Fig. 9-1, p. 156

Fig. 9-2, p. 157

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. 9-3, p. 157

1

2

3

Fig. 9-4, p. 158

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. 9-5, p. 159

Fig. 9-5a, p. 159

female gametes

mal

e g

amet

es

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. 9-5b, p. 159

offspring

Heterozygous parent

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).

Fig. 9-5b, p. 159

offspring

Heterozygous parent

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

female gametes

mal

e g

amet

es

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. 9-6, p. 160

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.

meiosis I 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.

meiosis II meiosis II

gamete genotype:

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

Stepped Art

Fig. 9-7, p. 161

Fig. 9-7a, 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. 9-7b, p. 161

Fig. 9-7b, p. 161

Stepped Art

parent plant homozygous

for purple flowers and long stems

parent plant homozygous

for white flowers and short stems

2) dihybrid

3) four types of gametes

Fig. 9-8, p. 162

Fig. 9-9, p. 163

Genotypes:

Phenotypes (blood type): A AB B O

Fig. 9-10a, 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. 9-10b, 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. 9-11, p. 164

Fig. 9-12, p. 165

Fig. 9-12a, p. 165

Fig. 9-12b, p. 165

Fig. 9-14, p. 166

60 60 60

Hei

gh

t (c

enti

met

ers)

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)

marriage/mating

female

male

offspring

individual showing trait being studiedsex not specifiedgeneration

A) Standard symbols used in pedigrees

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.

Fig. 9-15, p. 167

*Gene not expressed in this carrier.

Stepped Art

Table 9-1, p. 168

Fig. 9-16a, p. 168

normal mother

affected father

meiosis and gamete formation

affected child

normal child

disorder-causing allele (dominant)

Fig. 9-16b, p. 168

Fig. 9-17, p. 169

Fig. 9-17a, p. 169

carrier mother carrier father

meiosis and gamete formation

affected child

carrier child

normal childdisorder-causing allele (recessive)

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

Fig. 9-20a, p. 172

Metaphase I Anaphase I Telophase I Metaphase II Anaphase II Telophase II

Fig. 9-20b, p. 172

Fig. 9-20b, p. 172

Stepped Art

Metaphase I Anaphase I Telophase I Metaphase II Anaphase II Telophase II

Fig. 9-20c, p. 172

p. 174

Fig. 9-23, p. 175

Fig. 9-24, p. 177