5. Figure 15.2
P Generation
F1 Generation
Yellow-round
seeds (YYRR)
Green-wrinkled
seeds (yyrr)
×
Meiosis
Fertilization
Gametes
Y
Y
R R
YR
y
y
r
y r
All F1 plants produce
yellow-round seeds (YyRr).
Meiosis
Metaphase I
Anaphase I
Metaphase II
R R
R R
R R
R R
R R R R
r r
r r
r r
r r
r r r r
Y Y
Y Y
Y Y
Y Y
Y Y Y Y
y y
y y
y y
y y
y
y y y
Gametes
LAW OF SEGREGATION
The two alleles for each
gene separate during
gamete formation.
LAW OF INDEPENDENT
ASSORTMENT Alleles of genes
on nonhomologous chromosomes
assort independently during
gamete formation.
1
2 2
1
1
/4
1
/4
1
/4
1
/4YR yr Yr yR
F2 Generation
3 3Fertilization recombines
the R and r alleles at
random.
Fertilization results in the
9:3:3:1 phenotypic ratio
in the F2 generation.
An F1 × F1 cross-fertilization
9 : 3 : 3 : 1
r
6. Figure 15.2a
P Generation Yellow-round
seeds (YYRR)
Green-wrinkled
seeds (yyrr)
×
Meiosis
Fertilization
Gametes
Y
Y
R R
YR
y
y
r
y r
r
7. Figure 15.2b
F1 Generation
All F1 plants produce
yellow-round seeds (YyRr).
Meiosis
Metaphase I
Anaphase I
Metaphase
II
R R
R R
R R
R R
R R R R
r r
r r
r r
r r
r r r r
Y Y
Y Y
Y Y
Y Y
Y Y Y Y
y y
y y
y y
y y
y
y y y
Gametes
LAW OF SEGREGATION
The two alleles for each
gene separate during
gamete formation.
LAW OF INDEPENDENT
ASSORTMENT Alleles of
genes on nonhomologous
chromosomes assort
independently during gamete
formation.
1
2 2
1
1
/4
1
/4
1
/4
1
/4YR yr Yr yR
8. Figure 15.2c
F2 Generation
3Fertilization
recombines the
R and r alleles
at random.
Fertilization results
in the 9:3:3:1
phenotypic ratio in
the F2 generation.
An F1 × F1 cross-fertilization
9 : 3 : 3 : 1
LAW OF SEGREGATION LAW OF INDEPENDENT
ASSORTMENT
3
16. Figure 15.4
All offspring
had red eyes.
P
Generation
F1
Generation
F2
Generation
F2
Generation
F1
Generation
P
Generation
Eggs
Eggs
Sperm
Sperm
X
X
X
Y
w+
w+
w+
w+
w+
w+
w+
w+ w+
w+
w+
w
w
w
w
w w
RESULTS
EXPERIMENT
CONCLUSION
23. Figure 15.6
Parents
or
Sperm
or
Egg
Zygotes (offspring)
44 +
XY
44 +
XX
22 +
X
22 +
Y
22 +
X
44 +
XX
44 +
XY
22 +
XX
22 +
X
76 +
ZW
76 +
ZZ
32
(Diploid)
16
(Haploid)
(a) The X-Y system
(b) The X-0 system
(c) The Z-W system
(d) The haplo-diploid system
32. Figure 15.8
Early embryo:
X chromosomes
Allele for
orange fur
Allele for
black fur
Two cell
populations
in adult cat:
Cell division and
X chromosome
inactivation
Active X
Inactive X
Active X
Black fur Orange fur
36. Figure 15.9-1
P Generation (homozygous)
Wild type
(gray body, normal wings)
b+
b+
vg+
vg+ b b vg vg
Double mutant
(black body,
vestigial wings)
EXPERIMENT
37. Figure 15.9-2
P Generation (homozygous)
Wild type
(gray body, normal wings)
F1 dihybrid
(wild type)
TESTCROSS
b+
b+
vg+
vg+
b+
b vg+
vg
b b vg vg
b b vg vg
Double mutant
(black body,
vestigial wings)
Double mutant
EXPERIMENT
38. Figure 15.9-3
P Generation (homozygous)
Wild type
(gray body, normal wings)
F1 dihybrid
(wild type)
Testcross
offspring
TESTCROSS
b+
b+
vg+
vg+
b+
b vg+
vg
b b vg vg
b b vg vg
Double mutant
(black body,
vestigial wings)
Double mutant
Eggs
Sperm
EXPERIMENT
Wild type
(gray-normal)
Black-
vestigial
Gray-
vestigial
Black-
normal
b+
vg+ bvg b+
vg b vg+
b+
b vg+
vg bb vg vg b+
bvgvg bb vg+
vg
bvg
39. Figure 15.9-4
P Generation (homozygous)
Wild type
(gray body, normal wings)
F1 dihybrid
(wild type)
Testcross
offspring
TESTCROSS
b+
b+
vg+
vg+
b+
b vg+
vg
b b vg vg
b b vg vg
Double mutant
(black body,
vestigial wings)
Double mutant
Eggs
Sperm
EXPERIMENT
RESULTS
PREDICTED RATIOS
Wild type
(gray-normal)
Black-
vestigial
Gray-
vestigial
Black-
normal
b+
vg+ bvg b+
vg b vg+
b+
b vg+
vg bb vg vg b+
bvgvg bb vg+
vg
965 944 206 185
1
1
1
1
1
0
1
0
If genes are located on different chromosomes:
If genes are located on the same chromosome and
parental alleles are always inherited together:
:
:
:
:
:
:
:
:
:
bvg
45. Figure 15.UN02
Gametes from green-
wrinkled homozygous
recessive parent (yyrr)
Gametes from yellow-round
dihybrid parent (YyRr)
Recombinant
offspring
Parental-
type
offspring
YR yr Yr yR
yr
YyRr yyrr Yyrr yyRr
47. Figure 15.10 Testcross
parents
Replication
of chromosomes
Gray body, normal wings
(F1 dihybrid)
Black body, vestigial wings
(double mutant)
Replication
of chromosomes
Meiosis I
Meiosis II
Meiosis I and II
Recombinant
chromosomes
Eggs
b+
vg+
b vg
b+
vg+
b+
vg+
b+
vg+
b+
vg
b vg+
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b+
vg+ b+
vgb vg b vg+
Testcross
offspring
965
Wild type
(gray-normal)
944
Black-
vestigial
206
Gray-
vestigial
185
Black-
normal
Sperm
Parental-type offspring Recombinant offspring
Recombination
frequency
391 recombinants
2,300 total offspring
× 100 = 17%=
b+
vg+
b vg+b+
vgb vg
b vg b vg b vg b vg
b vg
48. Figure 15.10a
Testcross
parents
Replication
of chromosomes
Gray body, normal wings
(F1 dihybrid)
Black body, vestigial wings
(double mutant)
Replication
of chromosomes
Meiosis I
Meiosis II
Meiosis I and II
Recombinant
chromosomes
Eggs
b+
vg+
b vg
b+
vg+
b+
vg+
b+
vg+
b+
vg
b vg+
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b vg
b+
vg+
b+
vgb vg
b vg+
Sperm
b vg
66. Figure 15.14
(a) Deletion
(b) Duplication
(c) Inversion
(d) Translocation
A deletion removes a chromosomal segment.
A duplication repeats a segment.
An inversion reverses a segment within a
chromosome.
A translocation moves a segment from one
chromosome to a nonhomologous chromosome.
A B C D E F G H
A B C E F G H
A B C D E F G H
A B C D E F G HB C
A B C D E F G H
A D C B E F G H
A B C D E F G H M N O P Q R
GM N O C HFED A B P Q R
67. Figure 15.14a
(a) Deletion
(b) Duplication
A deletion removes a chromosomal segment.
A duplication repeats a segment.
BA C D E F G H
A B C D E F G H
A B C D E F G HB C
A B C E F G H
68. Figure 15.14b
(c) Inversion
(d) Translocation
An inversion reverses a segment within a
chromosome.
A translocation moves a segment from one
chromosome to a nonhomologous chromosome.
A B C D E F G H
A D C B E F G H
A B C D E F G H M N O P Q R
GM N O C HFED A B P Q R
79. Figure 15.17
(a) Homozygote
Paternal
chromosome
Maternal
chromosome
Normal Igf2 allele
is expressed.
Normal Igf2 allele
is not expressed.
Normal-sized mouse
(wild type)
Mutant Igf2 allele
inherited from mother
Mutant Igf2 allele
inherited from father
Normal-sized mouse (wild type) Dwarf mouse (mutant)
Normal Igf2 allele
is expressed.
Mutant Igf2 allele
is expressed.
Mutant Igf2 allele
is not expressed.
Normal Igf2 allele
is not expressed.
(b) Heterozygotes
81. Figure 15.17b
Mutant Igf2 allele
inherited from mother
Mutant Igf2 allele
inherited from father
Normal-sized mouse (wild type) Dwarf mouse (mutant)
Normal Igf2 allele
is expressed.
Mutant Igf2 allele
is expressed.
Mutant Igf2 allele
is not expressed.
Normal Igf2 allele
is not expressed.
(b) Heterozygotes
86. Figure 15.UN03
P generation
gametes
Sperm Egg
This F1 cell has 2n = 6 chromo-
somes and is heterozygous for all
six genes shown (AaBbCcDdEeFf).
Red = maternal; blue = paternal.
Each chromosome has
hundreds or thousands
of genes. Four (A, B, C,
F) are shown on this one.
The alleles of unlinked
genes are either on
separate chromosomes
(such as d and e)
or so far apart on the
same chromosome
(c and f) that they
assort independently.
Genes on the same chromo-
some whose alleles are so
close together that they do
not assort independently
(such as a, b, and c) are said
to be genetically linked.
D
C
B
A
F
E d
c
b
a
f
e
D
C
B
A
F
e
d
E
f
c ba