1. 11-1: The Work of Gregor Mendel
Called the “Father of Genetics”
Austrian monk, spent time teaching high
school age students and tended the
monastery garden.
YouTube - Mendel - From the Garden to the Genome

2. Genetics - the study of heredity
Heredity - passing on of characteristics from parents to offspring

3. Mendel used “Self-pollinating” peas to produce future offspring
Knew that each flower produces both male (sperm –found in pollen) and female (egg) gametes
Fertilized flower’s egg with its own sperm
Produced what he called “true - breeding”
Offspring would be genetically identical

4. Mendel experimented with cross-pollination.
He cut the pollen-bearing anther off of the flowers and applied pollen from different flowers to the stigma (the part that catches pollen)

6. So with cross-pollination what did Mendel expect?
A: Probably a blend of both parents.
What did he get?
A: Not really what he expected.

7. Trait – specific characteristic that varies from one individual to
Genes and Dominance
Trait – specific characteristic that varies from one individual to
the next
Important that Mendel used traits that were unambiguous
Mendel’s seven traits:
Seed coat color
Seed color
Seed shape
Pod color
Pod shape
Plant height
Flower position

8. Mendel crossed true
breeds with each other
(P generation–“parental”)
Offspring known as F1
Plants that were
products of cross
-pollination are known
as “hybrids.”
F1 generation was not a
blend of parental
characteristics.
Instead….

9. Mendel’s Monohybrid Cross – P to F1
A Punnett square, something we’ll cover in a moment.
Huh?!?....all yellow seeds!!!

10. In fact………here’s what happened with the rest of the traits.

11. 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

12. Short and tall = alleles
Mendel concluded that heredity is dictated by chemical factors called genes
(About 100 years later before Watson & Crick and the whole DNA thing)
Genes have alternate forms depending on the plant
These alternate versions of the same gene are called alleles
Plant height = gene
Short and tall = alleles
Both alleles are present.
One type (recessive) can only be expressed if the other (dominant) is not present
All these are found on chromosomes!!

13. Genes, Alleles, and Chromosomes

14. What happened to the other traits?
Mendel allowed the F1 plants to self-pollinated
The “other” (recessive) traits reappeared in the F2
He was surprized, I’m sure…

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

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

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

19. Segregation – separation of alleles
How did the alleles get separated?
Segregation – separation of alleles
Mendel suggested the alleles segregated when the gametes formed.
So every sperm or egg cell has one version (allele) for that gene
Some (50%) have allele for tall, others (50%) have allele for short

20. Law of Segregation- the 2 alleles separate when gametes are formed
Law of Independent Assortment- one trait doesn’t affect the inheritance of another (purple/white flowers has nothing to do with smooth/rough pod)

21. Genes, Alleles, and Chromosomes

22. Lab Activity Interest Grabber Tossing Coins
Section 11-2
Lab Activity
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.

23. Interest Grabber continued
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?

24. 11–2 Probability and Punnett Squares A. Genetics and Probability
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

25. 11-2: Probability and the Punnett Square
Probability – likelihood of an event to take place
What are the chances for a coin to be flipped heads three times in a row?
½ X ½ X ½ = ⅛
Probability explains everything in predicting outcomes of genetic crosses.

26. Punnett Squares
Possible gene combinations are represented showing a Punnett Square.
Homozygous – same allele (SS or ss)
Heterozygous - different allele (Ss)
Genotype – genetic makeup (SS, Ss, ss)
Phenotype – physical feature observed (Smooth, wrinkled)

34. Probability and Segregation
Characters investigated by Mendel
Consistency is Good
No matter what the characteristic, Mendel observed a 3:1 ratio of characteristics in the F2.

35. Monohybrid Crosses Yielded Consistent Results
Therefore, the Principle of Segregation indeed is a general principle of genetics.

36. Probabilities Predict Averages
The more times you flip a coin, the closer it will be to the expected result
Consequently the more offspring that an organism has, the closer the results will be to the averages.
This is why scientists perform MANY experiments.
Avoid the small percentage event and assume it is the trend.

