1. Analyzing Inheritance
Section 11-1
Analyzing Inheritance
Offspring resemble their parents. Offspring inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals.
In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.

2. Section 11-1
Parents
Long stems  short stems
Red flowers  white flowers
Green pods  yellow pods
Round seeds  wrinkled seeds
Yellow seeds  green seeds
First Generation
All long
All red
All green
All round
All yellow
Second Generation
787 long: 277 short
705 red: 224 white
428 green: 152 yellow
5474 round: 1850 wrinkled
6022 yellow: 2001 green
1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
2. How do the characteristics of the second generation compare to the characteristics of the first generation?

3. 11–1 The Work of Mendel A. Gregor Mendel’s Peas B. Genes and Dominance
Section Outline
Section 11-1
11–1 The Work of Mendel
A. Gregor Mendel’s Peas
B. Genes and Dominance
C. Segregation
1. The F1 Cross
2. Explaining the F1 Cross

4. Section 11-1
11–1 The Work of Mendel
Gregor Mendel ( ) was a monk at a monastery in Brunn, Austria
He taught school and did other chores, but in his spare time he set out to study plant breeding
He started breeding pea plants about 1855
He wanted to learn the rules of heredity so that better varieties could be produced

5. 11–1 cont. Mendel’s original pea plants were true-breeding.
Section 11-1
11–1 cont.
Mendel’s original pea plants were true-breeding.
When allowed to self-pollinate they produced offspring identical to themselves
Mendel wanted to cross-pollinate the plants and study the results
Mendel studied seven different pea plant traits (specific characteristic that varies from individual to individual) with 2 contrasting characteristics

6. Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants
Section 11-1
Seed Shape
Seed Color
Seed Coat
Color
Pod
Shape
Pod Color
Flower Position
Plant Height
Round
Yellow
Gray
Smooth
Green
Axial
Tall
Wrinkled
Green
White
Constricted
Yellow
Terminal
Short
Round
Yellow
Gray
Smooth
Green
Axial
Tall

7. 11–1 cont. Mendel called each original pair of plants the
Section 11-1
11–1 cont.
Mendel called each original pair of plants the
P Generation (parental) and the offspring of these the F1 generation (first filial)
Mendel produced hybrids when he crossed parents with different traits; and to his surprise the offspring only resembled one of the parents

8. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

9. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

10. 11–1 cont. Mendel drew 2 conclusions from this experiment:
Section 11-1
11–1 cont.
Mendel drew 2 conclusions from this experiment:
Biological inheritance is determined by factors that are passed from one generation to the next; today known as genes
Principle of Dominance which states that some alleles (different forms of a gene) are dominant and others are recessive

11. Section 11-1
11–1 cont.
Dominant alleles will always exhibit that form of the trait and is represented with a capital letter
ex. (T) - Tall
Recessive alleles will only exhibit that form of the trait if the dominant allele is not present and is represented with a lower case letter
ex. (t) - short

12. Section 11-1
11–1 cont.
Mendel then allowed his F1 hybrid plants to self-pollinate to produce an F2 generation (second filial)
Traits controlled by the recessive alleles reappeared in ¼ of the F2 generation
Mendel explained that the dominant allele masked the recessive allele in the F1 generation and due to the segregation of alleles during gamete formation reappeared in the F2 generation

13. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short

14. Section 11-1
T t
F1 Generation T t
Gametes
T T
T t
t t F2
Generation

15. Section 11-2
Tossing Coins
If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

16. 4. How do the expected results differ from the observed results?
Section 11-2
1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?
2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?
3. If you compiled the results for the whole class, what results would you expect?
4. How do the expected results differ from the observed results?

17. 11–2 Probability and Punnett Squares
Section Outline
Section 11-2
11–2 Probability and Punnett Squares
A. Genetics and Probability
B. Punnett Squares
C. Probability and Segregation
D. Probabilities Predict Averages

18. 11–2 Probability and Punnett Squares
Section 11-2
11–2 Probability and Punnett Squares
Probability is the likelihood that a particular event will occur and Mendel realized that the principles of probability could be used in predicting the outcomes of genetic crosses

19. Section 11-2
11–2 cont.
Punnett Squares can be used to predict and compare the genetic variations that will result from a cross
The gametes are shown along the top and left side
Possible gene combinations of the offsping appear in the boxes

