Chapter 9 1 Biology and Society: Our Longest …profwelday.weebly.com/uploads/2/3/0/0/23005790/lec_01-23_ch9.pdfIn an Abbey Garden • Mendel studied garden peas because they – were

© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko

PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and

Campbell Essential Biology with Physiology,

Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece

Chapter 9Chapter 9Patterns of Inheritance

1

• People have selected and mated dogs with

preferred traits for more than 15,000 years.

• Over thousands of years, such genetic tinkering

has led to the incredible variety of body types

and behaviors in dogs today.

• The biological principles underlying genetics

have only recently been understood.

Biology and Society: Our Longest-Running Genetic Experiment: Dogs

© 2013 Pearson Education, Inc.

2

Figure 9.0 3

• Heredity is the transmission of traits from one

generation to the next.

• Genetics is the scientific study of heredity.

• Gregor Mendel

– worked in the 1860s,

– was the first person to analyze patterns of inheritance, and

– deduced the fundamental principles of genetics.

HERITABLE VARIATION AND PATTERNS OF INHERITANCE


4

In an Abbey Garden

• Mendel studied garden peas because they

– were easy to grow,

– came in many readily distinguishable varieties,

– are easily manipulated, and

– can self-fertilize.


5 Figure 9.2

Carpel(produces eggs)

Stamen(makes sperm-producingpollen)

Petal

6

Figure 9.3-1

Removedstamensfrom purpleflower.

Stamens

Transferred pollen fromstamens of white flower

to carpel of purple flower.

Parents

(P)

Carpel

2

1

7 Figure 9.3-2


Stamens



Parents

(P)

Carpel

Pollinated carpel

matured into pod.

3

2

1

8

Figure 9.3-3


Stamens



Parents

(P)

Carpel

Offspring

(F1)

Pollinated carpel

matured into pod.

Planted seeds

from pod.

4

3

2

1

9

• A character is a heritable feature that varies

among individuals.

• A trait is a variant of a character.

• Each of the characters Mendel studied occurred in

two distinct traits.

In an Abbey Garden


10

• Mendel

– created purebred varieties of plants and

– crossed two different purebred varieties.

In an Abbey Garden


11

• Hybrids are the offspring of two different

purebred varieties.

– The parental plants are the P generation.

– Their hybrid offspring are the F1 generation.

– A cross of the F1 plants forms the F2 generation.

In an Abbey Garden


12

Mendel’s Law of Segregation

• Mendel performed many experiments.

• He tracked the inheritance of characters that occur

as two alternative traits.


13 Figure 9.4

WhitePurple

RecessiveDominant

Green Yellow

Terminal Axial

Wrinkled Round

Green Yellow

Seed shape

Seed color

Flower position

Flower color

Pod color

RecessiveDominant

Pod shape

Stem length

Inflated Constricted

Tall Dwarf

14

Figure 9.4a 15Monohybrid Crosses

• A monohybrid cross is a cross between purebred

parent plants that differ in only one character.


16

Figure 9.5-1

Purple flowers

White flowers

P Generation(purebredparents)

17 Figure 9.5-2

Purple flowers

F1 Generation

White flowers


All plants havepurple flowers

18

Figure 9.5-3

Purple flowers

F1 Generation

White flowers


All plants havepurple flowers

F2 Generation

Fertilizationamong F1 plants(F1 ×××× F1)

of plants

have purple flowers

of plants

have white flowers

34

14

19

• Mendel developed four hypotheses from the

monohybrid cross, listed here using modern

terminology (including “gene” instead of “heritable

factor”).

1. The alternative versions of genes are called alleles.

Monohybrid Crosses


20

2. For each inherited character, an organism inherits two alleles, one from each parent.

– An organism is homozygous for that gene if both

alleles are identical.

– An organism is heterozygous for that gene if the

alleles are different.

Monohybrid Crosses


21

3. If two alleles of an inherited pair differ,

– then one determines the organism’s appearance

and is called the dominant allele and

– the other has no noticeable effect on the organism’s

appearance and is called the recessive allele.

Monohybrid Crosses


22

4. Gametes carry only one allele for each inherited character.

– The two alleles for a character segregate (separate)

from each other during the production of gametes.

