Download Mendelian Genetics

Chapter 9
Patterns of Inheritance
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Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Unnumbered Figure p. 152
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Unnumbered Figure p. 153
A litter of puppies
of mixed ancestry
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Figure 9.2A Gregor Mendel in his garden
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Figure 9.2B Anatomy of a garden pea flower
Petal
Stamen
Carpel
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Figure 9.2C Mendel’s technique for
cross-fertilization of pea plants
1 Removed stamens
from purple
flower
White
Stamens
Carpel
Parents
(P)
2 Transferred pollen
from stamens of
Purple
white flower to
carpel of purple flower
3 Pollinated carpel
matured into pod
4 Planted seeds
from pod
Offspring
(F1)
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Figure 9.2D The seven pea characteristics studied by Mendel
Flower color
Purple
White
Flower position
Axial
Terminal
Seed color
Yellow
Green
Seed shape
Round
Wrinkled
Pod shape
Inflated
Pod color
Green
Stem length
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Tall
Constricted
Yellow
Dwarf
Figure 9.3A Crosses tracking one characteristic (flower color)
P generation
(true-breeding
parents)

Purple flowers
White flowers
All plants have
purple flowers
F1 generation
Fertilization
among F1 plants
(F1  F1)
F2 generation
3
4
1
of plants
of plants
4
have purple flowers have white flowers
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Figure 9.3B Explanation of the crosses in Figure 9.3A
P plants
Genetic makeup (alleles)
pp
PP
Gametes
All p
All P
F1 plants
(hybrids)
All Pp
Gametes
1
p
2
1
p
4
Sperm
F2 plants Phenotypic ratio
3 purple : 1 white
Eggs
Genotypic ratio
1 PP : 2 Pp : 1 pp
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P
p
P
PP
Pp
p
Pp
pp
Figure 9.4 Homologous chromosomes
Dominant
allele
Gene loci
Genotype:
P
a
B
P
a
b
PP
Homozygous
for the
dominant allele
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Recessive
allele
aa
Homozygous
for the
recessive allele
Bb
Heterozygous
Figure 9.5A Two hypotheses for segregation in a
dihybrid cross
Hypothesis: Dependent assortment
RRYY
Hypothesis: Independent assortment
rryy
RRYY
rryy
P generation
Gametes RY
X
ry
Gametes RY
RrYy
F1 generation
RrYy
Sperm
Sperm
1
2
RY
1
2
1
1
rY
RY
4
4
ry
1
RY
2
Eggs
F2 generation
ry
X
1
2
ry
1
4
RY
1
4
rY
Eggs
Actual results
contradict hypothesis
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1
4
Ry
1
4
ry
1
4
Ry
RRYY
RyYY
RRYy
RrYY
rrYY
RrYy
1
4
ry
RrYy
rrYy
RRYy
RrYy
RRyy
Rryy
RrYy
rrYy
Rryy
rryy
Actual results
support hypothesis
9
16
3
16
3
16
1
16
Yellow
round
Green
round
Yellow
wrinkled
Green
wrinkled
Figure 9.5B Independent assortment of two genes
in the Labrador retriever
Blind
Blind
Phenotypes
Genotypes
Black coat, normal vision
B_N_
Black coat, blind (PRA) Chocolate coat, normal vision Chocolate coat, blind (PRA)
B_nn
bbN_
bbnn
Mating of heterozygotes
(black, normal vision)
Phenotypic ratio
of offspring
9 black coat,
normal vision
BbNn
3 black coat,
blind (PRA)
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x
BbNn
3 chocolate coat,
normal vision
1 chocolate coat,
blind (PRA)
Figure 9.6 Using a testcross to determine genotype
X
Testcross:
Genotypes
bb
B_
Two possibilities for the black dog:
BB
Bb
B
Gametes
b
Offspring
or
Bb
All black
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b
B
b
Bb
bb
1 black : 1 chocolate
bb
Figure 9.7 Segregation and fertilization as chance events
Bb male
F1 genotypes
Formation of sperm
Bb female
Formation of eggs
1
2
1
2
B
1
2
B
B
B
b
1
4
F2 genotypes
1
2
b
1
4
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1
4
B
b
b
B
b
b
1
4
Figure 9.8A Examples of inherited traits in humans
Dominant Traits
Recessive Traits
Freckles
No freckles
Widow’s peak
Straight hairline
Free earlobe
Attached earlobe
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Figure 9.8B Pedigree showing inheritance of
deafness in a family from Martha’s Vineyard
Dd
Joshua
Lambert
D?
John
Eddy
Dd
Abigail
Linnell
dd
Jonathan
Lambert
D?
Abigail
Lambert
Dd
Dd
dd
D?
Hepzibah
Daggett
Dd
Elizabeth
Eddy
Dd
Dd
Dd
dd
Female Male
Deaf
Hearing
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Figure 9.9A Offspring produced by parents who
are both carriers for a recessive disorder
Parents
Normal
Dd