20. Tt X Tt Cross
Section 11-2

21. Tt X Tt Cross
Section 11-2

22. Section 11-2
11–2 cont.
Homozygous organisms are true-breeding which means they have two identical alleles for a particular trait
Ex. TT
Heterozygous organisms are hybrids that have two different alleles for the same trait
Ex. Tt

23. 11–2 cont. Genotype vs. Phenotype
Section 11-2
11–2 cont.
Genotype vs. Phenotype
The genotype is the actual genetic makeup of the traits, while the phenotype is the actual physical characteristics of an organism

24. 11–3 Exploring Mendelian Genetics
Section Outline
Section 11-3
11–3 Exploring Mendelian Genetics
A. Independent Assortment
1. The Two-Factor Cross: F The Two-Factor Cross: F2
B. A Summary of Mendel’s Principles
C. Beyond Dominant and Recessive Alleles
1. Incomplete Dominance Codominance
3. Multiple Alleles Polygenic Traits
D. Applying Mendel’s Principles
E. Genetics and the Environment

25. 11-3 Exploring Mendelian Genetics
After proving that alleles segregate in the formation of gametes, Mendel wanted to know if they did so independently – did the segregation of one pair of alleles affect the segregation of other pairs?
Two-Factor Cross – F1
- Mendel crossed homozygous round yellow peas (RRYY) with wrinkled green peas (rryy).
- F1 were all round yellow (RrYy)

26. Two-Factor – F2
- Mendel knew F1’s were heterozygous for both traits
- when allowed to self-fertilize the F1 gave rise to F2’s w/ a
definite ratio
- this led Mendel to his Principle of Independent Assortment
- alleles for different characteristics segregate independently of
each other – so as long as genes for two traits are on
different chromosomes every combination of alleles is possible.

27. Figure 11-10 Independent Assortment in Peas
Section 11-3

28. Concept Map Gregor Mendel Pea plants “Factors” determine traits Law of
Section 11-3
Gregor
Mendel
experimented with
concluded that
Pea
plants
“Factors”
determine
traits
Some alleles
are dominant,
and some alleles
are recessive
Alleles are
separated during
gamete formation
which is called the
which is called the
Law of
Dominance
Segregation

29. Incomplete Dominance * when neither allele is dominant over the other
- heterozygotes differ phenotypically from either
homozygote
Ex.: Four O’clock plants
- RR = red
- WW = white
- RW = pink
** this is not blending because red and white
flowers will reappear.

30. Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Section 11-3

31. Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
Section 11-3

32. Codominance
* situation in which both alleles contribute to the phenotype
- both are expressed if present
Ex.: chickens – white and black feathers are codominant
- heterozygotes produce both white and black feathers
** A and B alleles in human blood types

33. Multiple Alleles * when a gene has more than two alleles
- each individual still only gets two of the possible alleles that exist in the population
Ex.: Human blood groups
- three alleles = A, B, O
- A and B are codominant
- O is recessive

34. Polygenic Traits * traits which are influenced by several genes
- results in a wide range of phenotypes
Ex.: Human height, skin color, color in eyes of fruitflies

35. Section 11-3
Height in Humans
Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the recessive one. What about people? Are the factors that determine height more complicated in humans?

36. 2. What can you observe about the heights of the ten people?
Section 11-3
1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.
2. What can you observe about the heights of the ten people?
3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.

37. Applying Mendel’s Principles
* Mendel’s principles apply to all organisms
- Thomas Hunt Morgan – began use of fruitflies
- ideal organism
- fast breeder
- lots of young
- many observable traits
- small size
- Environment also affects development of organisms

38. Sex Linkage - genes located on autosomes behave as we have studied
- genes located on the sex chromosomes often exhibit a unique
pattern of inheritance.
- in mammals females have two X-chromosomes (XX)
- in mammals males have an X and a Y chromosome (XY)
- the Y chromosome has a gene (SRY) that makes the
embryo male
- but Y has fewer genes than X and so males only get one
copy of some genes on the Y
- genes that males only get one copy of are sex-linked and are
expressed more often in males than females
- color-blindness, muscular dystrophy

39. D. Comparing Mitosis and Meiosis
Section Outline
Section 11-4
11–4 Meiosis
A. Chromosome Number
B. Phases of Meiosis
1. Meiosis I
2. Meiosis II
C. Gamete Formation
D. Comparing Mitosis and Meiosis

43. Interest Grabber How Many Chromosomes?
Section 11-4
How Many Chromosomes?
Normal human body cells each contain 46 chromosomes. The cell division process that body cells undergo is called mitosis and produces daughter cells that are virtually identical to the parent cell. Working with a partner, discuss and answer the questions that follow.

