylvia Mader Polygenic Inheritance Chapter 11 Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P generation F1 generation F2 generation 20 — 64 15 — 64 Proportion of Population 6 — 64 1 — 64 aabbcc Aabbcc AaBbcc AaBbCc AABbCc AABBCc AABBCC Genotype Examples

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Extending the Range of Mendelian Genetics Mendelian Inheritance X-Linked Inheritance In mammals The X and Y chromosomes determine gender Females are XX Males are XY

Extending the Range of Mendelian Genetics Biology, 9th ed,Sylvia Mader Chapter 11 Extending the Range of Mendelian Genetics Mendelian Inheritance X-Linked Inheritance The term X-linked is used for genes that have nothing to do with gender X-linked genes are carried on the X chromosome. The Y chromosome does not carry these genes Discovered in the early 1900s by a group at Columbia University, headed by Thomas Hunt Morgan. Performed experiments with fruit flies They can be easily and inexpensively raised in simple laboratory glassware Fruit flies have the same sex chromosome pattern as humans

X-Linked Recessive Pedigree Biology, 9th ed,Sylvia Mader Chapter 11 X-Linked Recessive Pedigree Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. XBXB XbY grandfather XBY XBXb daughter XBY XbXb XbY XBY XBXB XBXb XbY grandson Key XBXB = Unaffected female XBXb = Carrier female XbXb = Color-blind female XbY = Unaffected male XbY = Color-blind male X-Linked Recessive Disorders • More males than females are affected. • An affected son can have parents who have the normal phenotype. • For a female to have the characteristic, her father must also have it. Her mother must have it or be a carrier. • The characteristic often skips a generation from the grandfather to the grandson. • If a woman has the characteristic, all of her sons will have it.

Biology, 9th ed,Sylvia Mader Chapter 11 Muscular Dystrophy Mendelian Inheritance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. fibrous tissue abnormal muscle normal tissue (Abnormal): Courtesy Dr. Rabi Tawil, Director, Neuromuscular Pathology Laboratory, University of Rochester Medical Center; (Boy): Courtesy Muscular Dystrophy Association; (Normal): Courtesy Dr. Rabi Tawil, Director, Neuromuscular Pathology Laboratory, University of Rochester Medical Center.