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BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 9
Patterns of Inheritance
Modules 9.1 – 9.10
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Purebreds and Mutts — A Difference of Heredity
• Genetics is the science of heredity
• These black Labrador puppies are purebred—
their parents and grandparents were black Labs
with very similar genetic makeups
– Purebreds
often suffer
from serious
genetic defects
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The parents of these puppies were a mixture of
different breeds
– Their behavior
and appearance
is more varied
as a result of
their diverse
genetic
inheritance
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
MENDEL’S PRINCIPLES
9.1 The science of genetics has ancient roots
• The science of heredity dates back to ancient
attempts at selective breeding
• Until the 20th century, however, many
biologists erroneously believed that
– characteristics acquired during lifetime could be
passed on
– characteristics of both parents blended
irreversibly in their offspring
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9.2 Experimental genetics began in an abbey
garden
• Modern genetics began with Gregor Mendel’s
quantitative experiments with pea plants
Stamen
Carpel
Figure 9.2A, B
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• Mendel crossed
pea plants that
differed in certain
characteristics and
traced the traits
from generation to
generation
• This illustration
shows his
technique for
cross-fertilization
White
1
Removed
stamens
from purple
flower
Stamens
Carpel
PARENTS
(P)
2 Transferred
Purple
pollen from
stamens of white
flower to carpel
of purple flower
3 Pollinated carpel
matured into pod
4
OFFSPRING
(F1)
Figure 9.2C
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Planted
seeds
from pod
• Mendel studied
seven pea
characteristics
FLOWER
COLOR
Purple
White
Axial
Terminal
SEED
COLOR
Yellow
Green
SEED
SHAPE
Round
Wrinkled
POD
SHAPE
Inflated
Constricted
POD
COLOR
Green
Yellow
STEM
LENGTH
Tall
Dwarf
FLOWER
POSITION
• He hypothesized
that there are
alternative forms
of genes
(although he did
not use that
term), the units
that determine
heredity
Figure 9.2D
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9.3 Mendel’s principle of segregation describes the
inheritance of a single characteristic
• From his
experimental data,
Mendel deduced
that an organism
has two genes
(alleles) for each
inherited
characteristic
– One characteristic
comes from each
parent
Figure 9.3A
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P GENERATION
(true-breeding
parents)
Purple flowers
White flowers
All plants have
purple flowers
F1
generation
Fertilization
among F1
plants
(F1 x F1)
F2
generation
3/
of plants
have purple flowers
4
1/
4 of plants
have white flowers
GENETIC MAKEUP (ALLELES)
• A sperm or egg
carries only one
allele of each pair
P PLANTS
Gametes
– The pairs of alleles
separate when
gametes form
PP
pp
All P
All p
F1 PLANTS
(hybrids)
Gametes
– This process
describes Mendel’s
law of segregation
All Pp
1/
2
1/
P
P
2
p
P
Eggs
Sperm
PP
F2 PLANTS
– Alleles can be
dominant or
recessive
Phenotypic ratio
3 purple : 1 white
p
p
Pp
Pp
pp
Genotypic ratio
1 PP : 2 Pp : 1 pp
Figure 9.3B
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9.4 Homologous chromosomes bear the two alleles
for each characteristic
• Alternative forms of a gene (alleles) reside at
the same locus on homologous chromosomes
GENE LOCI
P
P
a
a
B
DOMINANT
allele
b
RECESSIVE
allele
GENOTYPE:
PP
aa
HOMOZYGOUS
for the
dominant allele
HOMOZYGOUS
for the
recessive allele
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Bb
HETEROZYGOUS
Figure 9.4
9.5 The principle of independent assortment is
revealed by tracking two characteristics at
once
• By looking at two characteristics at once,
Mendel found that the alleles of a pair
segregate independently of other allele pairs
during gamete formation
– This is known as the principle of independent
assortment
