Inheritance:Inheritance:

Mendel’s LawsMendel’s Laws

and and

Pedigrees and DiseasesPedigrees and Diseases

Mendel’s Laws of InheritanceMendel’s Laws of Inheritance

Law of SegregationLaw of Segregation ““Elementen” separate in the gametesElementen” separate in the gametes Homologous chromosomes (and the Homologous chromosomes (and the

homologous genes found on each homologous genes found on each chromosome) are separated during meiosis.chromosome) are separated during meiosis.

Law of Independent AssortmentLaw of Independent Assortment

Law of SegregationLaw of Segregation

Mendel’s Laws of InheritanceMendel’s Laws of Inheritance

Law of SegregationLaw of Segregation ““Elementen” separate in the gametesElementen” separate in the gametes Homologous chromosomes (and the homologous Homologous chromosomes (and the homologous

genes found on each chromosome) are separated genes found on each chromosome) are separated during meiosis.during meiosis.

Law of Independent AssortmentLaw of Independent Assortment Inheritance of one “elementen” does not influence inheritance of another Inheritance of one “elementen” does not influence inheritance of another

“elementen”“elementen” Genes on different chromosomes are packaged into gametes at randomGenes on different chromosomes are packaged into gametes at random

Independent AssortmentIndependent AssortmentR =roundY =yellow

Independent Assortment –Dihybrid CrossIndependent Assortment –Dihybrid Cross

Dihybrids

ExampleExample

Heterozygous for round peas with white Heterozygous for round peas with white flowersflowers

XX

Wrinkled peas and Homozygous for purple Wrinkled peas and Homozygous for purple flowersflowers

ExampleExample

Homozygous for yellow peas and Homozygous for yellow peas and heterozygous for axial flowersheterozygous for axial flowers

XX

Heterozygous for yellow peas and Heterozygous for yellow peas and heterozygous for axial flowersheterozygous for axial flowers

ExampleExample

Homozygous for purple flowers and Homozygous for purple flowers and heterozygous for axial flowers and heterozygous for axial flowers and

heterozygous for round peasheterozygous for round peas

XX

White flowers and heterozygous for axial White flowers and heterozygous for axial flowers and homozygous for round peasflowers and homozygous for round peas

The Product RuleThe Product Rule

The probability that 2 independent events The probability that 2 independent events will both occur equals the product of the will both occur equals the product of the chance that either will occur alonechance that either will occur alone

Probability of obtaining a plant with purple Probability of obtaining a plant with purple flowers and green peas = probability of a flowers and green peas = probability of a plant with purple flowers X probability of a plant with purple flowers X probability of a plant with green peasplant with green peas

ExampleExample

Heterozygous purple flowers and Heterozygous purple flowers and Heterozygous yellow peasHeterozygous yellow peas

XX

Heterozygous purple flowers and green Heterozygous purple flowers and green peaspeas

PedigreesPedigrees

Symbolic representations of family relationships and inheritance of a trait

Allow evaluation of the mode of inheritance

Autosomal dominant Autosomal recessive

Symbols used in pedigrees

AlbinismAlbinism

Evaluating Mode of InheritanceEvaluating Mode of Inheritance

Autosomal Dominant? Autosomal Recessive?

PolydactylyPolydactyly

Evaluating Mode of InheritanceEvaluating Mode of Inheritance

Autosomal Dominant? Autosomal Recessive?

Crohn’s DiseaseCrohn’s Disease

Autoimmune disease Autoimmune disease Immune system attacks selfImmune system attacks self Inflammation of digestive tractInflammation of digestive tract

SymptomsSymptoms Abdominal pain and diarrheaAbdominal pain and diarrhea

Evaluating Mode of InheritanceEvaluating Mode of Inheritance

Autosomal Dominant? Autosomal Recessive?

Spinal Muscular AtrophySpinal Muscular Atrophy

Severe muscle weakness from birthSevere muscle weakness from birth Loss of motor neurons in the spinal cordLoss of motor neurons in the spinal cord

Evaluating Mode of InheritanceEvaluating Mode of Inheritance

Autosomal Dominant?

Evaluating Mode of InheritanceEvaluating Mode of Inheritance

Autosomal Recessive?

Get to Know Your ClassmateGet to Know Your Classmate

Pair up (preferably) with Pair up (preferably) with someone you do not knowsomeone you do not know

Pick a trait or disease found in Pick a trait or disease found in your family or you partner’s your family or you partner’s familyfamily

Draw a pedigree depicting the Draw a pedigree depicting the inheritance of the trait/diseaseinheritance of the trait/disease

Try to determine the mode of Try to determine the mode of inheritanceinheritance

DadMom

Vicki Johnny

Elizabeth Mildred BobJoe

Zoey Savannah Jasmine

ElizabethJeffreyJerryJimmyJoey Doug Stuart

DAM Roger Billy

Marion NormBlondeness in Professor Morrissette’s Family