Sylvia S. Mader Copyright The McGraw Hill Companies Inc. Permission required for reproduction or...

Sylvia S. Mader

Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY10th Edition

Mendelian Patterns of Inheritance

Chapter 11: pp. 189 - 210

1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Parents

eggs

Ee Ee

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Outline

Blending InheritanceMonohybrid Cross

Law of SegregationModern Genetics

Genotype vs. PhenotypePunnett Square

Dihybrid CrossLaw of Independent Assortment

Human Genetic Disorders

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Gregor Mendel

Austrian monk 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 Formulated fundamental laws of heredity in early

1860s Had no knowledge of cells or chromosomes Did not have a microscope

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Gregor Mendel


© Ned M. Seidler/Nationa1 Geographic Image Collection

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Fruit and Flower of the Garden Pea


a.

Flower Structure

filamentanther

stamen

stigmastyle

ovules inovary

carpel

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Garden Pea Traits Studied by Mendel


Cutting awayanthers

Brushing onpollen fromanother plant

All peas are yellow whenone parent produces yellowseeds and the other parentproduces green seeds.

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Blending Inheritance

Theories of inheritance in Mendel’s time:Based on blendingParents of contrasting appearance produce

offspring of intermediate appearanceMendel’s findings were in contrast with this

He formulated the particulate theory of inheritance

Inheritance involves reshuffling of genes from generation to generation

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One-Trait Inheritance

Mendel performed cross-breeding experimentsUsed “true-breeding” (homozygous) plantsChose varieties that differed in only one trait

(monohybrid cross)Performed reciprocal crosses

Parental generation = PFirst filial generation offspring = F1 Second filial generation offspring = F2

Formulated the Law of Segregation

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Mendel’s Monohybrid Crosses:An Example


TT tt

tT

P generation

P gametes

F1 gametes

F2 generation

F1 generation

Tt

T t

sper

m

T

t

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Tt tt

Offspring

Phenotypic Ratio

short1tall3

Allele KeyT = tall plantt = short plant

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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

Fertilization gives the offspring two factors for each trait

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Modern Genetics View

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

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Homologous Chromosomes

Replication

alleles at agene locus

sister chromatids

b. Sister chromatids of duplicated chromosomes have same alleles for each gene.

a. Homologous chromosomes have alleles for same genes at specific loci.

G

R

S

t

G

R

S

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G

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S

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g

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Genotype versus Phenotype

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

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Genotype versus Phenotype

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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

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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

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Punnett Square Showing Earlobe Inheritance Patterns

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Parents

Ee Ee

eggs

spem

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Offspring

E e

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EeEE

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Allele key Phenotypic Ratio

unattached earlobes3

1

E = unattached earlobese = attached earlobes attached earlobes

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Monohybrid Test cross

Individuals with recessive phenotype always have the homozygous recessive genotype

However, individuals with dominant phenotype have indeterminate genotype

May be homozygous dominant, or

Heterozygous

Test cross determines genotype of individual having dominant phenotype

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One-Trait Test Cross

Insert figure 11.7a here

Phenotypic Ratio

eggs

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Allele Key

short1tall1

T = tall plantt = short plant


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One-Trait Test Cross


b.

tT

Tt

Offspring

eggssperm

TT tt

Allele Key

Phenotypic RatioAll tall plants

T = tall plantt = short plant

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Two-Trait Inheritance Dihybrid cross uses true-breeding plants differing in two

traits

Observed phenotypes among F2 plants

Formulated 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 Mendel tracked each trait through two generations.

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

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Two-Trait (Dihybrid) Cross


TtGg

ttgg

TTGG

Offspring

P generation

P gametes

F2 generation

F1 generation

F1 gametes

eggssp

erm

TG Tg

TG

Tg

tg

tG

tG tg

tgTG

TTGg TtGG TtGg

TTGg Ttgg

TtGG ttGG ttGg

TtGg Ttgg ttGg

ttggTTGG

TtGg

TTgg

TtGg

Allele Key====

TtGg

tall plantshort plantgreen podyellow pod

Phenotypic Ratio9 tall plant, green pod3 tall plant, yellow pod3 short plant, green pod1 short plant, yellow pod

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Independent Assortment and Segregation during Meiosis


Parent cell has twopairs of homologouschromosomes.

All possible combina-tions of chromosomesand alleles occur inthe gametes assuggested by Mendel'stwo laws.

All orientations of ho-mologous chromosomesare possible at meta-phase I in keeping withthe law of independentassortment.

