Observable Observable Patterns of Patterns of InheritanceInheritance

Can you do this?Can you do this?

Terms to KnowTerms to Know

ProbabilityProbability True-breedingTrue-breeding HybridHybrid SegregationSegregation TraitsTraits GenesGenes

HomozygousHomozygous HeterozygousHeterozygous PhenotypePhenotype GenotypeGenotype DominantDominant RecessiveRecessive

GenesGenes Chemical factors that determine Chemical factors that determine

traits (units of information)traits (units of information) Analogy: Genes are like a Analogy: Genes are like a

combination of ingredients in a combination of ingredients in a recipe. They code for a specific recipe. They code for a specific food.food.

Passed from parents to offspringPassed from parents to offspring Each has a specific location (Each has a specific location (locuslocus) )

on a chromosomeon a chromosome

AllelesAlleles

Different forms of a gene (back to Different forms of a gene (back to analogy…replacing jiffy p.b. with analogy…replacing jiffy p.b. with skippy p.b.) skippy p.b.)

DominantDominant allele (Uppercase allele (Uppercase letter) overrules a letter) overrules a recessiverecessive allele allele (lowercase letter) that it is paired (lowercase letter) that it is paired withwith

Allele CombinationsAllele Combinations

HomozygousHomozygous = =purebredpurebred having two identical alleles at a locushaving two identical alleles at a locus AA (dominant expressed)AA (dominant expressed) or or aa aa

(recessive expressed)(recessive expressed) HeterozygousHeterozygous = =hybridhybrid

having two different alleles at a locushaving two different alleles at a locus Aa (dominant expressed)Aa (dominant expressed)

Genotype & PhenotypeGenotype & Phenotype

Genotype refers to particular genes Genotype refers to particular genes an individual carriesan individual carries

Phenotype refers to an individual’s Phenotype refers to an individual’s observable traitsobservable traits

Cannot always determine genotype Cannot always determine genotype by observing phenotypeby observing phenotype

Tracking GenerationsTracking Generations

Parental generation Parental generation PPmates to produce mates to produce

First-generation offspring First-generation offspring FF11

mate to produce mate to produce

Second-generation offspring Second-generation offspring FF22

Earlobe Variation Earlobe Variation

Whether a person is born with Whether a person is born with attached or detached earlobes attached or detached earlobes depends on a single genedepends on a single gene

Gene has two molecular forms Gene has two molecular forms (alleles)(alleles)

Earlobe VariationEarlobe Variation

You inherited one allele for this gene You inherited one allele for this gene from each parentfrom each parent

Dominant allele specifies detached Dominant allele specifies detached earlobes (E)earlobes (E)

Recessive allele specifies attached Recessive allele specifies attached earlobes (e)earlobes (e)

Dominant & Recessive Dominant & Recessive AllelesAlleles

If you have attached earlobes, you If you have attached earlobes, you inherited two copies of the recessive inherited two copies of the recessive alleleallele

If you have detached earlobes, you If you have detached earlobes, you may have either one or two copies of may have either one or two copies of the dominant allelethe dominant allele

Early Ideas About Early Ideas About Heredity Heredity

People knew that sperm and People knew that sperm and eggs transmitted information eggs transmitted information about traitsabout traits

Blending theoryBlending theory Problem:Problem:

Would expect variation to Would expect variation to disappeardisappear

Variation in traits persistsVariation in traits persists

Gregor MendelGregor Mendel

Strong background Strong background in plant breeding in plant breeding and mathematicsand mathematics

Using pea plants, Using pea plants, found indirect but found indirect but observable evidence observable evidence of how parents of how parents transmit genes to transmit genes to offspringoffspring

Mendel was born in1822Mendel was born in1822 Austrian monkAustrian monk Studied at the Univ. of ViennaStudied at the Univ. of Vienna Teacher (High School)Teacher (High School)

FilamentAnther

StigmaStyle

Ovary

Carpel

PetalSepal

Ovule

Stamen

Section 24-1Figure 24–5 The Structure of a Flower

The Garden Pea PlantThe Garden Pea Plant

Self-pollinatingSelf-pollinating True breeding (different True breeding (different

alleles not normally alleles not normally introduced)introduced)

Can be experimentally cross-Can be experimentally cross-pollinatedpollinated

How did Mendel fertilize the

plants?

FF11 Results of One Results of One Monohybrid CrossMonohybrid Cross

F M

Dominant trait is

expressed

Recessive appears

Seed Shape

Flower Position

Seed CoatColor

Seed Color

Pod Color

Plant Height

PodShape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants

FF11 Results of Mendel’s Results of Mendel’s Dihybrid CrossesDihybrid Crosses

All plants displayed the dominant All plants displayed the dominant

form of both traits form of both traits

We now know:We now know:

All plants inherited one allele for each All plants inherited one allele for each

trait from each parenttrait from each parent

All plants were heterozygous (All plants were heterozygous (AaBbAaBb))

Principle of DominancePrinciple of Dominance

Some alleles are dominant and Some alleles are dominant and others are recessive.others are recessive.

Mendel wanted to know if the Mendel wanted to know if the recessive alleles disappeared or are recessive alleles disappeared or are they still in the f1,just hidden.they still in the f1,just hidden.

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Principles of Dominance

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Principles of Dominance

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Principles of Dominance

Mendel’s Theory Mendel’s Theory of Segregationof Segregation

An individual inherits a unit of An individual inherits a unit of information (allele) about a trait information (allele) about a trait from each parentfrom each parent

During gamete formation, the alleles During gamete formation, the alleles segregate from each other segregate from each other

Independent AssortmentIndependent Assortment

Mendel concluded that the two Mendel concluded that the two “units” for the first trait were to be “units” for the first trait were to be assorted into gametes independently assorted into gametes independently of the two “units” for the other traitof the two “units” for the other trait

Members of each pair of homologous Members of each pair of homologous chromosomes are sorted into chromosomes are sorted into gametes at random during meiosis gametes at random during meiosis

Independent AssortmentIndependent Assortment

Metaphase I

Metaphase II:

Gametes:

1/4 AB 1/4 ab 1/4 Ab 1/4 aB

A A A A

A A A A

AAAA

B B

B B

BB

B B

BBBB

a a a a

aa aa

aaaa

bb b b

bb b b

b b b b

OR

FF22 Results of Results of Monohybrid CrossMonohybrid Cross

Type of alleles

The physical characteristic

Impact of Mendel’s WorkImpact of Mendel’s Work

Mendel presented his results in Mendel presented his results in 18651865

Paper received little noticePaper received little notice Mendel discontinued his Mendel discontinued his

experiments in 1871experiments in 1871 Paper rediscovered in 1900 and Paper rediscovered in 1900 and

finally appreciated finally appreciated

ProbabilityProbability

The likelihood that a particular event The likelihood that a particular event will occur.will occur.

Flip a coin.Flip a coin. We use Punnett SquaresWe use Punnett Squares

D 38- Deduce the probable mode of D 38- Deduce the probable mode of inheritance of traits (e.g., inheritance of traits (e.g.,

Punnett Squares of Test Crosses

Homozygous recessive

a a

A

a aa

Aa Aa

aa

Homozygous recessive

a a

A

A Aa

Aa Aa

Aa

Two phenotypes All dominant phenotype

Punnett Square of a Punnett Square of a Monohybrid CrossMonohybrid Cross

Female gametes

Male gametes

A a

A

a Aa

AA Aa

aa

Dominant phenotype canarise 3 ways,recessive only one

Test CrossTest Cross

Individual that shows dominant Individual that shows dominant phenotype is crossed with individual phenotype is crossed with individual with recessive phenotypewith recessive phenotype

Examining offspring allows you to Examining offspring allows you to determine the genotype of the determine the genotype of the dominant individualdominant individual

Tt X Tt Cross

Tt X Tt Cross

Tt X Tt Cross

Genetics Practice Genetics Practice Problem 1Problem 1

What occurs when a purple plant What occurs when a purple plant that is heterozygous is fertilized by a that is heterozygous is fertilized by a white plant?white plant?

Identify generationsIdentify generations Punnett SquarePunnett Square Genotypes %Genotypes % Phenotype %Phenotype %

Principle of Independent Principle of Independent AssortmentAssortment

The genes for different traits The genes for different traits separate independently of one separate independently of one another during the formation of another during the formation of gametes.gametes.

Figure 11-10 Independent Assortment in Peas

Yellow round 9/16Yellow round 9/16 Green round 3/16Green round 3/16 Yellow wrinkled 3/16Yellow wrinkled 3/16 Green wrinkled 1/16Green wrinkled 1/16

9 : 3 : 3 : 1 Ratio9 : 3 : 3 : 1 Ratio

Dihybrid Cross Dihybrid Cross

Experimental cross between Experimental cross between individuals that are homozygous individuals that are homozygous

for different versions of for different versions of twotwo traits traits

Straight Thumb (Dominant)

Curved Thumb (Recessive)

Straight Pinky (Dominant)

Bent Pinky (Recessive)

More Dominant Traits

Polydactylism Achondroplastic Dwarfism

Tay-Sachs Disease - One Wrong Letter

Dominance Relations Dominance Relations

Complete dominance Complete dominance Incomplete dominanceIncomplete dominance

Heterozygote phenotype is somewhere Heterozygote phenotype is somewhere between that of two homozyotesbetween that of two homozyotes

CodominanceCodominance Non-identical alleles specify two Non-identical alleles specify two

phenotypes that are both expressed in phenotypes that are both expressed in heterozygotesheterozygotes

Flower Color in Flower Color in Snapdragons: Snapdragons:

Incomplete DominanceIncomplete Dominance

Red-flowered plant X White-flowered Red-flowered plant X White-flowered

plantplant

Pink-flowered Pink-flowered FF11 plants plants

(homozygote) (homozygote)

(heterozygotes)

Flower Color in Flower Color in Snapdragons: Incomplete Snapdragons: Incomplete

DominanceDominance Red flowers - two alleles allow them Red flowers - two alleles allow them

to make a red pigmentto make a red pigment White flowers - two mutant alleles; White flowers - two mutant alleles;

can’t make red pigmentcan’t make red pigment Pink flowers have one normal and Pink flowers have one normal and

one mutant allele; make a smaller one mutant allele; make a smaller amount of red pigmentamount of red pigment

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers

Figure 11-11 Incomplete Dominance in Four O’Clock Flowers

Flower Color in Flower Color in Snapdragons: Incomplete Snapdragons: Incomplete

DominanceDominance

Pink-flowered plant X Pink-flowered Pink-flowered plant X Pink-flowered

plantplant

White-, pink-, and red-flowered plants White-, pink-, and red-flowered plants in a 1:2:1 ratioin a 1:2:1 ratio

(heterozygote) (heterozygote)

Incomplete DominanceIncomplete Dominance

Neither allele is dominant

over the other

Combination of red and

white flowers

CodominantCodominant

Sickle Cell DiseaseSickle Cell Disease ABO Blood TypesABO Blood Types

Pleitropy Pleitropy

Alleles at a single locus may have Alleles at a single locus may have effects on two or more traitseffects on two or more traits

Classic example is the effects of the Classic example is the effects of the mutant allele at the beta-globin mutant allele at the beta-globin locus that gives rise to sickle-cell locus that gives rise to sickle-cell anemiaanemia

Teachers Domain - A Mutation Story

Genetics of Sickle-Cell Genetics of Sickle-Cell AnemiaAnemia

Two allelesTwo alleles1) 1) HbHbAA

Encodes normal beta hemoglobin Encodes normal beta hemoglobin chainchain

2) 2) HbHbSS

Mutant allele encodes defective Mutant allele encodes defective chainchain

HbHbSS homozygotes produce only the homozygotes produce only the defective hemoglobin; suffer from defective hemoglobin; suffer from sickle-cell anemiasickle-cell anemia

Pleiotrophic Effects of Pleiotrophic Effects of HbHbSS/Hb/HbSS

At low oxygen levels, cells with only At low oxygen levels, cells with only HbHbSS hemoglobin “sickle” and stick hemoglobin “sickle” and stick togethertogether

This impedes oxygen delivery and This impedes oxygen delivery and blood flowblood flow

Over time, it causes damage Over time, it causes damage throughout the bodythroughout the body

Blood TypingBlood Typing

Karl Landsteiner 1897Karl Landsteiner 1897 Worked at the Univ. of Vienna, Worked at the Univ. of Vienna,

Vienna Austria (Sound familiar?)Vienna Austria (Sound familiar?) Wanted to find out which red blood Wanted to find out which red blood

cells would clotcells would clot

First found two different groups, A First found two different groups, A and Band B

Third group would not clot when Third group would not clot when exposed to A or B What do you think exposed to A or B What do you think this was?this was?

What about the forth group?What about the forth group?

