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2. Standardized Test Prep
Resources
Chapter Presentation
Visual Concepts
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Standardized Test Prep

3. Chapter 9 Table of Contents Section 1 Mendel’s Legacy
Fundamentals of Genetics
Table of Contents
Section 1 Mendel’s Legacy
Section 2 Genetic Crosses

4. Chapter 9 Objectives Section 1 Mendel’s Legacy
Describe how Mendel was able to control how his pea plants were pollinated.
Describe the steps in Mendel’s experiments on true-breeding garden peas.
Distinguish between dominant and recessive traits.
State two laws of heredity that were developed from Mendel’s work.
Describe how Mendel’s results can be explained by scientific knowledge of genes and chromosomes.

5. Section 1 Mendel’s Legacy
Chapter 9
Gregor Mendel
The study of how characteristics are transmitted from parents to offspring is called genetics.

6. Gregor Mendel, continued
Section 1 Mendel’s Legacy
Chapter 9
Gregor Mendel, continued
Mendel’s Garden Peas
Mendel observed characteristics of pea plants.
Traits are genetically determined variants of a characteristic.
Each characteristic occurred in two contrasting traits.

7. Gregor Mendel, continued
Section 1 Mendel’s Legacy
Chapter 9
Gregor Mendel, continued
Mendel’s Methods
Mendel used cross-pollination techniques in which pollen is transferred between flowers of two different plants.

8. Chapter 9 Mendel’s Experiments
Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Experiments
Mendel bred plants for several generations that were true-breeding for specific traits and called these the P generation.
Offspring of the P generation were called the F1 generation.
Offspring of the F1 generation were called the F2 generation.

9. Three Steps of Mendel’s Experiments
Section 1 Mendel’s Legacy
Chapter 9
Three Steps of Mendel’s Experiments

10. Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Experiments

11. Mendel’s Results and Conclusions
Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Results and Conclusions
Recessive and Dominant Traits
Mendel concluded that inherited characteristics are controlled by factors that occur in pairs.
In his experiments on pea plants, one factor in a pair masked the other. The trait that masked the other was called the dominant trait. The trait that was masked was called the recessive trait.

12. Mendel’s Results and Conclusions, continued
Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Results and Conclusions, continued
The Law of Segregation
The law of segregation states that a pair of factors is segregated, or separated, during the formation of gametes.

13. Mendel’s Results and Conclusions, continued
Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Results and Conclusions, continued
The Law of Independent Assortment
The law of independent assortment states that factors for individual characteristics are distributed to gametes independent of one another.
The law of independent assortment is observed only for genes that are located on separate chromosomes or are far apart on the same chromosome.

14. Support for Mendel’s Conclusions
Section 1 Mendel’s Legacy
Chapter 9
Support for Mendel’s Conclusions
We now know that the factors that Mendel studied are alleles, or alternative forms of a gene.
One allele for each trait is passed from each parent to the offspring.

15. Section 1 Mendel’s Legacy
Chapter 9
Mendel’s Conclusions

16. Chapter 9 Objectives Section 2 Genetic Crosses
Differentiate between the genotype and the phenotype of an organism.
Explain how probability is used to predict the results of genetic crosses.
Use a Punnett square to predict the results of monohybrid and dihybrid genetic crosses.
Explain how a testcross is used to show the genotype of an individual whose phenotype expresses the dominant trait.
Differentiate a monohybrid cross from a dihybrid cross.

17. Genotype and Phenotype
Section 2 Genetic Crosses
Chapter 9
Genotype and Phenotype
The genotype is the genetic makeup of an organism.
The phenotype is the appearance of an organism.

18. Section 2 Genetic Crosses
Chapter 9
Probability
Probability is the likelihood that a specific event will occur.
A probability may be expressed as a decimal, a percentage, or a fraction.

19. Calculating Probability
Section 2 Genetic Crosses
Chapter 9
Calculating Probability

20. Predicting Results of Monohybrid Crosses
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Monohybrid Crosses
A Punnett square can be used to predict the outcome of genetic crosses.
A cross in which one characteristic is tracked is a monohybrid cross.

21. Punnett Square with Homozygous Cross
Section 2 Genetic Crosses
Chapter 9
Punnett Square with Homozygous Cross

22. Monohybrid Cross of Heterozygous Plants
Section 2 Genetic Crosses
Chapter 9
Monohybrid Cross of Heterozygous Plants

23. Chapter 9 Predicting Results of Monohybrid Crosses, continued
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Monohybrid Crosses, continued
A testcross, in which an individual of unknown genotype is crossed with a homozygous recessive individual, can be used to determine the genotype of an individual whose phenotype expresses the dominant trait.

24. Section 2 Genetic Crosses
Chapter 9
Testcross

25. Chapter 9 Predicting Results of Monohybrid Crosses, continued
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Monohybrid Crosses, continued
Complete dominance occurs when heterozygous individuals and dominant homozygous individuals are indistinguishable in phenotype.

