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powerlecture chapter 11

PowerLecture:Chapter 11

Observing Patterns in Inherited Traits

section 11 0 weblinks and infotrac
Section 11.0: Weblinks and InfoTrac

See the latest Weblinks and InfoTrac articles for this chapter online

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Videos: CNN

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  • Biology, 2003, Vol. 7. Tastier Tomatoes (2:53)
impacts issues in pursuit of a better rose
Impacts, Issues: In Pursuit of a Better Rose
  • Roses have been around for at least 40 million years
  • Researchers are working to create genetic maps for rose chromosomes
impacts issues in pursuit of a better rose7
Impacts, Issues: In Pursuit of a Better Rose
  • Knowing the location of desirable genes on chromosomes helps rose breeders mix the beauty of cultivated varieties with disease resistance of wild varieties
section 11 1 weblinks and infotrac
Section 11.1: Weblinks and InfoTrac

See the latest Weblinks and InfoTrac articles for this chapter online

earlobe variation
Earlobe Variation
  • Whether a person has attached or detached earlobes depends on a single gene
  • Attached earlobes: two copies of the recessive allele for this gene
  • Detached earlobes: either one or two copies of the dominant allele
early ideas about heredity
Early Ideas about Heredity
  • People knew that sperm and eggs transmitted information about traits
  • Blending theory
  • Problem:
    • Would expect variation to disappear
    • Variation in traits persists
gregor mendel
Gregor Mendel
  • Strong background in plant breeding and mathematics
  • Using pea plants, found indirect but observable evidence of how parents transmit genes to offspring
gregor mendel12
Gregor Mendel
  • The founder of modern genetics

Fig. 11-2, p.170

slide13
a Garden pea flower, cut in half. Sperm form in pollen grains, which originate in male floral parts

(stamens). Eggs develop, fertilization takes place, and seeds mature in female floral parts (carpels).

b Pollen from a plant that breeds true for purple flowers is brushed onto a floral bud of a plant that breeds true for white flowers. The white flower had its stamens snipped off. This is one way to assure cross-fertilization of plants.

c Later, seeds develop inside pods of the cross-fertilized plant. An embryo within each seed develops into a mature pea plant.

d Each new plant’s flower color is indirect but observable evidence that hereditary material has been transmitted from the parent plants.

Fig. 11-3, p.170

gregor mendel14
Gregor Mendel

Crossing garden pea plants

genes
Genes
  • Units of information about specific traits
  • Passed from parents to offspring
  • Each has a specific location (locus) on a chromosome
alleles
Alleles
  • Different molecular forms of a gene
  • Arise by mutation
  • Dominant allele masks a recessive allele that is paired with it
allele combinations
Allele Combinations
  • Homozygous
    • having two identical alleles at a locus
    • AA or aa
  • Heterozygous
    • having two different alleles at a locus
    • Aa
genetic terms
Genetic Terms

A pair of homologous chromosomes

A gene locus

A pair of alleles

Three pairs of genes

Figure 11.4Page 171

slide19
A pair of homologous chromosomes, each in the unduplicated state (most often, one from a male parent and its partner from a female parent)

A gene locus (plural, loci), the location for a specific gene on a chromosome. Alleles are at corresponding loci on a pair of homologous chromosomes

A pair of alleles may be identical or nonidentical. They are represented in the text by letters such as D or d

Three pairs of genes (at three loci on this pair of homologous chromosomes); same thing as three pairs of alleles

Fig. 11-4, p.171

genetic terms20
Genetic Terms

Genetic terms

genotype phenotype
Genotype & Phenotype
  • Genotype refers to particular genes an individual carries
  • Phenotype refers to an individual’s observable traits
  • Cannot always determine genotype by observing phenotype
section 11 2 weblinks and infotrac
Section 11.2: Weblinks and InfoTrac

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tracking generations
Tracking Generations
  • Parental generation P

mates to produce

  • First-generation offspring F1

mate to produce

  • Second-generation offspring F2
monohybrid crosses
Monohybrid Crosses

Experimental intercross between

two F1 heterozygotes

AA X aa

Aa (F1 monohybrids)

Aa X Aa

?

