5. Fig. 15-2
P Generation Yellow-round
seeds (YYRR)
Y
F1 Generation
Y
R R
R Y
r
r
r
y
y
y
Meiosis
Fertilization
Gametes
Green-wrinkled
seeds (yyrr)
All F1 plants produce
yellow-round seeds (YyRr)
R R
YY
r r
y y
Meiosis
R R
Y Y
r r
y y
Metaphase I
Y Y
R Rrr
y y
Anaphase I
r r
y Y
Metaphase IIR
Y
R
y
yyy
RR
YY
rrrr
yYY
R R
yRYryrYR1/4
1/4
1/4
1/4
F2 Generation
Gametes
An F1 F1 cross-fertilization
9 : 3 : 3 : 1
LAW OF INDEPENDENT
ASSORTMENT Alleles of genes
on nonhomologous
chromosomes assort
independently during gamete
formation.
LAW OF SEGREGATION
The two alleles for each gene
separate during gamete
formation.
1
2
33
2
1
7. Fig. 15-2b
0.5 mm
Meiosis
Metaphase I
Anaphase I
Metaphase II
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
4
yr 1 4
Yr1
4 YR
3 3
F1 Generation
1 4
yR
R
R
R
R
RR
R
R R R R
R
Y
Y
Y Y
Y
YY
Y
YY
YY
y
r r
rr
r r
rr
r r r r
y
y
y
y
y
y y
yyy
y
All F1 plants produce
yellow-round seeds (YyRr)
1
2 2
1
22. Fig. 15-6
44 +
XY
Parents
44 +
XX
22 +
X
22 +
X
22 +
Yor +
44 +
XX or
Sperm Egg
44 +
XY
Zygotes (offspring)
(a) The X-Y system
22 +
XX
22 +
X
(b) The X-0 system
76 +
ZW
76 +
ZZ
(c) The Z-W system
32
(Diploid)
16
(Haploid)
(d) The haplo-diploid system
23. Fig. 15-6a
(a) The X-Y system
44 +
XY
44 +
XX
Parents
44 +
XY
44 +
XX
22 +
X
22 +
X
22 +
Yor
or
Sperm Egg
+
Zygotes (offspring)
32. Fig. 15-8
X chromosomes
Early embryo:
Allele for
orange fur
Allele for
black fur
Cell division and
X chromosome
inactivationTwo cell
populations
in adult cat:
Active X
Active X
Inactive X
Black fur Orange fur
36. Fig. 15-9-1
EXPERIMENT
P Generation (homozygous)
Wild type
(gray body,
normal wings)
Double mutant
(black body,
vestigial wings)
b b vg vgb+ b+ vg+ vg+
37. Fig. 15-9-2
EXPERIMENT
P Generation (homozygous)
Wild type
(gray body,
normal wings)
Double mutant
(black body,
vestigial wings)
b b vg vg
b b vg vg
Double mutant
TESTCROSS
b+ b+ vg+ vg+
F1 dihybrid
(wild type)
b+ b vg+ vg
38. Fig. 15-9-3
EXPERIMENT
P Generation (homozygous)
Wild type
(gray body,
normal wings)
Double mutant
(black body,
vestigial wings)
b b vg vg
b b vg vg
Double mutant
TESTCROSS
b+ b+ vg+ vg+
F1 dihybrid
(wild type)
b+ b vg+ vg
Testcross
offspring Eggs b+ vg+ b vg b+ vg b vg+
Black-
normal
Gray-
vestigial
Black-
vestigial
Wild type
(gray-normal)
b vg
Sperm
b+ b vg+ vg b b vg vg b+ b vg vgb b vg+ vg
39. Fig. 15-9-4
EXPERIMENT
P Generation (homozygous)
RESULTS
Wild type
(gray body,
normal wings)
Double mutant
(black body,
vestigial wings)
b b vg vg
b b vg vg
Double mutant
TESTCROSS
b+ b+ vg+ vg+
F1 dihybrid
(wild type)
b+ b vg+ vg
Testcross
offspring Eggs b+ vg+ b vg b+ vg b vg+
Black-
normal
Gray-
vestigial
Black-
vestigial
Wild type
(gray-normal)
b vg
Sperm
b+ b vg+ vg b b vg vg b+ b vg vgb b vg+ vg
PREDICTED RATIOS
If genes are located on different chromosomes:
If genes are located on the same chromosome and
parental alleles are always inherited together:
1
1
1
1
1 1
0 0
965 944 206 185
:
:
:
:
:
:
:
:
:
44. Fig. 15-UN2
YyRr
Gametes from green-
wrinkled homozygous
recessive parent (yyrr)
Gametes from yellow-round
heterozygous parent (YyRr)
Parental-
type
offspring
Recombinant
offspring
yr
yyrr Yyrr yyRr
YR yr Yr yR
46. Fig. 15-10
Testcross
parents
Replication
of chromo-
somes
Gray body, normal wings
(F1 dihybrid)
Black body, vestigial wings
(double mutant)
Replication
of chromo-
somes
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
Recombinant
chromosomes
Meiosis I and II
Meiosis I
Meiosis II
b vg+b+ vgb vgb+ vg+
Eggs
Testcross
offspring
965
Wild type
(gray-normal)
944
Black-
vestigial
206
Gray-
vestigial
185
Black-
normal
b+ vg+
b vg b vg
b vg b+ vg
b vg b vg
b vg+
Sperm
b vg
Parental-type offspring Recombinant offspring
Recombination
frequency =
391 recombinants
2,300 total offspring
100 = 17%
47. Fig. 15-10a
Testcross
parents
Replication
of chromo-
somes
Gray body, normal wings
(F1 dihybrid)
Black body, vestigial wings
(double mutant)
Replication
of chromo-
somes
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
Recombinant
chromosomes
Meiosis I and II
Meiosis I
Meiosis II
Eggs Sperm
b+ vg+
b vg b+ vg b vgb vg+
57. Fig. 15-13-1
Meiosis I
(a) Nondisjunction of homologous
chromosomes in meiosis I
(b) Nondisjunction of sister
chromatids in meiosis II
Nondisjunction
58. Fig. 15-13-2
Meiosis I
Nondisjunction
(a) Nondisjunction of homologous
chromosomes in meiosis I
(b) Nondisjunction of sister
chromatids in meiosis II
Meiosis II
Nondisjunction
59. Fig. 15-13-3
Meiosis I
Nondisjunction
(a) Nondisjunction of homologous
chromosomes in meiosis I
(b) Nondisjunction of sister
chromatids in meiosis II
Meiosis II
Nondisjunction
Gametes
Number of chromosomes
n + 1 n + 1 n + 1n – 1 n – 1 n – 1 n n
65. Fig. 15-15
Deletion
A B C D E F G H A B C E F G H
(a)
(b)
(c)
(d)
Duplication
Inversion
Reciprocal
translocation
A B C D E F G H
A B C D E F G H
A B C D E F G H
A B C B C D E F G H
A D C B E F G H
M N O C D E F G H
M N O P Q R A B P Q R
76. Fig. 15-18
Normal Igf2 allele
is expressed
Paternal
chromosome
Maternal
chromosome
Normal Igf2 allele
is not expressed
Mutant Igf2 allele
inherited from mother
(a) Homozygote
Wild-type mouse
(normal size)
Mutant Igf2 allele
inherited from father
Normal size 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
77. Fig. 15-18a
Normal Igf2 allele
is expressed
Paternal
chromosome
Maternal
chromosome
(a) Homozygote
Wild-type mouse
(normal size)
Normal Igf2 allele
is not expressed
78. Fig. 15-18b
Mutant Igf2 allele
inherited from mother
Mutant Igf2 allele
inherited from father
Normal size 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
84. Fig. 15-UN4
EggSperm
P generation
gametes
C
B
AD E
F
D
F E
A
B
C
e
d
f
c ba
d
f
e
c
b
a
This F1 cell has 2n = 6
chromosomes 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 linked.