45. Interest Grabber continued
Section 11-4
1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?

46. Crossing-Over
Section 11-4

47. Crossing-Over
Section 11-4

48. Crossing-Over
Section 11-4

50. Figure Meiosis
Section 11-4
Meiosis I

51. Figure Meiosis
Section 11-4
Meiosis I
Meiosis I

52. Figure Meiosis
Section 11-4
Meiosis I
Meiosis I

53. Figure Meiosis
Section 11-4
Meiosis I

54. Figure Meiosis
Section 11-4
Meiosis I

55. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

56. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

57. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

58. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

59. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

60. Interest Grabber Forever Linked?
Section 11-5
Forever Linked?
Some genes appear to be inherited together, or “linked.” If two genes
are found on the same chromosome, does it mean they are linked forever?
Study the diagram, which shows four genes labeled A–E and a–e, and then answer the questions on the next slide.

61. Interest Grabber continued
Section 11-5
1. In how many places can crossing over result in genes A and b being on the same chromosome?
2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?
3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?

62. Section Outline 11–5 Linkage and Gene Maps A. Gene Linkage
B. Gene Maps

63. Comparative Scale of a Gene Map
Section 11-5
Mapping of Earth’s Features
Mapping of Cells, Chromosomes, and Genes
Cell
Earth
Country
Chromosome
Chromosome fragment
State
Gene
City
People
Nucleotide base pairs

64. Figure 11-19 Gene Map of the Fruit Fly
Section 11-5
Exact location on chromosomes
Chromosome 2

65. Click a hyperlink to choose a video. Meiosis Overview
Videos
Click a hyperlink to choose a video.
Meiosis Overview
Animal Cell Meiosis, Part 1
Animal Cell Meiosis, Part 2
Segregation of Chromosomes
Crossing Over
Video Contents

66. Click the image to play the video segment.
Meiosis Overview
Click the image to play the video segment.
Video 1

67. Click the image to play the video segment.
Animal Cell Meiosis, Part 1
Click the image to play the video segment.
Video 2

68. Click the image to play the video segment.
Animal Cell Meiosis, Part 2
Click the image to play the video segment.
Video 3

69. Click the image to play the video segment.
Segregation of Chromosomes
Click the image to play the video segment.
Video 4

70. Click the image to play the video segment.
Crossing Over
Click the image to play the video segment.
Video 5

71. Go Online The latest discoveries in genetics Interactive test
Articles on genetics
For links on Punnett squares, go to and enter the Web Code as follows: cbn-4112.
For links on Mendelian genetics, go to and enter the Web Code as follows: cbn-4113.
For links on meiosis, go to and enter the Web Code as follows: cbn-4114.
Internet

72. Interest Grabber Answers
1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
All offspring had the same characteristic, which was like one of the parents’. The other characteristic seemed to have disappeared.
2. How do the characteristics of the second generation compare to the characteristics of the first generation?
Both characteristics appeared in this generation. The characteristic that had “disappeared” in the first generation did not appear as often as the other characteristic. (It appears about 25 percent of the time.)
Section 1 Answers

73. Interest Grabber Answers
1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected?
Results will vary, but should be close to 5 heads and 5 tails.
2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected?
The results for 20 tosses may be closer to the predicted 10 heads and 10 tails.
3. If you compiled the results for the whole class, what results would you expect?
The results for the entire class should be even closer to the number predicted by the rules of probability.
4. How do the expected results differ from the observed results?
The observed results are usually slightly different from the expected results.
Section 2 Answers

74. Interest Grabber Answers
1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.
Check students’ answers to make sure they are realistic.
2. What can you observe about the heights of the ten people?
Students should notice that there is a range of heights in humans.
3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.
No, height does not seem to be controlled by two alleles, as it is in pea plants. Height in humans can vary greatly and is not just found in tall and short phenotypes.
Section 3 Answers

75. Interest Grabber Answers
1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
46 chromosomes
2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
= 92; a developing embryo would not survive if it contained 92 chromosomes.
3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
Sperm and egg should each have 23 chromosomes.
Section 4 Answers

76. Interest Grabber Answers
1. In how many places can crossing over result in genes A and b being on the same chromosome?
One (between A and B)
2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?
Two (between A and B and A and C); Four (between A and B, A and C, A and D, and A and E)
3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?
The farther apart the genes are, the more likely they are to be recombined through crossing over.
Section 5 Answers

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