Normal
Dd
Sperm
D
DD
Normal
D
Offspring
d
Dd
Normal
(carrier)
Eggs
d
Dd
Normal
(carrier)
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dd
Deaf
Figure 9.9B Achondroplasia, caused by a dominant
allele
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Table 9.9 Some Autosomal Disorders in Humans
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Figure 9.10A Testing a fetus for genetic disorders
Chorionic villus sampling (CVS)
Amniocentesis
Needle inserted
through abdomen to
extract amniotic fluid
Ultrasound
monitor
Fetus
Fetus
Placenta
Uterus
Suction tube inserted
through cervix to extract
tissue from chorionic villi
Ultrasound
monitor
Placenta
Chorionic
villi
Cervix
Cervix
Uterus
Amniotic
fluid
Centrifugation
Fetal
cells
Fetal
cells
Several
weeks
Biochemical
tests
Karyotyping
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Several
hours
Figure 9.10B Ultrasound scanning of a fetus
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9.10 Fetus Ultrasound
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Figure 9.12A Incomplete dominance in snapdragon color
P generation

Red
RR
Gametes
White
rr
r
R
F1 generation
Pink
Rr
Gametes
1
R
2
1
r
2
Sperm
F2 generation
1
R
2
1 r
2
1
2
R
Red
RR
Pink
rR
1
2
r
Pink
Rr
White
rr
Eggs
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Figure 9.12B Incomplete dominance in human
hypercholesterolemia
Genotypes:
Hh
Heterozygous
HH
Homozygous
for ability to make
LDL receptors
hh
Homozygous
for inability to make
LDL receptors
Phenotypes:
LDL
LDL
receptor
Cell
Normal
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Mild disease
Severe disease
Figure 9.13 Multiple alleles for the ABO blood groups
Blood
Group
(Phenotype) Genotypes
Antibodies
Present in
Blood
O
ii
Anti-A
Anti-B
A
IAIA
or
IAi
Anti-B
B
IBIB
or
IBi
Anti-A
AB
IAIB
—
Reaction When Blood from Groups Below Is Mixed with
Antibodies from Groups at Left
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O
A
B
AB
Figure 9.14 Sickle-cell disease, multiple effects of a
single human gene
Individual homozygous
for sickle-cell allele
Sickle-cell (abnormal) hemoglobin
Abnormal hemoglobin crystallizes,
causing red blood cells to become sickle-shaped
Sickle cells
Clumping of cells
and clogging of
small blood vessels
Breakdown of
red blood cells
Physical
weakness
Impaired
mental
function
Anemia
Heart
failure
Paralysis
Pain and
fever
Pneumonia
and other
infections
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Accumulation of
sickled cells in spleen
Brain
damage
Damage to
other organs
Rheumatism
Spleen
damage
Kidney
failure
Figure 9.15 A model for polygenic inheritance of skin color

P generation
aabbcc
AABBCC
(very light) (very dark)

F1 generation
AaBbCc AaBbCc
Sperm
1
8
F2 generation
1
8
1
8
1
8
1
8
1
8
1
8
1
8
1
8
1
8
1
8
Eggs
1
8
1
8
1
8
1
8
1
8
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1
64
6
64
15
64
20
64
20
64
15
64
6
64
1
64
Skin color
15
64
6
64
1
64
Figure 9.16 Environmental factors such as exercise
and sun exposure may produce varying phenotypes
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Figure 9.18 The chromosomal basis of Mendel’s
laws (layer 1)
All round yellow seeds
(RrYy)
F1 generation
R
r
y
Y
R
Y
R
r
Y
y
Metaphase I
of meiosis
(alternative arrangements)
r
y
Anaphase I
of meiosis
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r
R
Y
y
r
R
Y
y
Figure 9.18 The chromosomal basis of Mendel’s
laws (layer 2)
All round yellow seeds
(RrYy)
F1 generation
R
r
y
Y
R
Y
R
r
Y
y
Metaphase I
of meiosis
(alternative arrangements)
r
R
Y
y
r
Anaphase I
of meiosis
y
r
R
r
R
Y
y
r
R
Y
y
Metaphase II
of meiosis
y
Y
Y
y
Y
Gametes
R
R
1
4
RY
y
r
r
1
4
ry
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Y
r
r
1
4
rY
y
y
Y
R
R
1
4
Ry
Figure 9.18 The chromosomal basis of Mendel’s
laws (layer 3)
All round yellow seeds
(RrYy)
F1 generation
R
r
y
Y
R
Y
R
r
Y
y
Metaphase I
of meiosis
(alternative arrangements)
r
R
Y
y
r
Anaphase I
of meiosis
y
r
R
r
R
Y
y
r
R
Y
y
Metaphase II
of meiosis
y
Y
Y
y
Y
Gametes
R
R
1
4
Y
y
r
1
4
RY
F2 generation
r
r
9
ry
r
1
4
rY
Fertilization among the F1 plants
:3
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:3
:1
(See Figure 9.5A)
y
y
Y
R
R
1
4
Ry
Figure 9.19 Experiment involving linked genes in
the sweet pea
Experiment
Purple flower