– This statement is called the law of segregation.

Monohybrid Crosses


23

• Do Mendel’s hypotheses account for the 3:1 ratio

he observed in the F2 generation?

• A Punnett square highlights

– the four possible combinations of gametes and

– the four possible offspring in the F2 generation.

Monohybrid Crosses


24

• Geneticists distinguish between an organism’s

physical appearance and its genetic makeup.

– An organism’s physical appearance is its phenotype.

– An organism’s genetic makeup is its genotype.

Monohybrid Crosses


25 Figure 9.6P Generation Genetic makeup (alleles)

Alleles carried by parents

Gametes

Purple flowersPP

White flowerspp

All P All p

pP

F1 Generation(hybrids)

F2 Generation(hybrids)

Allelessegregate

Gametes

Purple flowersAll Pp

21

21

Sperm fromF1 plant

Eggs fromF1 plant

Phenotypic ratio3 purple : 1 white

Genotypic ratio1 PP : 2 Pp : 1 pp

p

p

P

PPP Pp

Pp pp

26


Blast Animation: Single-Trait Crosses

Select “Play”

27 Genetic Alleles and Homologous Chromosomes

• A gene locus is a specific location of a gene along

a chromosome.

• Homologous chromosomes have alleles (alternate

versions) of a gene at the same locus.


28

Figure 9.7

Homologouschromosomes

P

Genotype:

Gene loci

P

a

aa

b

B

Dominantallele

Recessive allele

BbPP

Homozygousfor thedominant allele

Homozygousfor therecessive allele

Heterozygouswith one dominantand one recessiveallele

a

29 Mendel’s Law of Independent Assortment

• A dihybrid cross is the mating of parental

varieties differing in two characters.

• What would result from a dihybrid cross? Two

hypotheses are possible:

1. dependent assortment or

2. independent assortment.


30


Blast Animation: Two-Trait Crosses

Select “Play”

31 Figure 9.8

F1 Generation

F2 Generation

RRYY

Predicted results(not actually seen)

P Generation

Gametes RY

rryy

ry

(a) Hypothesis: Dependent assortment

RrYy

RY ry

Sperm

EggsEggs

RY

ry

Actual results(support hypothesis)

RRYY

RY

rryy

ry

RrYy

(b) Hypothesis: Independent assortment

Gametes

RY ry

Sperm

RY

ry

Ry

rY

RyrY

RRYY

RryyRRyyRrYyRRYy

RrYy rrYy Rryy rryy

RrYY

RrYY rrYY RrYy rrYy

RRYy RrYy

Yellowround

Yellowwrinkled

Greenwrinkled

Greenround

16

1

16

3

16

3

16

9

4

1

4

1

4

1

4

1

4

1

4

1

4

1

4

1

2

1

2

1

2

1

2

1

32

• Mendel’s dihybrid cross supported the hypothesis

that each pair of alleles segregates independently

of the other pairs during gamete formation.

• Thus, the inheritance of one character has no

effect on the inheritance of another.

• This is called Mendel’s law of independent assortment.

• Independent assortment is also seen in two

hereditary characters in Labrador retrievers.

Mendel’s Law of Independent Assortment


33 Figure 9.9Blind dog

Phenotypes

(a) Possible phenotypes of Labrador retrievers

B_N_

Blind dog

Genotypes

(b) A Labrador dihybrid cross

Black coat,

normal visionB_nn

Black coat,

blind (PRA)bbnn

Chocolate coat,blind (PRA)

bbN_

Chocolate coat,

normal vision

Mating of double heterozygotes

(black coat, normal vision)

BbNn BbNn

Phenotypicratio ofoffspring

9 black coat,

normal vision

3 black coat,

blind (PRA)

3 chocolate coat,

normal vision1 chocolate coat,

blind (PRA)

Blind Blind

34

Figure 9.9a

Blind

Blind

Mating of double hererozygotes(BbNn ×××× BbNn)

9 black coat,normal vision

3 black coat,blind (PRA)

3 chocolate coat,normal vision

1 chocolate coat,blind (PRA)

35 Using a Testcross to Determine an Unknown Genotype

• A testcross is a mating between

– an individual of dominant phenotype (but unknown genotype) and

– a homozygous recessive individual.