mendel s monohybrid cross results
Mendel’s Monohybrid Cross Results

5,474 round

1,850 wrinkled

6,022 yellow

2,001 green

882 inflated

299 wrinkled

428 green

152 yellow

F2 plants showed dominant-to-recessive ratio that averaged 3:1

705 purple

224 white

651 long stem

207 at tip

787 tall

277 dwarf

Fig. 11-6, p. 172

slide26
Trait Studied

Dominant Form

Recessive Form

F2 Dominant-to- Recessive Ratio

SEED SHAPE

5,474 round

1,850 wrinkled

2.96:1

SEED COLOR

6,022 yellow

2,001 green

3.01:1

POD SHAPE

882 inflated

299 wrinkled

2.95:1

POD COLOR

428 green

152 yellow

2.82:1

FLOWER COLOR

705 purple

224 white

3.15:1

FLOWER POSITION

651 long stem

207 at tip

3.14:1

STEM LENGTH

787 tall

277 dwarf

2.84:1

Fig. 11-6, p.172

probability
Probability

The chance that each outcome of a given event will occur is proportional to the number of ways that event can be reached

monohybrid cross illustrated
True-breeding

homozygous recessive

parent plant

F1PHENOTYPES

aa

True-breeding

homozygous dominant

parent plant

Aa

Aa

a

a

Aa

Aa

A

AA

A

Aa

Aa

Aa

Aa

An F1 plant

self-fertilizes

and produces

gametes:

F2PHENOTYPES

Aa

AA

Aa

A

a

A

AA

Aa

a

Aa

aa

Aa

aa

Monohybrid CrossIllustrated

Figure 11.7Page 173

mendel s theory of segregation
Mendel’s Theory of Segregation
  • An individual inherits a unit of information (allele) about a trait from each parent
  • During gamete formation, the alleles segregate from each other
slide33
Homozygous dominant parent

Homozygous recessive parent

Mendel’s Theory of Segregation

(chromosomes duplicated before meiosis)

meiosis I

meiosis II

(gametes)

(gametes)

fertilization produces heterozygous offspring

Fig. 11-5, p.172

test cross
Test Cross
  • Individual that shows dominant phenotype is crossed with individual with recessive phenotype
  • Examining offspring allows you to determine the genotype of the dominant individual
slide35
Homozygous

recessive

Homozygous

recessive

a a

a a

A

A

Aa

Aa

Aa

Aa

a

A

aa

Aa

aa

Aa

Punnett Squares of Test Crosses

Two phenotypes

All dominant phenotype

slide36
Punnett Squares of Test Crosses

POSSIBLE EVENT:

PROBABLE OUTCOME:

sperm A meets egg A

sperm A meets egg a

sperm a meets egg A

sperm a meets egg a

1/4 AA offspring

1/4 Aa

1/4 Aa

1/4 aa

p.173

slide37
aa

Aa

aa

a

A

a

A

A

a

A

a

A

A

A

A

Aa

AA

Aa

a

a

a

a

Aa

aa

Aa

aa

Punnett Squares of Test Crosses

female gametes

male gametes

Fig. 11-7a, p.173

slide38
female gametes

male gametes

Aa

aa

a

A

a

A

A

a

A

a

Aa

AA

Aa

A

A

A

A

a

aa

Aa

aa

Aa

aa

a

a

a

Punnett Squares of Test Crosses

Stepped Art

Fig. 11-7a, p.173

slide39
Punnett Squares of Test Crosses

True-breeding

homozygous recessive

parent plant

F1 PHENOTYPES

aa

True-breeding

homozygous dominant

parent plant

Aa

Aa

a

a

Aa

Aa

A

AA

Aa

Aa

A

Aa

Aa

Fig. 11-7b1, p.173

slide40
Punnett Squares of Test Crosses

An F1 plant self-fertilizes

and produces gametes:

F2 PHENOTYPES

Aa

AA

Aa

A

a

AA

Aa

A

Aa

aa

a

Aa

aa

Fig. 11-7b2, p.173

section 11 3 weblinks and infotrac
Section 11.3: Weblinks and InfoTrac

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dihybrid cross
Dihybrid Cross

Experimental cross between individuals that are homozygous for different versions of two traits

dihybrid cross f 1 results
Dihybrid Cross: F1 Results

purple

flowers, tall

white

flowers,

dwarf

TRUE-

BREEDING

PARENTS:

AABB

x

aabb

GAMETES:

AB

AB

ab

ab

AaBb

F1 HYBRID

OFFSPRING:

All purple-flowered, tall

dihybrid cross f 2 results
Dihybrid Cross: F2 Results

X

AaBb

AaBb

1/4 AB

1/4 Ab

1/4 aB

1/4 ab

9/16 purple-flowered, tall

1/4 AB

1/16

AABB

1/16

AABb

1/16

AaBB

1/16

AaBb

3/16 purple-flowered, dwarf

3/16 white-flowered, tall

1/16

AaBb

1/16

AAbb

1/16

Aabb

1/4 Ab

1/16

AABb

1/16 white-flowered, dwarf

1/16

AaBB

1/16

aaBB

1/16

aaBb

1/4 aB

1/16

AaBb

1/16

Aabb

1/16

aaBb

1/16

aabb

1/16

AaBb

1/4 ab

slide45
AABB

purple-

flowered

tall parent

(homozygous

dominant)

aabb

white-

flowered

dwarf parent

(homozygous

recessive)

X

AB

ab

F1 OUTCOME:

All of the F1 plants are AaBb heterozygotes

(purple flowers, tall stems).