Genetics of ABO Blood Genetics of ABO Blood Types: Three AllelesTypes: Three Alleles

Gene that controls ABO type codes Gene that controls ABO type codes for enzyme that dictates structure of for enzyme that dictates structure of a glycolipid on blood cellsa glycolipid on blood cells

Two alleles (Two alleles (IIAA and and IIBB) are ) are codominant when pairedcodominant when paired

Third allele (Third allele (ii) is recessive to others) is recessive to others

ABO Blood Type:ABO Blood Type: Glycolipids on Red Cells Glycolipids on Red Cells

Type A - Glycolipid A on cell surfaceType A - Glycolipid A on cell surface

Type B - Glycolipid B on cell surfaceType B - Glycolipid B on cell surface

Type AB - Both glyocolipids A & BType AB - Both glyocolipids A & B

Type O - Neither glyocolipid A nor BType O - Neither glyocolipid A nor B

ABO Blood Type:ABO Blood Type:Allele CombinationsAllele Combinations

Type A - Type A - IIAAIIAA or or IIAAii

Type B - Type B - IIBBIIBB oror I IBBii

Type AB - Type AB - IIAAIIBB

Type O - Type O - iiii

ABO and TransfusionsABO and Transfusions

Recipient’s immune system will Recipient’s immune system will

attack blood cells that have an attack blood cells that have an

unfamiliar glycolipid on surfaceunfamiliar glycolipid on surface

Type O is universal donor because it Type O is universal donor because it

has neither type A nor type B has neither type A nor type B

glycolipidglycolipid

Codominance and Codominance and Multiple Alleles - AB or Multiple Alleles - AB or

NOT AB NOT AB

Codominance - both alleles are dominant

IA and IB

Multiple Alleles - genes have more than two alleles

IA, IB, Ia

Phenotype(Blood Type Genotype

Antigen on Red Blood Cell

Safe Transfusions

To From

Figure 14-4 Blood Groups

Universal Acceptor

Universal Donor

Rh factor - Another Rh factor - Another Blood TraitBlood Trait

Pregnancy complications Pregnancy complications Rh is a type of protein in the bloodRh is a type of protein in the blood If an Rh- man reproduces with an Rh If an Rh- man reproduces with an Rh

+ woman complications can occur.+ woman complications can occur.

Polygenic Traits: Polygenic Traits: Desiree’s Baby Case Desiree’s Baby Case

StudyStudy More than one gene controls a traitMore than one gene controls a trait Skin color more than one gene, Skin color more than one gene,

incomplete dominanceincomplete dominance

A,B and C are dark a,b and c are light

Sex Linked Traits - Sex Linked Traits - traits that are carried traits that are carried on the either the x or y on the either the x or y

chromosomechromosome

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Male

Female

Figure 14-13 Colorblindness

Father(normal vision)

ColorblindNormal vision

Mother (carrier)

Daughter(normal vision)

Son(normal vision)

Daughter(carrier)

Son(colorblind)

Male

Female

Figure 14-13 Colorblindness

ColorblindnessColorblindness

Cystic Fibrosis - Finding Cures is Hard

Sex-Linked DisorderSex-Linked Disorder

Male Pattern Baldness (X chromosome)

Hairy Pinna - long hair on ears

Chromosome # 7

CFTR gene

The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein.

Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane.

The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.

Figure 14-8 The Cause of Cystic Fibrosis

Recessive DisorderRecessive Disorder

AlbinismAlbinism

Phenotype results when pathway for Phenotype results when pathway for melanin production is completely melanin production is completely blockedblocked

Genotype - Homozygous recessive at Genotype - Homozygous recessive at the gene locus that codes for the gene locus that codes for tyrosinase, an enzyme in the tyrosinase, an enzyme in the melanin-synthesizing pathwaymelanin-synthesizing pathway

Human Genetics

Tracing Genes Through Tracing Genes Through Families - Human Families - Human

PedigreesPedigrees

Female

Male

Partner

Brothers and Sisters

A circle represents a female.

A square represents a male.

A horizontal line connecting a male and female represents a marriage.

A vertical line and a bracket connect the parents to their children.

A half-shaded circle or square indicates that a person is a carrier of the trait.

A completely shaded circle or square indicates that a person expresses the trait.

A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.

Figure 14-3 A Pedigree

Ability to roll the tongue in the Senator

Family

Tongue Roller - dominant, Non-Tongue Roller - recessive

White = tongue roller, Purple = non-roller

What are the genotypes of everyone? R = roller, r = non roller

George, Sam, Ann, Michael, Daniel and Alan are Rr

Arlene, Tom, Wilma, and Carla are rr

Sandra, Tina and Christopher are either RR or Rr

Case Study - Hemophilia Case Study - Hemophilia and the Royal Familyand the Royal Family

1. First, let’s take a look at Queen Victoria’s son Leopold’s family. His daughter, Alice of Athlone, had one hemophilic son (Rupert) and two other children—a boy and a girl—whose status is unknown. a) What is the probability that her other son was hemophilic? b) What is the probability that her daughter was a carrier? Hemophilic? c) What is the probability that both children were normal?