26. Chapter 9 Predicting Results of Monohybrid Crosses, continued
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Monohybrid Crosses, continued
Incomplete dominance occurs when two or more alleles influence the phenotype and results in a phenotype intermediate between the dominant trait and the recessive trait.

27. Chapter 9 Predicting Results of Monohybrid Crosses, continued
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Monohybrid Crosses, continued
Codominance occurs when both alleles for a gene are expressed in a heterozygous offspring.

28. Predicting Results of Dihybrid Crosses
Section 2 Genetic Crosses
Chapter 9
Predicting Results of Dihybrid Crosses
A cross in which two characteristics are tracked is a dihybrid cross.

29. Section 2 Genetic Crosses
Chapter 9
Dihybrid Crosses

30. Chapter 9 Multiple Choice
Standardized Test Prep
Multiple Choice
1. What is a procedure in which an individual of unknown genotype is crossed with a homozygous recessive individual to determine the genotype of the unknown individual called?
A. a monohybrid cross
B. a dihybrid cross
C. a hybrid cross
D. a testcross

31. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
1. What is a procedure in which an individual of unknown genotype is crossed with a homozygous recessive individual to determine the genotype of the unknown individual called?
A. a monohybrid cross
B. a dihybrid cross
C. a hybrid cross
D. a testcross

32. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be?
F. 1 PP : 2 Pp : 1 pp
G. 1 pp : 3 PP
H. 3 Pp : 1 pp
J. all Pp

33. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be?
F. 1 PP : 2 Pp : 1 pp
G. 1 pp : 3 PP
H. 3 Pp : 1 pp
J. all Pp

34. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
3. Which of the following is an example of a genotype of a heterozygous individual?
A. p
B. YY
C. Zz
D. rr

35. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
3. Which of the following is an example of a genotype of a heterozygous individual?
A. p
B. YY
C. Zz
D. rr

36. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
Use the diagrams of
chromosomes below to answer the question that follows.
The single chromosome below has two genes, both of which carry a dominant allele Q and R.
4. Homologous chromosomes are chromosomes that carry genes for the same characteristics, such as eye color or hair color. Which of the chromosomes in the bottom row could not be the homologous chromosome for the single chromosome in the top row?
F. 1
G. 2
H. 3
J. 4

37. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
Use the diagrams of
chromosomes below to answer the question that follows.
The single chromosome below has two genes, both of which carry a dominant allele Q and R.
4. Homologous chromosomes are chromosomes that carry genes for the same characteristics, such as eye color or hair color. Which of the chromosomes in the bottom row could not be the homologous chromosome for the single chromosome in the top row?
F. 1
G. 2
H. 3
J. 4

38. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
5. Rr : genotype :: red :
A. F1 generation
B. heterozygote
C. phenotype
D. dominant

39. Multiple Choice, continued
Chapter 9
Standardized Test Prep
Multiple Choice, continued
5. Rr : genotype :: red :
A. F1 generation
B. heterozygote
C. phenotype
D. dominant

40. Multiple Choice, continued
Chapter 8
Standardized Test Prep
Multiple Choice, continued
Use the diagram of a
Punnett square below to answer the question that
follows.
6. The Punnett square shows the expected results of a cross between two pea plants. R and r represent the alleles for round seed and wrinkled seed traits, respectively. What would the seed texture phenotype of the plant in box 4 be?
F. round
G. Rr
H. wrinkled
J. rr

41. Multiple Choice, continued
Chapter 8
Standardized Test Prep
Multiple Choice, continued
Use the diagram of a
Punnett square below to answer the question that
follows.
6. The Punnett square shows the expected results of a cross between two pea plants. R and r represent the alleles for round seed and wrinkled seed traits, respectively. What would the seed texture phenotype of the plant in box 4 be?
F. round
G. Rr
H. wrinkled
J. rr

42. Chapter 9 Short Response
Standardized Test Prep
Short Response
Mendel was able to observe certain traits as they
were passed on by carefully controlling how the pea
plants were pollinated. Explain why Mendel began his
experiments by allowing pea plants to self-pollinate
for several generations.

43. Short Response, continued
Chapter 9
Standardized Test Prep
Short Response, continued
Mendel was able to observe certain traits as they
were passed on by carefully controlling how the pea
plants were pollinated. Explain why Mendel began his
experiments by allowing pea plants to self-pollinate
for several generations.
Answer:
Mendel wanted to ensure that the plants he was studying were true-breeding.

44. Chapter 9 Extended Response
Standardized Test Prep
Extended Response
A cross between two pea plants that have axial flowers and inflated pods gives the following offspring: 20 that have axial flowers and inflated pods, 7 with axial flowers and constricted pods, and 5 that have terminal flowers and inflated pods.
Part A Identify the most probable genotype of the two parents.
Part B Use a Punnett square to explain the results.

45. Extended Response, continued
Chapter 9
Standardized Test Prep
Extended Response, continued
Answer:
Part A The ratio of offspring phenotypes is very close to the expected ratios (9:3:3:1) of a dihybrid heterozygous cross. The most likely genotype of the parents is AaIi.
Part B The Punnett square yields 9 different genotypes and 4 phenotypes.