AaBb

Fig. 11-9a, p.175

slide46
1/4

1/4

1/4

1/4

meiosis,

gamete

formation

AB

Ab

aB

ab

1/4

1/16

1/16

1/16

1/16

AABB

AABb

AaBB

AaBb

AB

1/4

1/16

1/16

1/16

1/16

Ab

AABb

AAbb

AaBb

Aabb

1/16

1/16

1/16

1/16

AaBB

AaBb

aaBB

aaBb

aB

1/16

1/16

1/16

1/16

1/4

AaBb

Aabb

aaBb

aabb

ab

Fig. 11-9b, p.175

independent assortment
Independent Assortment
  • Mendel concluded that the two “units” for the first trait were to be assorted into gametes independently of the two “units” for the other trait
  • Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis
independent assortment49
Independent Assortment

Metaphase I:

OR

A

A

a

a

A

A

a

a

B

B

b

b

b

b

B

B

Metaphase II:

A

A

a

a

A

A

a

a

B

B

b

b

b

b

B

B

Gametes:

B

B

b

b

b

b

B

B

A

A

a

a

A

A

a

a

1/4 AB

1/4 ab

1/4 Ab

1/4 aB

slide50
Independent Assortment

Nucleus of a

diploid (2n)

reproductive cell

with two pairs of

homologous

chromosomes

Possible alignments

of the two homologous

chromosomes during

metaphase I of meiosis

The resulting alignments

at metaphase II

Allelic combinations

possible in gametes

1/4 AB

1/4 ab

1/4 Ab

1/4 aB

Fig. 11-8, p.174

tremendous variation
Tremendous Variation

Number of genotypes possible in offspring as a result of independent assortment and hybrid crossing is

3n

(n is the number of gene loci at which the parents differ)

impact of mendel s work
Impact of Mendel’s Work
  • Mendel presented his results in 1865
  • Paper received little notice
  • Mendel discontinued his experiments in 1871
  • Paper rediscovered in 1900
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Section 11.4: Weblinks and InfoTrac

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dominance relations
Dominance Relations

Complete dominance

Incomplete dominance

Codominance

incomplete dominance
Incomplete

Dominance

Incomplete Dominance

X

Homozygous

parent

Homozygous

parent

All F1 are

heterozygous

X

F2 shows three phenotypes in 1:2:1 ratio

abo blood type
ABO Blood Type

Codominance: ABO blood types

slide57
Incomplete Dominance

homozygous parent

X

homozygous parent

All F1 offspring heterozygous for flower color:

Cross two of the F1 plants and the F2 offspring will show three phenotypes in a 1:2:1 ratio:

Fig. 11-11, p.176

incomplete dominance58
Incomplete Dominance

Incomplete dominance

codominance abo blood types
Codominance: ABO Blood Types
  • Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells
  • Two alleles (IA and IB) are codominant when paired
  • Third allele (i) is recessive to others
slide60
ABO Blood Type

Range of genotypes:

IAIA

IBIB

or

or

IAi

IAIB

IBi

ii

Blood

Types:

A

AB

B

O

Fig. 11-10a, p.176

slide61
ABO Blood Type

Fig. 11-10b, p.176

abo and transfusions
ABO and Transfusions
  • Recipient’s immune system will attack blood cells that have an unfamiliar glycolipid on surface
  • Type O is universal donor because it has neither type A nor type B glycolipid
pleiotropy
Pleiotropy
  • Alleles at a single locus may have effects on two or more traits
  • Marfan syndrome - Mutation in gene for fibrillin affects skeleton, cardiovascular system, lungs, eyes, and skin
pleiotropy64
Pleiotropy

Pleiotropic effects of Marfan syndrome

epistasis
Epistasis
  • Interaction between the products of gene pairs
  • Common among genes for hair color in mammals
epistasis66
Epistasis

Fig. 11-13, p.177

coat color in retrievers
Coat Color inRetrievers

BBEE

X

bbee

F1puppies

are all BbEe

F2puppies

BE

Be

bE

be

BE

black

BBEE

BBEe

BbEE

BbEe

Be

BBee

BbEe

Bbee

BBEe

brown

bE

BbEe

bbEE

bbEe

BbEE

yellow

be

Bbee

bbEe

bbee

BbEe

coat color in retrievers68
Coat Color in Retrievers

Coat color in Labrador retrievers

comb shape in poultry
Comb Shape in Poultry

RRpp

(rose comb)

rrPP

(pea comb)

P:

X

RrPp (all walnut comb)

F1:

F2:

9/16 walnut

3/16 rose

3/16 pea

1/16 single

rrpp

rrPP

rrPp

RRpp

Rrpp

RRPP

RRPp

RrPP

RrPp

slide70
Comb Shape in Poultry

rose comb

pea comb

walnut comb

single comb

X

rose

RRpp

pea

rrPP

F1

all walnut

RrPp

RrPp

RrPp

F2

9/16 walnut

RRPP, RRPp,RrPP, or RrPp

3/16 rose

RRpp or Rrpp

3/16 pea

rrPP or rrPp

1/16 single

rrpp

Fig. 11-12, p.177

comb shape in poultry71
Comb Shape in Poultry

Comb shape in chickens

coat color
Coat Color

Coat color in the Himalayan rabbit

section 11 5 weblinks and infotrac
Section 11.5: Weblinks and InfoTrac

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crossing over
Crossing Over
  • Each chromosome becomes zippered to its homologue
  • All four chromatids are closely aligned
  • Nonsister chromosomes exchange segments
effect of crossing over
Effect of Crossing Over
  • After crossing over, each chromosome contains both maternal and paternal segments
  • Creates new allele combinations in offspring
linkage groups
Linkage Groups
  • Genes on one type of chromosome
  • Fruit flies
    • 4 homologous chromosomes
    • 4 linkage groups
  • Not all genes on chromosome are tightly linked
full linkage
A

A

a

B

B

b

A

a

B

b

a

b

Full Linkage

x

Parents:

AB

ab

F1 offspring:

All AaBb

meiosis, gamete formation

Equal ratios of two types of gametes:

Figure 11.15Page 178

50% AB

50% ab

incomplete linkage
A

a

a

c

c

C

A

C

Incomplete Linkage

AC

ac

x

Parents:

F1 offspring:

All AaCc

meiosis, gamete formation

a

a

A

A

Unequal ratios of four types of gametes:

C

c

C

c

parental

genotypes

recombinant

genotypes

Figure 11.15Page 178

crossover frequency
Crossover Frequency

Proportional to the distance that separates genes

A

B

C

D

Crossing over will disrupt linkage between A and B more often than C and D

In-text figurePage 178

linkage mapping in humans
Linkage Mapping in Humans
  • Linkage maps based on pedigree analysis through generations
  • Color blindness and hemophilia are very closely linked on X chromosome
crossing over82
Crossing Over

Crossover review

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Section 11.6: Weblinks and InfoTrac

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videos cnn84
Videos: CNN

Ask your Thomson Sales Representative for these volumes on CD or VHS

  • Anatomy and Physiology, 2002, Vol. 6,Trigger for Parkinson’s (2:44)
environmental effects on plant phenotype
Environmental Effects on Plant Phenotype
  • Hydrangea macrophylla
  • Action of gene responsible for floral color is influenced by soil acidity
  • Flower color ranges from pink to blue
temperature effects on phenotype
Temperature Effects on Phenotype
  • Rabbit is homozygous for an allele that specifies a heat-sensitive version of an enzyme in melanin-producing pathway
  • Melanin is produced in cooler areas of body

Figure 11.16Page 179

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campodactyly unexpected phenotypes
Campodactyly: Unexpected Phenotypes
  • Effect of allele varies:
    • Bent fingers on both hands
    • Bent fingers on one hand
    • No effect
  • Many factors affect gene expression
continuous variation
Continuous Variation
  • A more or less continuous range of small differences in a given trait among individuals
  • The greater the number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait
human variation
Human Variation
  • Some human traits occur as a few discrete types
    • Attached or detached earlobes
    • Many genetic disorders
  • Other traits show continuous variation
    • Height
    • Weight
    • Eye color
slide94
Continuous Variation
  • Variation in human eye color

Fig. 11-18, p.180

describing continuous variation
(line of bell-shaped curve indicates continuous variation in population)

Number of individuals with

some value of the trait

Number of individuals with

some value of the trait

Range of values for the trait

Range of values for the trait

Describing Continuous Variation
slide96
Describing Continuous Variation

The line of a bell-shaped curve reveals

continuous variation in the population

Number of individuals with

some value of the trait

Range of values for the trait

Fig. 11-19a, p.180

slide97
Describing Continuous Variation

Number of individuals with

some value of the trait

Range of values for the trait

Fig. 11-19b, p.180

continuous variation99
Continuous Variation

Continuous variation in height

slide100
A

a

AA (dominant)

A

AA

Aa

Aa (dominant)

The expected

phenotypic

ratio of 3:1

Aa (dominant)

a

Aa

aa

aa (recessive)

p.182

slide102
dominant

recessive

Fig. 11-22, p.183

slide103
dominant

recessive

Fig. 11-22, p.183