PpLI
PpLI
Observed
offspring
Phenotypes
Purple long
Purple round
Red long
Red round
Long pollen
Prediction
(9:3:3:1)
215
71
71
24
284
21
21
55
Explanation: linked genes
PL
Parental
diploid cell
PpLI
PI
Meiosis
Most
gametes
PL
PI
Fertilization
Sperm
Most
offspring
PL
PI
PL
PL
PL
PI
PI
PI
PL
PI
PL
Eggs
PI
3 purple long : 1 red round
Not accounted for: purple round and red long
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Figure 9.20A Review: Production of recombinant gametes
A
B
a
b
A
b
a
B
A B
a
Tetrad
b
Crossing over
Gametes
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Figure 9.20B Drosophila melanogaster
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Figure 9.20C Fruit fly experiment demonstrating
the role of crossing over in inheritance
Experiment
Black body,
vestigial
wings
Gray body,
long wings
(wild type)
X
GgLI
ggll
Male
Female
Offspring
Gray long
Black vestigial Gray vestigial Black long
965
944
206
Parental
phenotypes
Recombinant
phenotypes
Recombination frequency =
Explanation
391 recombinants
= 0.17 or 17%
2,300 total offspring
GL
g l
g l
gl
GgLI
(female)
GL
185
g l
Gl
gL
Eggs
GL
gl
gl
gl
Offspring
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Gl
gl
ggll
(male)
gl
Sperm
gL
gl
Figure 9.21A A party in Morgan’s fly room
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Figure 9.21B Mapping genes from crossover data
Chromosome
g
c
l
17%
9%
9.5%
Recombination
frequencies
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Figure 9.21C A partial genetic map of a fruit fly
chromosome
Mutant phenotypes
Short
aristae
Long aristae
(appendages
on head)
Black
body
(g)
Gray
body
(G)
Cinnabar
eyes
(c)
Vestigial
wings
(l)
Brown
eyes
Red
eyes
(C)
Normal
wings
(L)
Red
eyes
Wild-type phenotypes
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Figure 9.22A The X-Y system
(male)
(female)
44
44
+
Parents
diploid
cells
XY
+
XX
22
22
22
+
+
+
X
Y
X
Egg
Sperm
44
+
XX
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Offspring
(diploid)
44
+
XY
Figure 9.22B The X-O system
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22
22
+
+
XX
X
Figure 9.22C The Z-W system
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76
76
+
+
ZW
ZZ
Figure 9.22D Sex determination by chromosome number
32
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16
Figure 9.23A Fruit fly eye color, a sex-linked characteristic
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 9.23B Homozygous, red-eyed female 
white-eyed male
Female
Male

XR XR
Xr Y
Sperm
Eggs XR
Xr
Y
XR Xr
XR Y
R = red-eye allele
r = white-eye allele
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Figure 9.23C Heterozygous female  red-eyed male
Female
Male

XR Xr
XR Y
Sperm
XR
Y
XR
XR XR
XR Y
Xr
Xr XR
Xr Y
Eggs
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Figure 9.23D Heterozygous female  white-eyed male
Female
Male

XR Xr
Xr Y
Sperm
Xr
Y
XR
XR Xr
XR Y
Xr
Xr Xr
Xr Y
Eggs
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Figure 9.24A A test for red-green color blindness
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Figure 9.24B Hemophilia in the royal family of Russia
Queen
victoria
Albert
Alice
Louis
Alexandra
Czar
Nicholas II
of Russia
Alexis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Unnumbered Figure p. 178
Homologous
chromosomes
Fertilization
Alleles, residing
at the same locus
+
Meiosis
Gamete
from other
parent
Paired alleles,
alternate forms
of a gene
Haploid gametes
(allele pairs separate)
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Diploid zygote
(containing
paired alleles)
Unnumbered Figure p. 178
Incomplete
dominance

Red
RR
White
rr
Single
gene
Multiple
genes
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Pink
Rr
Pleiotropy
Multiple traits
Polygenic
inheritance
Single trait
(such as skin color)
Unnumbered Figure p. 178
Genes
alternative
forms called
located
on
(a)
chromosomes
if both same,
if different,
genotype called genotype called
at specific
locations called
(b)
(c)
heterozygous
unexpressed
allele called
expressed
allele called
(d)
(e)
inheritance when phenotype
in between called
(f)
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Unnumbered Figure p. 179
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