4. Figure 15.2
P Generation Yellow-round Green-wrinkled
seeds (YYRR) seeds (yyrr)
Y ry
×
R R r
Y y
Meiosis
Fertilization
R Y y r
Gametes
All F1 plants produce
yellow-round seeds (YyRr).
F1 Generation
R R
y y
r r
Y Y
Meiosis
LAW OF SEGREGATION LAW OF INDEPENDENT
The two alleles for each r ASSORTMENT Alleles of genes
R r R
gene separate during on nonhomologous chromosomes
gamete formation. Metaphase I assort independently during
gamete formation.
Y y Y y
1 1
R r r R
Anaphase I
Y y Y y
R r r R
2 2
Y y Metaphase II Y y
Y y Y
Y y Y y y
Gametes
R R r r r r R R
1
/4 YR 1
/4 yr 1
/4 Yr 1
/4 yR
F2 Generation An F1 × F1 cross-fertilization
3 Fertilization recombines 3 Fertilization results in the
the R and r alleles at 9:3:3:1 phenotypic ratio
random. 9 :3 :3 :1 in the F2 generation.
10. Figure 15.4
EXPERIMENT
P
Generation
F1 All offspring
Generation had red eyes.
RESULTS
F2
Generation
CONCLUSION
P X
w+
X
w
Generation X Y
w+
w
Sperm
Eggs
F1 w+
w+ w+
Generation
w
w+
Sperm
Eggs
w+ w+
F2 w+
w+
Generation
w w
w
w+
15. Figure 15.6
44 + 44 +
XY Parents XX
22 + 22 + 22 +
X or Y X
Sperm Egg
44 + 44 +
XX or XY
(a) The X-Y system Zygotes (offspring)
22 + 22 +
XX X
(b) The X-0 system
76 + 76 +
ZW ZZ
(c) The Z-W system
32 16
(Diploid) (Haploid)
(d) The haplo-diploid system
22. Figure 15.8
X chromosomes
Allele for
orange fur
Early embryo:
Allele for
black fur
Cell division and
X chromosome
Two cell inactivation
populations
in adult cat: Active X
Inactive X
Active X
Black fur Orange fur
25. Figure 15.9-4
EXPERIMENT P Generation (homozygous)
Double mutant
Wild type (black body,
(gray body, normal wings) vestigial wings)
b+ b+ vg+ vg+ b b vg vg
F1 dihybrid Double mutant
TESTCROSS
(wild type)
b+ b vg+ vg b b vg vg
Testcross
offspring Eggs b+ vg+ b vg b+ vg b vg+
Wild type Black- Gray- Black-
(gray-normal) vestigial vestigial normal
b vg
Sperm
b+ b vg+ vg b b vg vg b+ b vg vg b b vg+ vg
PREDICTED RATIOS
If genes are located on different chromosomes: 1 : 1 : 1 : 1
If genes are located on the same chromosome and
parental alleles are always inherited together: 1 : 1 : 0 : 0
RESULTS 965 : 944 : 206 : 185
31. Figure 15.UN02
Gametes from yellow-round
dihybrid parent (YyRr)
YR yr Yr yR
Gametes from green-
wrinkled homozygous yr
recessive parent (yyrr)
YyRr yyrr Yyrr yyRr
Parental- Recombinant
type offspring
offspring
33. Figure 15.10 Testcross Gray body, normal wings Black body, vestigial wings
parents (F1 dihybrid) (double mutant)
b+ vg+ b vg
b vg b vg
Replication Replication
of chromosomes of chromosomes
b+ vg+ b vg
b+ vg+ b vg
b vg b vg
b vg b vg
Meiosis I
b+ vg+
Meiosis I and II
b+ vg
b vg+
b vg
Meiosis II
Recombinant
chromosomes
b+ vg+ b vg b+ vg b vg+
Eggs
Testcross 965 944 206 185
offspring Wild type Black- Gray- Black-
(gray-normal) vestigial vestigial normal b vg
b+ vg+ b vg b+ vg b vg+
b vg b vg b vg b vg Sperm
Parental-type offspring Recombinant offspring
Recombination 391 recombinants
= × 100 = 17%
frequency 2,300 total offspring
41. Figure 15.13-3
Meiosis I
Nondisjunction
Meiosis II
Non-
disjunction
Gametes
n+1 n+1 n−1 n−1 n+1 n−1 n n
Number of chromosomes
(a) Nondisjunction of homo- (b) Nondisjunction of sister
logous chromosomes in chromatids in meiosis II
meiosis I
46. Figure 15.14
(a) Deletion
A B C D E F G H
A deletion removes a chromosomal segment.
A B C E F G H
(b) Duplication
A B C D E F G H
A duplication repeats a segment.
A B C B C D E F G H
(c) Inversion
A B C D E F G H
An inversion reverses a segment within a
chromosome.
A D C B E F G H
(d) Translocation
A B C D E F G H M N O P Q R
A translocation moves a segment from one
chromosome to a nonhomologous chromosome.
M N O C D E F G H A B P Q R
55. Figure 15.17
Normal Igf2 allele
is expressed.
Paternal
chromosome
Maternal
chromosome Normal-sized mouse
Normal Igf2 allele (wild type)
is not expressed.
(a) Homozygote
Mutant Igf2 allele Mutant Igf2 allele
inherited from mother inherited from father
Normal-sized mouse (wild type) Dwarf mouse (mutant)
Normal Igf2 allele Mutant Igf2 allele
is expressed. is expressed.
Mutant Igf2 allele Normal Igf2 allele
is not expressed. is not expressed.
(b) Heterozygotes
Figure 15.2 The chromosomal basis of Mendel ’s laws.
Figure 15.3 Morgan ’s first mutant.
Figure 15.4 Inquiry: In a cross between a wild-type female fruit fly and a mutant white-eyed male, what color eyes will the F 1 and F 2 offspring have?
Figure 15.5 Human sex chromosomes.
Figure 15.6 Some chromosomal systems of sex determination.
Figure 15.7 The transmission of X-linked recessive traits.
Figure 15.8 X inactivation and the tortoiseshell cat.
Figure 15.9 Inquiry: How does linkage between two genes affect inheritance of characters?
Figure 15.UN01 In-text figure, p. 294
Figure 15.UN02 In-text figure, p. 294
Figure 15.10 Chromosomal basis for recombination of linked genes.
Figure 15.11 Research Method: Constructing a Linkage Map
Figure 15.13 Meiotic nondisjunction.
Figure 15.14 Alterations of chromosome structure.
Figure 15.15 Down syndrome.
Figure 15.16 Translocation associated with chronic myelogenous leukemia (CML).
Figure 15.17 Genomic imprinting of the mouse Igf2 gene.
Figure 15.18 Variegated leaves from English holly (Ilex aquifolium).