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HYPOTHESIS:
DEPENDENT ASSORTMENT
RRYY
P
GENERATION
rryy
Gametes
RRYY
ry
RY
rryy
Gametes
ry
RY
RrYy
F1
GENERATION
Eggs
1/
HYPOTHESIS:
INDEPENDENT ASSORTMENT
2
1/
2
RY
1/
2
RrYy
RY
1/
ry
Sperm
2
1/
ry
1/
F2
GENERATION
1/
Eggs
1/
4
4
4
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RY
1/
4
RrYy
rY
1/
RrYY
rrYY
rrYy
Figure 9.5A
4
RRYY
RRYy
ACTUAL
RESULTS
SUPPORT
HYPOTHESIS
1/
RrYY
RrYy
Actual results
contradict
hypothesis
RY
rY
Ry
ry
4
RrYy
RrYy
RRyy
Rryy
rryy
Ry
1/
RrYy
rrYy
Rryy
4
4
ry
9/
16
3/
16
3/
16
1/
16
Yellow
round
Green
round
Yellow
wrinkled
Yellow
wrinkled
• Independent assortment of two genes in the
Labrador retriever
Blind
PHENOTYPES
GENOTYPES
Black coat,
normal vision
B_N_
Black coat,
blind (PRA)
B_nn
MATING OF HETEROZYOTES
(black, normal vision)
PHENOTYPIC RATIO
OF OFFSPRING
9 black coat,
normal vision
BbNn
3 black coat,
blind (PRA)
Figure 9.5B
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Blind
Chocolate coat,
normal vision
bbN_
Chocolate coat,
blind (PRA)
bbnn
BbNn
3 chocolate coat,
normal vision
1 chocolate coat,
blind (PRA)
9.6 Geneticists use the testcross to determine
unknown genotypes
• The offspring of a testcross often reveal the
genotype of an individual when it is unknown
TESTCROSS:
GENOTYPES
B_
bb
Two possibilities for the black dog:
BB
b
OFFSPRING
Bb
B
GAMETES
Figure 9.6
or
Bb
All black
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B
b
Bb
b
bb
1 black : 1 chocolate
9.7 Mendel’s principles reflect the rules of
probability
• Inheritance follows
the rules of probability
– The rule of
multiplication and
the rule of addition
can be used to
determine the
probability of certain
events occurring
F1 GENOTYPES
Bb female
Bb male
Formation of eggs
Formation of sperm
1/
B
1/
2
B
2
B
B
1/
b
1/
1/
2
b
B
b
1/
4
b
b
4
B
1/
2
4
b
F2 GENOTYPES
1/
4
Figure 9.7
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
9.8 Connection: Genetic traits in humans can be
tracked through family pedigrees
• The inheritance of many
human traits follows
Mendel’s principles and
the rules of probability
Figure 9.8A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Family pedigrees are used to determine
patterns of inheritance and individual
genotypes
Dd
Joshua
Lambert
Dd
Abigail
Linnell
D_?
Abigail
Lambert
D_?
John
Eddy
dd
Jonathan
Lambert
Dd
Dd
dd
D_?
Hepzibah
Daggett
Dd
Elizabeth
Eddy
Dd
Dd
Dd
dd
Female Male
Deaf
Figure 9.8B
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Hearing
9.9 Connection: Many inherited disorders in
humans are controlled by a single gene
• Most such
disorders are
caused by
autosomal
recessive alleles
– Examples:
cystic fibrosis,
sickle-cell
disease
Normal
Dd
PARENTS
Normal
Dd
D
D
Eggs
Sperm
DD
Normal
d
OFFSPRING
d
Dd
Normal
(carrier)
Dd
Normal
(carrier)
dd
Deaf
Figure 9.9A
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• A few are caused by dominant alleles
– Examples: achondroplasia, Huntington’s disease
Figure 9.9B
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Table 9.9
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9.10 Connection: Fetal testing can spot many
inherited disorders early in pregnancy
• Karyotyping and biochemical tests of fetal cells
and molecules can help people make
reproductive decisions
– Fetal cells can be obtained through
amniocentesis
Amniotic
fluid
Amniotic
fluid
withdrawn
Centrifugation
Fluid
Fetal
cells
Fetus
(14-20
weeks)
Biochemical
tests
Placenta
Figure 9.10A
Uterus
Cervix
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Several
weeks later
Cell culture
Karyotyping
• Chorionic villus sampling is another procedure
that obtains fetal cells for karyotyping
Fetus
(10-12
weeks)
Several hours
later
Placenta
Suction
Chorionic villi
Fetal cells
(from chorionic villi)
Karyotyping
Some
biochemical
tests
Figure 9.10B
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• Examination of the fetus with ultrasound is
another helpful technique
Figure 9.10C, D
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings