Mendelian Patterns of Inheritance

Mendelian Patterns of Inheritance
Chapter 11 BIOL1000 Dr. Mohamad H. Termos

Biology, 9th ed,Sylvia Mader
Chapter 11 Gregor Mendel Austrian monk Studied science and math Breeding experiments with the garden pea Mathematical data from his experiments Formulated fundamental laws of heredity in early 1860s Mendelian Inheritance

One-Trait Inheritance
Biology, 9th ed,Sylvia Mader Chapter 11 One-Trait Inheritance Cross-breeding experiments Used “true-breeding” (homozygous) plants Chose pea plants that differed in only one trait (monohybrid cross) Parents = P First offspring = F1 Second offspring (result of crossing F1) = F2 Results: P= Green pods X Yellow pods (true breeding) F1= all green pods Green pod X Green pod F2= 3 Green pods : 1 yellow pod Mendelian Inheritance

Law of Segregation Chapter 11 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 Fertilization gives the offspring two factors for each trait Mendelian Inheritance

Modern Genetics View and Homologous Chromosomes
Biology, 9th ed,Sylvia Mader Chapter 11 Modern Genetics View and Homologous Chromosomes Each trait in a pea plant is controlled by two alleles 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 (TT or tt) Heterozygous = different alleles (Tt) Mendelian Inheritance

Chapter 11 Modern Genetics View Allele from green pods (G) is dominant to yellow pod allele (g) Green pods = ________ or ________ Yellow pods = _____________ Mendelian Inheritance

Chapter 11 Results P= Green pods (GG) X Yellow pods (gg) F1= all green pods (Gg) Green pod (Gg) X Green pod (Gg) F2= 3 Green pods(Gg or GG):1 yellow pod (gg) Mendelian Inheritance

Mendel’s Monohybrid Crosses:
Biology, 9th ed,Sylvia Mader Chapter 11 Mendelian Inheritance

Genotype Versus Phenotype
Biology, 9th ed,Sylvia Mader Chapter 11 Genotype Versus Phenotype Genotype Refers to the two alleles for a trait Homozygous Dominant or recessive Heterozygous Phenotype Physical appearance of the trait GG Homozygous dom. Green pods Gg Heterozygous Green pods gg Homozygous rec. Yellow pods Mendelian Inheritance

Chapter 11 Practice question In rabbits B= black fur (dominant) and b= white fur (recessive) What is the genotype of a rabbit with white fur? Black fur? Mendelian Inheritance

Chapter 11 Punnett Square Table listing all possible genotypes resulting from a cross Sperm genotypes are lined up on one side Egg genotypes are lined up on the other side Possible zygote genotypes are placed within the squares Mendelian Inheritance

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

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

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

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

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

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

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

Chapter 11 A punnett square for the true breeding green pods (GG) with yellow pods (gg) Mendelian Inheritance

Chapter 11 Punnett Square G g Gg G is the allele for green pods g is the allele for yellow pods P= GG X gg (genotypes) F1= 4/4 Gg (genotypes) Phenotypic ratios 4/4 Green pods Mendelian Inheritance

Chapter 11 G g GG Gg gg - F1= Gg X Gg (genotypes) - F2= ¼ GG ½ Gg ¼ gg - Phenotypic ratios: ¾ Green pods ¼ yellow pods Mendelian Inheritance

Chapter 11 Mendelian Inheritance

Chapter 11 Practice question Draw a punnett square for a cross between a homozygous recessive plant and a heterozygous plant. The dominant allele (F) is for purple flowers and the recessive allele (f) is for white flowers. What are the genotypes of the offspring? Phenotypes? Mendelian Inheritance

Practice question - Answer
Biology, 9th ed,Sylvia Mader Chapter 11 Practice question - Answer Ff X ff F f Ff ff Mendelian Inheritance

Biology, 9th ed,Sylvia Mader Chapter 11 Practice question - Answer Ff X ff Genotypic ratios? 50% ff 50% Ff Phenotypic ratios 50% white flowers 50% purple flowers F f Ff ff Mendelian Inheritance

Chapter 11 Dominant Vs Recessive Recessive phenotype always = homozygous recessive genotype However, dominant phenotype = indeterminate genotype May be homozygous dominant, or Heterozygous Mendelian Inheritance

