6. Figure 9.2C_s3
White
1 Removal of
stamens
Stamens
Carpel
Parents
(P)
2 Transfer
Purple of pollen
3 Carpel matures
into pea pod
4 Seeds from
pod planted
Offspring
(F1)
8. Figure 9.3A_s3
The Experiment
P generation
(true-breeding
parents)
×
Purple
flowers
F1 generation
White
flowers
All plants have
purple flowers
Fertilization
among F1 plants
(F1 × F1)
F2 generation
3
4
1 of plants
of plants
4
have purple flowers have white flowers
14. Practice Problems
For each phenotypes write the possible genotypes:
1.
Constricted pods
2.
Tall plant
3.
Round seeds
4.
White flowers
5.
Yellow seeds
17. Figure 9.3B_s3
The Explanation
P generation
Genetic makeup (alleles)
White flowers
Purple flowers
PP
pp
Gametes
All P
All p
F1 generation
(hybrids)
All Pp
Gametes
1
2
P
Alleles
segregate
1
2
p
Fertilization
Sperm from F1 plant
F2 generation
P
Phenotypic ratio
3 purple : 1 white
Genotypic ratio
1 PP : 2 Pp : 1 pp
P
Eggs
from F1
plant
p
p
PP
Pp
Pp
pp
18. 25% or ¼ of the offspring have
the homozygous dominant
genotype (FF)
50% or 2/4 have the
heterozygous genotype (Ff)
25% or ¼ have the homozygous
recessive genotype (ff)
– A genotypic ratio of 1:2:1
This results in 75% or ¾ offspring – FF : Ff : ff
having purple flowers
25% or ¼ offspring having white
flowers
– A phenotypic ratio of 3:1
– Dominant : Recessive
19. Practice Problems
Cross a pea plant that is heterozygous for yellow
seed color with another pea plant that is also
heterozygous for yellow seed color.
What are the genotypic and phenotypic ratios?
24. Figure 9.16_s3
F1 generation
R
r
All yellow round seeds
(RrYy)
y
Y
Y
R
r
r
R
y
Metaphase I
of meiosis
R
Y
y
r
r
R
Y
y
Anaphase I
Y
y
R
r
Y
Metaphase II
R
Y
y
r
y
Gametes
Y
Y
R
R
1
4
RY
y
Y
r
r
1
4
Y
r
y
r
ry
F2 generation 9
Fertilization
:3
:3
:1
1
4
rY
y
y
R
R
1
4
Ry
26. Dihybrid crosses
Dihybrid crosses consider two pairs of
contrasting traits.
• In this example two plants, each
heterozygous for Yellow and
Round Seeds are crossed (YyRr).
•The result is:
•9/16 plants with yellow and
round seeds.
•3/16 plants with yellow and
wrinkled seeds.
•3/16 plants with green and
round seeds.
•1/16 plants with green and
wrinkled seeds.
•Phenotypic ratio of 9:3:3:1
27. Practice Problem
If you cross a pea plant that is heterozygous for axial
flowers and has green seeds, with a pea plant that
has terminal flowers and is heterozygous for yellow
seeds, what is the probability the offspring will have
– axial flowers and yellow seeds?
– Axial flowers and green seeds?
– Terminal flowers and yellow seeds?
– Terminal flowers and green seeds?
What is the phenotypic ratio?
30. Figure 9.5B
Blind
Blind
Phenotypes
Genotypes
Black coat,
normal vision
B_N_
Black coat,
blind (PRA)
B_nn
Chocolate coat,
normal vision
bbN_
Chocolate coat,
blind (PRA)
bbnn
Mating of double heterozygotes (black coat, normal vision)
BbNn
BbNn
×
Blind
Blind
Phenotypic ratio
of the offspring
9
Black coat,
normal vision
3
Black coat,
blind (PRA)
3
Chocolate coat,
normal vision
1
Chocolate coat,
blind (PRA)
Student Misconceptions and Concerns
The authors note that Mendel’s work was published in 1866, seven years after Darwin published Origin of Species. Consider challenging your students to consider whether Mendel’s findings supported Darwin’s ideas. Some scientists have noted that Darwin often discussed the evolution of traits by matters of degree. Yet, Mendel’s selection of pea plant traits typically showed complete dominance, rather than the possibility for such gradual inheritance.
Teaching Tips
1. In Module 9.2, the authors make the analogy between genes and playing cards, noting that each are shuffled but retain their original identity. This analogy may form a very useful reference point for your students and can be used later, as new principles of genetics are discussed.
2. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
Student Misconceptions and Concerns
The authors note that Mendel’s work was published in 1866, seven years after Darwin published Origin of Species. Consider challenging your students to consider whether Mendel’s findings supported Darwin’s ideas. Some scientists have noted that Darwin often discussed the evolution of traits by matters of degree. Yet, Mendel’s selection of pea plant traits typically showed complete dominance, rather than the possibility for such gradual inheritance.
Teaching Tips
1. In Module 9.2, the authors make the analogy between genes and playing cards, noting that each are shuffled but retain their original identity. This analogy may form a very useful reference point for your students and can be used later, as new principles of genetics are discussed.
2. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
Student Misconceptions and Concerns
The authors note that Mendel’s work was published in 1866, seven years after Darwin published Origin of Species. Consider challenging your students to consider whether Mendel’s findings supported Darwin’s ideas. Some scientists have noted that Darwin often discussed the evolution of traits by matters of degree. Yet, Mendel’s selection of pea plant traits typically showed complete dominance, rather than the possibility for such gradual inheritance.
Teaching Tips
1. In Module 9.2, the authors make the analogy between genes and playing cards, noting that each are shuffled but retain their original identity. This analogy may form a very useful reference point for your students and can be used later, as new principles of genetics are discussed.
2. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
Figure 9.2C_s3 Mendel’s technique for cross-fertilization of pea plants (step 3)
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
2. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP pp and (b) Pp pp.
3. For students struggling with basic terminology, an analogy between a genetic trait and a pair of shoes might be helpful. A person might wear a pair of shoes in which both shoes match (homozygous), or less likely, a person might wear shoes that do not match (heterozygous).
4. Another analogy that might help struggling students is a pair of people trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. This (heterozygous) couple eats at home (the dominant allele “wins”).
Figure 9.3A_s3 Crosses tracking one character (flower color) (step 3)
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
2. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP pp and (b) Pp pp.
3. For students struggling with basic terminology, an analogy between a genetic trait and a pair of shoes might be helpful. A person might wear a pair of shoes in which both shoes match (homozygous), or less likely, a person might wear shoes that do not match (heterozygous).
4. Another analogy that might help struggling students is a pair of people trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. This (heterozygous) couple eats at home (the dominant allele “wins”).
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
2. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP pp and (b) Pp pp.
3. For students struggling with basic terminology, an analogy between a genetic trait and a pair of shoes might be helpful. A person might wear a pair of shoes in which both shoes match (homozygous), or less likely, a person might wear shoes that do not match (heterozygous).
4. Another analogy that might help struggling students is a pair of people trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. This (heterozygous) couple eats at home (the dominant allele “wins”).
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
1. This early material introduces many definitions that are vital to understanding the later discussions in this chapter. Therefore, students need to be encouraged to master these definitions immediately. This may be a good time for a short quiz to encourage their progress.
2. Many students benefit from a little quick practice with a Punnett square. Have them try these crosses for practice: (a) PP pp and (b) Pp pp.
3. For students struggling with basic terminology, an analogy between a genetic trait and a pair of shoes might be helpful. A person might wear a pair of shoes in which both shoes match (homozygous), or less likely, a person might wear shoes that do not match (heterozygous).
4. Another analogy that might help struggling students is a pair of people trying to make a decision about where to eat tonight. One person wants to eat at a restaurant, the other wants to eat a meal at home. This (heterozygous) couple eats at home (the dominant allele “wins”).
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
Many students have trouble with the basic statistics that are necessary for many of these calculations. Give your students some practice. Consider having them work in pairs, each with a pair of dice (for large class sizes, this can be done in laboratories). Let them calculate the odds of rolling three sixes in a row and other possibilities.
Figure 9.3B_s3 An explanation of the crosses in Figure 9.3A (step 3)
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
Figure 9.4 can be of great benefit when introducing genetic terminology. For students struggling to think abstractly, such a visual aid may be essential when describing these features in lecture.
Figure 9.4 Three gene loci on homologous chromosomes
Student Misconceptions and Concerns
This section of the chapter relies upon a good understanding of the chromosome-sorting process of meiosis. If students were not assigned Chapter 8, and meiosis has not otherwise been addressed, it will be difficult for students to understand the chromosomal basis of inheritance or linked genes.
Teaching Tips
Figure 9.16 requires an understanding of meiosis and the general cell cycle from Chapter 8. Students may need to be reminded that chromosomes are duplicated in the preceding interphase, as indicated in the first step. Furthermore, students may not initially notice that this diagram represents four possible outcomes, not stages of any one meiotic cycle.
Figure 9.16_s3 The chromosomal basis of Mendel’s laws (step 3)
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
Understanding dihybrid crosses may be the most difficult concept in this chapter. Consider spending additional time to make these ideas very clear. As the text indicates, dihybrid crosses are essentially two monohybrid crosses occurring simultaneously.
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
Understanding dihybrid crosses may be the most difficult concept in this chapter. Consider spending additional time to make these ideas very clear. As the text indicates, dihybrid crosses are essentially two monohybrid crosses occurring simultaneously.
Student Misconceptions and Concerns
Students using Punnett squares need to be reminded that the calculations are expected statistical probabilities and not absolutes. We would expect that any six playing cards dealt might be half black and half red, but we frequently find that this is not true. This might be a good time to show how larger sample sizes increase the likelihood that sampling will reflect expected ratios.
Teaching Tips
Understanding dihybrid crosses may be the most difficult concept in this chapter. Consider spending additional time to make these ideas very clear. As the text indicates, dihybrid crosses are essentially two monohybrid crosses occurring simultaneously.
Figure 9.5B Independent assortment of two genes in the Labrador retriever