36

Figure 9.10

Two possible genotypes for the black dog:

B_ bb

Testcross

Genotypes

Bb

B b

orBB

B

b Bb Bb bbb

Gametes

Offspring All black 1 black : 1 chocolate

37 The Rules of Probability

• Mendel’s strong background in mathematics

helped him understand patterns of inheritance.

• The rule of multiplication states that the

probability of a compound event is the product of

the separate probabilities of the independent

events.


38

Figure 9.11

F1 Genotypes

F2 Genotypes

Bb female Bb male

Formation of eggs Formation of sperm

Malegametes

Fem

ale

gam

ete

s

2

1

2

1

2

1

2

1

2

1

2

14

1

4

1

4

1

4

1

( ×××× )

B

BB B B

B

b

b

b b b b

39 Family Pedigrees

• Mendel’s principles apply to the inheritance of

many human traits.


40

Figure 9.12

DO

MIN

AN

T T

RA

ITS

Free earlobe

RE

CE

SS

IVE

TR

AIT

S

Widow’s peakFreckles

Attached earlobeStraight hairlineNo freckles

41 Figure 9.12a

Freckles No freckles

42

Figure 9.12b

Widow’s peak Straight hairline

43 Figure 9.12c

Free earlobe Attached earlobe

44

• Dominant traits are not necessarily

– normal or

– more common.

• Wild-type traits are

– those seen most often in nature and

– not necessarily specified by dominant alleles.

Family Pedigrees


45

• A family pedigree

– shows the history of a trait in a family and

– allows geneticists to analyze human traits.

Family Pedigrees


46

Figure 9.13

Female Male

Attached Free

Female Male

First generation(grandparents)

Second generation(parents, aunts, anduncles)

Third generation(brother andsister)

AaronFf

BettyFf

Cletusff

DebraFf

EvelynFForFf

LisaFForFf

Fredff

Gabeff

HalFf

InaFf

Jillff

Kevinff

50 Human Disorders Controlled by a Single Gene

• Many human traits

– show simple inheritance patterns and

– are controlled by single genes on autosomes.


51

Table 9.1 52 Recessive Disorders

• Most human genetic disorders are recessive.

• Individuals who have the recessive allele but

appear normal are carriers of the disorder.


53

Figure 9.14

Parents

Offspring

DdHearing Hearing

Dd

Sperm

Eggs

D

HearingD

Dd

d

Hearing

(carrier)

DD

DdHearing

(carrier)

dd

Deafd

54

• Cystic fibrosis is

– the most common lethal genetic disease in the United States and

– caused by a recessive allele carried by about one in 31 Americans.

Recessive Disorders


55

• Prolonged geographic isolation of certain

populations can lead to inbreeding, the mating of

close relatives.

• Inbreeding increases the chance of offspring that

are homozygous for a harmful recessive trait.

Recessive Disorders


56 Dominant Disorders

• Some human genetic disorders are dominant.

– Achondroplasia is a form of dwarfism.

– The homozygous dominant genotype causes

death of the embryo.

– Thus, only heterozygotes have this disorder.

– Huntington’s disease, which leads to degeneration of the nervous system, does not usually begin until middle age.


57

Figure 9.15 58 Figure 9.16

Parents

Sperm

Eggs

d

DwarfD

Dd

d

Dd

ddd

Normal

(no achondroplasia) Molly JoDwarf

(achondroplasia)Dddd

Normaldd

Normal

DwarfMatt AmyJacob Zachary

Jeremy

59

Genetic Testing

• Today many tests can detect the presence of

disease-causing alleles.

• Most genetic tests are performed during

pregnancy.

– Amniocentesis collects cells from amniotic fluid.

– Chorionic villus sampling removes cells from placental tissue.

• Genetic counseling helps patients understand the

results and implications of genetic testing.


60

Documents

Chapter 9 1 Biology and Society: Our Longest …profwelday.weebly.com/uploads/2/3/0/0/23005790/lec_01-23_ch9.pdfIn an Abbey Garden • Mendel studied garden peas because they – were