At metaphase II, eachdaughter cell has onlyone member of eachhomologous pair inkeeping with the law ofsegregation.

A

A A

A A

A

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AB

ab

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aB

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bA

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a a

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bA

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either

or

Animation

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Human Genetic Disorders 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 disorder

Other genetic disorders are autosomal recessive An individual with AA does NOT have disorder An individual with Aa does NOT have disorder, but is a carrier An individual with aa DOES have the disorder

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Autosomal Recessive Disorders

Tay-Sachs Disease Progressive deterioration of psychomotor functions

Cystic Fibrosis Mucus in bronchial tubes and pancreatic ducts is

particularly thick and viscous

Phenylketonuria (PKU) Lack enzyme for normal metabolism of phenylalanine

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Cystic Fibrosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cl-

H2O

H2O

H2O

Cl-

Cl-

Cl-

Cl-

thick mucus

defectivechannel

nebulizer

percussionvest

© Pat Pendarvis

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MethemoglobinemiaCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Courtesy Division of Medical Toxicology, University of Virginia

Animation

Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

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Autosomal Dominant Disorders

NeurofibromatosisTan or dark spots develop on skin and darken Small, benign tumors may arise from fibrous

nerve coveringsHuntington Disease

Neurological disorderProgressive degeneration of brain cells

Severe muscle spasmsPersonality disorders

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Incomplete Dominance

Heterozygote has 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 test cross

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Incomplete DominanceCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

R1 R2

R1

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redpinkwhite

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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 The alleles:

IA = A antigen on red cells, anti-B antibody in plasma IB = B antigen on red cells, anti-AB antibody in plasma I = Neither A nor B antigens, both antibodies

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Multiple Allelic Traits

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Pleioptropic Effects

Pleiotropy occurs when a single mutant gene affects two or more distinct and seemingly unrelated traits. Marfan syndrome have disproportionately

long arms, legs, hands, and feet; a weakened aorta; poor eyesight

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Marfan Syndrome


(Left): © AP/Wide World Photos; (Right): © Ed Reschke

Chest wall deformitiesLong, thin fingers, arms, legsScoliosis (curvature of the spine)Flat feetLong, narrow faceLoose joints

Skeleton SkinLungsEyes

Mitral valveprolapse

Lens dislocationSevere nearsightedness Collapsed lungs

Stretch marks in skinRecurrent herniasDural ectasia: stretching of the membrane that holds spinal fluid

Enlargementof aorta

Heart and blood vessels

AneurysmAortic wall tear

Connectivetissue defects

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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

Result in continuous variation of phenotypes

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Frequency Distributions in Polygenic Inheritance


F2 generation

F1 generation

P generation

aabbcc

Aabbcc

AaBbcc

AaBbCc

AABbCc

AABBCc

AABBCC

Genotype Examples

164—

6—64

15—64

20—64

Prop

ortio

n of

Pop

ulat

ion

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X – Linked Inheritance In mammals

The X and Y chromosomes determine gender Females are XX Males are XY

The term X-linked is used for genes that have nothing to do with gender 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

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Human X-Linked Disorders Several X-linked recessive disorders occur in humans:

Color blindness The allele for the blue-sensitive protein is autosomal The alleles for the red- and green-sensitive pigments are on the X

chromosome. Menkes syndrome

Caused by a defective allele on the X chromosome Disrupts movement of the metal copper in and out of cells.

Muscular dystrophy Wasting away of the muscle

Adrenoleukodystrophy X-linked recessive disorder Failure of a carrier protein to move either an enzyme or very long chain fatty

acid into peroxisomes. Hemophilia

Absence or minimal presence of a clotting factor VIII, or clotting factor IX Affected person’s blood either does not clot or clots very slowly.

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Muscle DystrophyCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(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.

abnormalmuscle

normaltissue

fibroustissue

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Terminology Pleiotropy

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)

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Review

Blending InheritanceMonohybrid Cross

Law of SegregationModern Genetics

Genotype vs. Phenotype Punnett Square

Dihybrid Cross Law of Independent Assortment

Human Genetic Disorders

Sylvia S. Mader

Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY10th Edition

Mendelian Patterns of Inheritance

Chapter 11: pp. 189 - 210

44


Parents

eggs

Ee Ee

spem

Punn

ett s

quar

e

Offspring

E e

E

e

Ee

EeEE

ee

TT tt

tT

Tt

eggs

sper

m

Offspring

T t

T

t

TT Tt

Tt tt

Sylvia S. Mader Copyright The McGraw Hill Companies Inc. Permission required for reproduction or...

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