Chapter 11 Test Cross Test cross determines genotype of individual having dominant phenotype Does a tall plant have genotype TT or Tt? Cross with a short plant (tt) and look at their offspring. Mendelian Inheritance

Biology, 9th ed,Sylvia Mader Chapter 11 Practice question - Answer After crossing tall plant with a short the result is: -50% short -50% tall What is genotype of tall parent? Tt t T Tt tt Mendelian Inheritance

Biology, 9th ed,Sylvia Mader Chapter 11 Practice question - Answer After crossing tall plant with a short the result is: -100% tall What is genotype of tall parent? TT t T Tt Mendelian Inheritance

Chapter 11 Practice question A pea plant that has round seeds (R is dominant)is crossed with a pea plant that has wrinkled seeds (r is recessive). The cross produces both round and wrinkled seeds. What must be the genotype of the pea plant with the round seeds? What are the genotypic and phenotypic ratios of the offspring? Mendelian Inheritance

Practice Question - Answer
Biology, 9th ed,Sylvia Mader Chapter 11 Practice Question - Answer Plant with round seeds is either RR or Rr Crossed with wrinkled seeds – rr r R Rr r R Rr rr Mendelian Inheritance

Practice Question - Answer
Biology, 9th ed,Sylvia Mader Chapter 11 Practice Question - Answer Parent must have Rr genotype Offspring are ½ Rr Round seeds ½ rr wrinkled seeds Mendelian Inheritance

Chapter 11 If 300 offspring were produced from the previous cross, how many of those will have round seeds? Mendelian Inheritance

Chapter 11 Answer Percentage X total offspring ½ or 50% X 300= 150 offspring will have round seeds Mendelian Inheritance

Two-Trait Inheritance
Biology, 9th ed,Sylvia Mader Chapter 11 Two-Trait Inheritance Dihybrid cross uses true-breeding (homozygous) plants differing in two traits (TTGG X ttgg) Mendelian Inheritance

Two-Trait Inheritance
Biology, 9th ed,Sylvia Mader Chapter 11 Two-Trait Inheritance TTGGxttgg Possible Gametes: TG and tg Mendelian Inheritance

Chapter 11 All offspring are tall with green pods TG tg TtGg Mendelian Inheritance

Chapter 11 TtGg X TtGg Possible gametes: TG, Tg, tG, tg Page 194 in book Mendelian Inheritance

Two-Trait (Dihybrid) Cross
Biology, 9th ed,Sylvia Mader Two-Trait (Dihybrid) Cross Chapter 11 Mendelian Inheritance

Law of Independent Assortment
Biology, 9th ed,Sylvia Mader Chapter 11 Law of Independent Assortment Alleles for one trait segregate independently of other alleles All possible combinations of alleles can occur in the gametes Mendelian Inheritance

Chapter 11 Incomplete Dominance Heterozygote has phenotype between that of either homozygote Homozygous red has red phenotype (R1) Homozygous white has white phenotype (R2) Heterozygote has pink (intermediate) phenotype (R1 R2) Phenotype reveals genotype without test cross Mendelian Inheritance

Incomplete Dominance Chapter 11 Mendelian Inheritance

Chapter 11 Practice question If you crossed a pink flowering plant with a red flowering plant what are the genotypic and phenotypic ratios of the offspring? Mendelian Inheritance

Chapter 11 Answer Pink genotype is R1R2 Red genotype is R1R1 Genotypic ratio: 2/4 R1R1 2/4 R1R2 Phenotypic ratio: 2/4 red 2/4 pink R1 R2 R1R1 R1R2 Mendelian Inheritance

Multiple Allelic Traits
Biology, 9th ed,Sylvia Mader Chapter 11 Multiple Allelic Traits Some traits controlled by multiple alleles The gene exists in several allelic forms (but each individual only has two) ABO blood types Mendelian Inheritance

Chapter 11 ABO Alleles The alleles: IA IB i Phenotype (Blood Type) Genotype A (actually AA or AO) IAIA or IAi B (actually BB or BO) IBIB or IBi AB IAIB O (actually OO) ii Mendelian Inheritance

Inheritance of Blood Type
Biology, 9th ed,Sylvia Mader Inheritance of Blood Type Chapter 11 Mendelian Inheritance

Chapter 11 Practice question If a mother is blood type A and a father is blood type B is it possible for them to have a baby with O blood type? Mendelian Inheritance

