Presentation on theme: "Mendelian Patterns of Inheritance"— Presentation transcript:
1 Mendelian Patterns of Inheritance Chapter 11Mader: Biology 8th Ed.
2 Law of Independent Assortment Human Genetic Disorders OutlineBlending InheritanceMonohybrid CrossLaw of SegregationModern GeneticsGenotype vs. PhenotypePunnett SquareDihybrid CrossLaw of Independent AssortmentHuman Genetic DisordersMader: Biology 8th Ed.
3 Studied science and mathematics at University of Vienna. Gregor MendelAustrian monk who formulated fundamental laws of heredity in early 1860s.Studied science and mathematics at University of Vienna.Conducted breeding experiments with the garden pea Pisum sativum.Carefully gathered and documented mathematical data from his experiments.Mader: Biology 8th Ed.
4 Blending InheritanceAt the time, most breeders believed parents of contrasting appearance always produce offspring of intermediate appearance.Mendel’s experiments helped him formulate the particulate theory of inheritance.Inheritance involves reshuffling of genes from generation to generation.Mader: Biology 8th Ed.
6 One-Trait Inheritance Mendel performed cross-breeding experiments between true-breeding plants.Chose varieties that differed in only one trait (monohybrid cross)Performed reciprocal crossesParental generation = PFirst generation offspring = F1Second generation offspring = F2Formulated law of segregationMader: Biology 8th Ed.
9 Each individual has two factors for each trait. Law of SegregationEach individual has two factors for each trait.The factors segregate during gamete formation.Each gamete contains only one factor from each pair of factors.Fertilization gives each new individual two factors for each trait.Mader: Biology 8th Ed.
10 Homozygous = identical alleles Heterozygous = different alleles Modern Genetics ViewEach 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 allelesHeterozygous = different allelesMader: Biology 8th Ed.
12 Genotype Versus Phenotype Refers to the alleles an individual receives at fertilization.PhenotypeRefers to the physical appearance of the individual.Mader: Biology 8th Ed.
13 Every possible combination of alleles is placed within the squares. Punnett SquareAll possible kinds of sperm are lined up on one axis, and all possible kinds of eggs are lined up on the other axis.Every possible combination of alleles is placed within the squares.Mader: Biology 8th Ed.
14 Genetic Inheritance in Humans Mader: Biology 8th Ed.
15 TestcrossA monohybrid testcross is used to determine if an individual with the dominant phenotype is homozygous dominant or heterozygous for a particular trait.Mader: Biology 8th Ed.
17 Two-Trait Inheritance Mendel performed cross using true-breeding plants differing in two traits.Dihybrid CrossObserved phenotypes among F2 plants.Formulated law of independent assortmentMader: Biology 8th Ed.
18 Law of Independent Assortment Each pair of factors segregates independently of the other pairs.All possible combinations of factors can occur in the gametes.Mader: Biology 8th Ed.
23 Human Genetic Disorders Autosome - Any chromosome other than a sex chromosome.When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder.When a genetic disorder is autosomal recessive, only aa individuals have the disorder.Carriers - Individuals unaffected by a disorder but can have an affected child.Mader: Biology 8th Ed.
26 Autosomal Recessive Disorders Tay-Sachs DiseaseProgressive deterioration of psychomotor functions.Cystic FibrosisMucus in bronchial tubes and pancreatic ducts is particularly thick and viscous.PhenylketonuriaLack enzyme for normal metabolism of phenylalanine.Mader: Biology 8th Ed.
27 Autosomal Dominant Disorders NeurofibromatosisTan or dark spots develop on skin and darken. Small, benign tumors may arise from fibrous nerve coverings.Huntington DiseaseNeurological disorder leading to progressive degeneration of brain cells, in turn causing severe muscle spasms and personality disorders.Mader: Biology 8th Ed.
28 Incomplete DominanceExhibited when the heterozygote has an intermediate phenotype between that of either homozygote.Mader: Biology 8th Ed.
30 Multiple Allelic Traits When a trait is controlled by multiple alleles, the gene exists in several allelic forms.ABO blood typesPhenotype GenotypeA IAIA,IAiB IBIB,IBiAB IAIBO iiMader: Biology 8th Ed.
31 Inheritance of Blood Type Mader: Biology 8th Ed.
32 Polygenic Inheritance Occurs when a trait is governed by two or more sets of alleles.Each dominant allele has a quantitative effect on the phenotype, and these effects are additive.Result in continuous variation of phenotypes.Mader: Biology 8th Ed.
34 Sickle-cell (incomplete dominance) TerminologyPleiotropy - A gene that affects more than one characteristic of an individual.Sickle-cell (incomplete dominance)Codominance - More than one allele is fully expressed.ABO blood type (multiple allelic traits)Epistasis - A gene at one locus interferes with the expression of a gene at a different locus.Human skin color (polygenic inheritance)Mader: Biology 8th Ed.
35 Environment and Phenotype Himalayan Rabbits - Enzyme coding for black fur is active only at low temperatures.Black fur only occurs on extremities.Mader: Biology 8th Ed.
36 Law of Independent Assortment Human Genetic Disorders ReviewBlending InheritanceMonohybrid CrossLaw of SegregationModern GeneticsGenotype vs. PhenotypePunnett SquareDihybrid CrossLaw of Independent AssortmentHuman Genetic DisordersMader: Biology 8th Ed.