Fig. 9-1, p. 156
Genes occur in pairs on
homologous chromosomes.
The members of each pair of
genes may be identical in DNA
sequence, or they may be
slightly different (alleles).
Fig. 9-2, p. 157
1
2
3
Fig. 9-3, p. 157
DNA replication
DNA replication
meiosis I
meiosis I
meiosis II
meiosis II
(gametes)
(gametes)
(zygote)
Fig. 9-4, p. 158
DNA replication
DNA replication
meiosis I
meiosis I
meiosis II
meiosis II
(gametes)
(gametes)
(zygote)
Stepped Art
Fig. 9-4, p. 158
Fig. 9-5, p. 159
male gametes
female gametes
A Making a Punnett square. The possible parental
gametes are listed on the top and left sides of the
grid (in circles). Each square is filled in with the
combination of alleles that would result if the
gametes in the corresponding row and column met up.
Fig. 9-5a, p. 159
offspring
Heterozygous
parent
Heterozygous
parent
B A Punnett square shows that the ratio of dominantto-recessive phenotypes among offspring of a
monohybrid cross is about 3:1 (3 purple to 1 white).
Fig. 9-5b, p. 159
female gametes
male gametes
offspring
Heterozygous
parent
A) Making a Punnett square. The possible
parental gametes are listed on the top and left
sides of the grid (in circles). Each square is filled
in with the combination of alleles that would
result if the gametes in the corresponding row
and column met up.
Heterozygous
parent
B) A Punnett square shows that the ratio of dominant-to-recessive
phenotypes among offspring of a monohybrid cross is about 3:1 (3
purple to 1 white).
Stepped Art
Fig. 9-5b, p. 159
A) This example shows just two pairs of
homologous chromosomes in the nucleus of
a diploid (2n) reproductive cell. Maternal and
paternal chromosomes, shown in pink and
blue, have already been duplicated.
B) Either chromosome of a pair may get attached
to either spindle pole during meiosis I. With two
pairs of homologous chromosomes, there are
two different ways that the maternal and paternal
homologues can get attached to opposite
spindle poles.
or
meiosis I
meiosis I
meiosis II
meiosis II
C) Two nuclei form with each scenario, so
there are a total of four possible combinations
of parental chromosomes in the nuclei that
form after meiosis I.
D) Thus, when sister chromatids separate
during meiosis II, the gametes that result
have one of four possible combinations of
maternal and paternal chromosomes.
gamete genotype:
Stepped Art
Fig. 9-6, p. 160
Fig. 9-7, p. 161
parent plant
homozygous
for purple flowers
and long stems
parent plant
homozygous
for white flowers
and short stems
dihybrid
four types of gametes
Fig. 9-7a, p. 161
Fig. 9-7b, p. 161
parent plant
parent plant
homozygous
homozygous
for purple flowers for white flowers
and long stems and short stems
2) dihybrid
3) four types of gametes
Stepped Art
Fig. 9-7b, p. 161
Fig. 9-8, p. 162
Genotypes:
Phenotypes
(blood type):
A
AB
B
O
Fig. 9-9, p. 163
homozygous
parent (RR)
x
homozygous
parent (rr)
heterozygous
offspring (Rr)
A Cross a red-flowered with a white-flowered plant,
and all of the offspring will be pink heterozygotes.
Fig. 9-10a, p. 163
B If two of the heterozygotes
are crossed, the phenotypes
of the resulting offspring will
occur in a 1:2:1 ratio.
Fig. 9-10b, p. 163
Fig. 9-11, p. 164
Fig. 9-12, p. 165
Fig. 9-12a, p. 165
Fig. 9-12b, p. 165
Height (centimeters)
60
60
60
0
0
0
A Plant grown
at high elevation
(3,060 meters
above sea level)
B Plant grown
at mid-elevation
(1,400 meters
above sea level)
C Plant grown
at low elevation
(30 meters
above sea level)
Fig. 9-14, p. 166
male
female
marriage/mating
offspring
individual showing
trait being studied
sex not
specified
generation
A) Standard symbols used in
pedigrees
*Gene not expressed in this carrier.
B) A pedigree for polydactyly, which is characterized by extra
fingers, toes, or both. The black numbers signify the number of
fingers on each hand; the blue numbers signify the number of
toes on each foot.
Stepped Art
Fig. 9-15, p. 167
Table 9-1, p. 168
normal
mother
affected
father
meiosis
and gamete
formation
affected child
normal child
disorder-causing
allele (dominant)
Fig. 9-16a, p. 168
Fig. 9-16b, p. 168
Fig. 9-17, p. 169
carrier mother
carrier father
meiosis
and gamete
formation
affected child
carrier child
normal child
disorder-causing
allele (recessive)
Fig. 9-17a, p. 169
Table 9-2, p. 169
Table 9-3, p. 170
Fig. 9-18 (top), p. 170
Fig. 9-18 (a-d), p. 170
Fig. 9-19, p. 171
Table 9-4, p. 171
Metaphase I
Anaphase I
Telophase I
Metaphase II Anaphase II Telophase II
Fig. 9-20a, p. 172
Fig. 9-20b, p. 172
Metaphase I
Anaphase I
Telophase I
Metaphase II Anaphase II Telophase II
Stepped Art
Fig. 9-20b, p. 172
Fig. 9-20c, p. 172
p. 174
Fig. 9-23, p. 175
Fig. 9-24, p. 177