Chapter 11 Answer Possible genotypes: father: IA IA or IA i mother: IB IB or IB i If they are IAi X IBi then ¼ offspring will be ii IA i IB IAIB IB i IA i ii Mendelian Inheritance

Chapter 11 Practice question A mother has blood type A (both parents are AB) and a father has parents that both have O blood type. They have a baby with O blood type- did they bring home the wrong baby, is the father really the father of the child, or is this their child? Mendelian Inheritance

Chapter 11 Answer Mother has A Blood type and both her parents have AB blood type A B AA AB BB Mother must have AA genotype if her blood type is A Mendelian Inheritance

Chapter 11 Answer Father has both parents with O blood type i ii All of their children must be O blood type so father has O blood type with genotype ii Mendelian Inheritance

Chapter 11 Answer Mother has genotype AA and father has ii A baby with O blood type is not their baby- it is not possible Wrong baby? Or father not really the father? Is it possible for the mother to ever have offspring with O blood type? A i Ai Mendelian Inheritance

Polygenic Inheritance
Biology, 9th ed,Sylvia Mader Chapter 11 Polygenic Inheritance Occurs when a trait is governed by two or more genes having different alleles Result in continuous variation of phenotypes height, skin color, eye color Mendelian Inheritance

Polygenic Inheritance
Biology, 9th ed,Sylvia Mader Polygenic Inheritance Chapter 11 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 Mendelian Inheritance

Chapter 11 How many pairs of chromosomes in humans? Total # chromosomes? -22 pairs are autosomes -23rd pair are the sex chromosomes (X and Y) XY=male XX=female Some traits are located on the X chromosome Male= Mars symbol, Female = Venus symbol Mendelian Inheritance

Chapter 11 X-linked Color blindness The alleles for the red- and green-sensitive pigments are on the X chromosome. Muscular dystrophy Wasting away of the muscle due to missing protein Hemophilia Absence or minimal presence of clotting factor VIII or clotting factor IX Affected person’s blood either does not clot or clots very slowly. Mendelian Inheritance

Chapter 11 Mendelian Inheritance

Chapter 11 X linked genes Eye color in flies - red (R) or white (r) Males can be: XRY or XrY trait determined by x chromosome (1 allele) Females can be XRXR or XRXr or XrXr trait determined by 2 alleles Mendelian Inheritance

Chapter 11 White eyed female X red eyed male Mother homozygous recessive Father has dominant allele Offspring females: 100% heterozygous (red eyes) males: 100% recessive (white eyes) Xr XR XRXr Y XrY Mendelian Inheritance

Chapter 11 Genetic disorders Many disorders are genetic and can be passed from parents to offspring Can be dominant traits or recessive Can also be X linked Mendelian Inheritance

Autosomal Recessive Disorders
Biology, 9th ed,Sylvia Mader Chapter 11 Autosomal Recessive Disorders Methemoglobinemia Relatively harmless disorder Accumulation of methemoglobin in the blood causes skin to appear bluish-purple Cystic Fibrosis Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscous Mendelian Inheritance

Chapter 11 Methemoglobinemia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Courtesy Division of Medical Toxicology, University of Virginia Mendelian Inheritance

Chapter 11 Cystic Fibrosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cl- Cl- H2O Cl- H2O Cl- Cl- H2O nebulizer defective channel percussion vest thick mucus © Pat Pendarvis Mendelian Inheritance

Autosomal Dominant Disorders
Biology, 9th ed,Sylvia Mader Chapter 11 Autosomal Dominant Disorders Osteogenesis Imperfecta Gene mutation  Weakened, brittle bones Hereditary Spherocytosis Gene mutation  Red blood cells become spherical, fragile, and burst easily Mendelian Inheritance

Chapter 11 Pedigree Shows the pattern of inheritance Squares are male Circles are female Shaded shapes have the trait Mendelian Inheritance

Autosomal Dominant Pedigree Chart
Biology, 9th ed,Sylvia Mader Autosomal Dominant Pedigree Chart Chapter 11 Mendelian Inheritance

Autosomal Recessive Pedigree Chart
Biology, 9th ed,Sylvia Mader Autosomal Recessive Pedigree Chart Chapter 11 Mendelian Inheritance

Mendelian Patterns of Inheritance

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