37. Interest Grabber Height in Humans
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?

38. Interest Grabber continued
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.

39. 11–3 Exploring Mendelian Genetics A. Independent Assortment
Section Outline
Section 11-3
11–3 Exploring Mendelian Genetics
A. Independent Assortment
1. The Two-Factor Cross: F1
2. The Two-Factor Cross: F2
B. A Summary of Mendel’s Principles
C. Beyond Dominant and Recessive Alleles
1. Incomplete Dominance
2. Codominance
3. Multiple Alleles
4. Polygenic Traits
D. Applying Mendel’s Principles
E. Genetics and the Environment

40. Independent Assortment
Mendel wondered if alleles for separate genes influenced each other when they segregate.
Ex: Does a round seed always have to be yellow, or can it be green?
Two-factor cross
Followed two separate genes from generation to generation
Independent Assortment of Alleles

41. Two Factor Cross
Crossed true bred round/yellow (RRYY) pea plants with wrinkled/green (rryy) plants
F1 – 100% round/yellow (RrYy)
No surprise to Mendel
Mendel hypothesized there was dependent assortment, therefore predicted 3:1 ratio in the F2 (just like in the first experiment)
3 round/yellow : 1 wrinkled/green

43. Fig. 10.12a Dihybrid cross: F1 generation

44. Fig. 10.12b Dihybrid cross: F2 generation Ratio: 9:3:3:1

45. Beyond dominance and recessiveness
Incomplete dominance
Hybrids (heterozygous) exhibit blend of traits
4 o’clock plants
Red and white produce heterozygous pink plants

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

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

48. Chickens with speckled black spots on white feathers
Codominance
MOO
Similar to incomplete dominance however both traits are actually visual instead of blended
Chickens with speckled black spots on white feathers
Humans have gene for protein controlling cholesterol – if heterozygous two forms are made.

49. When there are more than two alleles for a particular gene
Multiple Alleles
When there are more than two alleles for a particular gene
Blood type (also demonstrates some codominance)
Polygenic traits
Traits controlled by many genes
Height
SLE (Lupus)
Weight
Eye Color
Intelligence
Skin Color
Many forms of behavior

53. Applying Mendel’s Principles
Good animal to test was fruit fly
Drosophilia melanogaster
Fast reproductive rate/life cycle and produced many offspring

55. Environmental impact on gene expression
                       
Environmental factors/conditions may alter gene expression.
Example: Soil pH and flower color.

56. Hydranga

57. How Many Chromosomes? Interest Grabber
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.

58. 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?

59. 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

60. Process of turning diploid somatic cells into haploid gametes
11-4 Meiosis
Process of turning diploid somatic cells into haploid gametes
Must reduce chromosome number so when fertilization takes place we re-establish the regular chromosome number
Humans
Hapolid – sex cells N = 23
Diploid – somatic cells 2N = 46
N = chromosome number

63. Phases of meiosis
Meiosis I and II

66. Figure Meiosis
Section 11-4
Meiosis I

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

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

69. Figure Meiosis
Section 11-4
Meiosis I

70. Figure Meiosis
Section 11-4
Meiosis I

71. 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.

72. 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.

73. 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.

74. 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.

75. 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.

76. Crossing over
Parts of chromosomes “switch places”
Meiosis

77. Crossing-Over
Section 11-4

78. Crossing-Over
Section 11-4

79. Crossing-Over
Section 11-4

80. Mitosis vs. meiosis

81. 11–5 Linkage and Gene Maps A. Gene Linkage B. Gene Maps
Section Outline
Section 11-5
11–5 Linkage and Gene Maps
A. Gene Linkage
B. Gene Maps

82. 11-5: Linkage and Gene Maps
Found that some genes were linked to other ones
Seems to violate the rule of independent assortment
Ex: fruit flies – red eyes and minature wings

83. Mendel missed this….
He thought the genes independently assorted
Actually it was the chromosomes that do!
Why did he miss it?
6 of the 7 genes he studied in peas were on separate chromosomes
The two that were on the same chromosome were so far apart they independently assorted

84. Gene Map
Do two genes on the same chromosome mean they are forever linked?
No! Crossing over may put them on separate chromosomes
The further apart genes are the more likely they could be separated during meiosis
Low rate of separation and then recombination means genes are close to one another.

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