2. Now for the Spanish connection: Victoria’s youngest child, Beatrice, gave birth to one daughter, one normal son, and two hemophilic sons. Looking at the pedigree of the royal family, identify which of Beatrice’s children received the hemophilic gene; why can you make this conclusion? Notice that Beatrice’s daughter, Eugenie, married King Alfonso XIII of Spain and had six children, one of whom was the father of Juan Carlos, the current King of Spain. Would you predict that Juan Carlos was normal, a carrier, or a hemophilic?

3. Alexis did not die from hemophilia. At the age of fourteen he was executed with the rest of the family. His four oldest sisters were also young and didn’t have children, so we don’t know whether any of them was a carrier. But we can make an estimate. a) What are the probabilities that all four of the girls were carriers of the allele hemophilia? b) Supposing Alexis had lived and married a normal woman, what are the chances that his daughter would be a hemophiliac? c) What are the chances his daughters would be carriers? d) What are the chances that his sons would be hemophiliacs?

Homologous chromosomes fail to separate

Meiosis I:Nondisjunction

Meiosis II

Nondisjunction

Homologous chromosomes fail to separate

Meiosis I:Nondisjunction

Meiosis II

Nondisjunction

Homologous chromosomes fail to separate

Meiosis I:Nondisjunction

Meiosis II

Nondisjunction

Epistasis Epistasis

Interaction between the products of Interaction between the products of gene pairsgene pairs

Common among genes for hair color Common among genes for hair color in mammalsin mammals

Genetics of Coat Color Genetics of Coat Color in Labrador Retrieversin Labrador Retrievers

Two genes involvedTwo genes involved- One gene influences melanin - One gene influences melanin

productionproduction Two alleles -Two alleles - B B (black) is dominant over(black) is dominant over b b

(brown)(brown)

- Other gene influences melanin - Other gene influences melanin depositiondeposition Two alleles -Two alleles - E E promotes pigment promotes pigment

deposition and is dominant overdeposition and is dominant over e e

Allele Combinations Allele Combinations and Coat Color and Coat Color

Black coat - Must have at least one Black coat - Must have at least one

dominant allele at dominant allele at bothboth loci loci

BBEE, BbEe, BBEe,BBEE, BbEe, BBEe, or or BbEE BbEE

Brown coat - Brown coat - bbEE, bbEebbEE, bbEe

Yellow coat - Yellow coat - Bbee, BbEE, bbeeBbee, BbEE, bbee

Comb Shape in PoultryComb Shape in Poultry

Alleles at two loci (Alleles at two loci (RR and and PP) interact ) interact

Walnut comb - Walnut comb - RRPP, RRPp, RrPP, RrPpRRPP, RRPp, RrPP, RrPp Rose comb - Rose comb - RRpp, RrppRRpp, Rrpp Pea comb - Pea comb - rrPP, rrPprrPP, rrPp Single comb - Single comb - rrpprrpp

Campodactyly: Campodactyly: Unexpected Phenotypes Unexpected Phenotypes

Effect of allele varies:Effect of allele varies:

Bent fingers on both handsBent fingers on both hands

Bent fingers on one handBent fingers on one hand

No effectNo effect

Many factors affect gene expressionMany factors affect gene expression

Continuous VariationContinuous Variation

A more or less continuous range of A more or less continuous range of small differences in a given trait small differences in a given trait among individualsamong individuals

The greater the number of genes The greater the number of genes

and environmental factors that affect and environmental factors that affect

a trait, the more continuous the a trait, the more continuous the

variation in versions of that traitvariation in versions of that trait

Human VariationHuman Variation

Some human traits occur as a few Some human traits occur as a few discrete typesdiscrete types Attached or detached earlobes Attached or detached earlobes Many genetic disordersMany genetic disorders

Other traits show continuous Other traits show continuous variationvariation HeightHeight WeightWeight Eye colorEye color

Temperature Effects Temperature Effects on Phenotype on Phenotype

Himalayan rabbits are Himalayan rabbits are Homozygous for an Homozygous for an allele that specifies a allele that specifies a heat-sensitive version of heat-sensitive version of an enzyme in melanin-an enzyme in melanin-producing pathwayproducing pathway

Melanin is produced in Melanin is produced in cooler areas of bodycooler areas of body

Environmental Effects Environmental Effects on Plant Phenotypeon Plant Phenotype

Hydrangea macrophyllaHydrangea macrophylla

Action of gene responsible for floral Action of gene responsible for floral color is influenced by soil aciditycolor is influenced by soil acidity

Flower color ranges from pink to Flower color ranges from pink to blueblue