1. Test Crosses and Probability

2. Test Cross
breeding an individual whose phenotype is known but whose genotype is unknown to an individual with a homozygous recessive genotype
can be used to determine the first individual’s genotype

3. Test Cross Example
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?

4. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Identification of Alleles P = purple p = white Parent Genotype Identification Purple parent: P? White parent: pp

5. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? p p

6. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? Pp p p

7. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? Pp p p p

8. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? Pp p p p

9. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? Pp p p p

10. Genotype of Purple Parent
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Genotype of Purple Parent

11. A purple-flowered plant is crossed with a white-flowered plant
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Punnett Square P ? Pp p p p

12. Test Cross Example Punnett SquarePp pp p p

13. Genotype of Purple Parent Pp Heterozygous
A purple-flowered plant is crossed with a white-flowered plant. Some of the plants in the next generation produce purple flowers and some produce white flowers. What is the genotype of the purple-flowered plant?
Genotype of Purple Parent Pp Heterozygous

14. total # of possible outcomes
Probability
the likelihood (“chance” or “odds”) that a specific event will occur
can be expressed as words, percents, or fractions
the chance of flipping a heads on a coin is: 1/2
Probability =
# of one kind of outcome
total # of possible outcomes

15. Probability Example
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?

16. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Identification of Alleles P = purple p = white Parent Genotype Identification Heterozygous parent 1: Pp Heterozygous parent 2: Pp

17. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p P p

18. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p PP P p

19. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p PP Pp P p

20. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p PP Pp P p

21. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p PP Pp pp P p

22. Probability of White Offspring
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Probability of White Offspring

23. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Punnett Square P p PP Pp pp P p

24. Probability of White Offspring 1/4
Two heterozygous purple-flowered plants are crossed. What is the probability that they will have a white-flowered offspring?
Probability of White Offspring 1/4

25. Multiple Events Probability
calculate the probability of two or more things happening in a row by multiplying the probability of each event occurring on its own
Probability of flipping a heads:

26. Multiple Events Probability
calculate the probability of two or more things happening in a row by multiplying the probability of each event occurring on its own
Probability of flipping a heads: 1/2
Probability of flipping a tails:

27. Multiple Events Probability
calculate the probability of two or more things happening in a row by multiplying the probability of each event occurring on its own
Probability of flipping a heads: 1/2
Probability of flipping a tails: 1/2
Probability of flipping a heads and then a tails:

28. Multiple Events Probability
calculate the probability of two or more things happening in a row by multiplying the probability of each event occurring on its own
Probability of flipping a heads: 1/2
Probability of flipping a tails: 1/2
Probability of flipping a heads and then a tails: 1/2 * 1/2 = 1/4

29. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they produce a white-flowered offspring and then produce a purple-flowered offspring?
Identification of Alleles P = purple p = white Parent Genotype Identification Heterozygous parent 1: Pp Heterozygous parent 2: Pp

30. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they produce a white-flowered offspring and then produce a purple-flowered offspring?
Punnett Square P p PP Pp pp P p

31. Multiple Events Probability Example
White
Flower
Probability

32. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they produce a white-flowered offspring and then produce a purple-flowered offspring?
Punnett Square P p PP Pp pp P p

33. Multiple Events Probability Example
White
Flower
Probability
Purple 1 4

34. Two heterozygous purple-flowered plants are crossed
Two heterozygous purple-flowered plants are crossed. What is the probability that they produce a white-flowered offspring and then produce a purple-flowered offspring?
Punnett Square P p PP Pp pp P p

35. Multiple Events Probability Example
White
Flower
Probability
Purple
Probability of Getting BOTH 1 3 4

36. Multiple Events Probability Example
White
Flower
Probability
Purple
Probability of Getting BOTH 1 * 3 = 4

37. Multiple Events Probability Example
White
Flower
Probability
Purple
Probability of Getting BOTH 1 * 3 = 4 16

38. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Identification of Alleles L = long stems l = short stems Parent Genotype Identification Long stem parent: L? Short stem parent: ll

39. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? l l

40. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l

41. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l l

42. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l l

43. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l l

44. Long stem Plant Genotype
In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Long stem Plant Genotype

45. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l l

46. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L ? Ll l l

47. In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Punnett Square L L Ll l l

48. Long stem Plant Genotype LL Homozygous dominant
In garden peas, long stems (L) are dominant and short stems (l) are recessive. A long plant is crossed with a short plant. This is a test cross to determine the genotype of the long plant. If all of the offspring produced in this test cross are also long plants, what was the genotype of the parental long stem plant?
Long stem Plant Genotype LL Homozygous dominant

49. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Identification of Alleles L = long stems l = short stems Parent Genotype Identification Ll ll

50. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l l l

51. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l Ll l l

52. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l Ll ll l l

53. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l Ll ll l l

54. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l Ll ll l l

55. Short Stemmed Offspring Probability
If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Short Stemmed Offspring Probability

56. If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Punnett Square L l Ll ll l l

57. Short Stemmed Offspring Probability 2/4
If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Short Stemmed Offspring Probability 2/4

58. Simplify fractions if possible.

59. Short Stemmed Offspring Probability 2/4
If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Short Stemmed Offspring Probability 2/4

60. Short Stemmed Offspring Probability 2/4 1/2 or 50%
If a heterozygous long stem plant (L) is crossed with a homozygous recessive short stem plant (l), what is the probability that their offspring will be short stemmed? You may report your answer in a fraction or a percent.
Short Stemmed Offspring Probability 2/4 1/2 or 50%

61. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Identification of Alleles I = inflated pods i = constricted pods Parent Genotype Identification Inflated parent: I? Constricted parent: ii

62. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? i i

63. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i

64. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i

65. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i i

66. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i i

67. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i i

68. Inflated Pods Parent Genotype
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Inflated Pods Parent Genotype

69. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i i

70. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I ? Ii i i

71. In garden peas, inflated (I) pods are dominant to constricted pods (i)
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Punnett Square I I Ii i i

72. Inflated Pods Parent Genotype II Homozygous dominant
In garden peas, inflated (I) pods are dominant to constricted pods (i). A plant that has inflated pods is crossed with a plant that has constricted pods in a test cross. If all of the offspring produced from this cross have inflated pods, what was the genotype of the parental plant with inflated pods?
Inflated Pods Parent Genotype II Homozygous dominant

73. Identification of Alleles Parent Genotype Identification
In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Identification of Alleles Parent Genotype Identification

74. The Work of Gregor Mendel (a little background information…)
Holt Biology, pg. 163

75. In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Identification of Alleles A = axial flowers a = terminal flowers Parent Genotype Identification AA aa

76. In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Punnett Square A A a a

77. In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Punnett Square A A Aa a a

78. In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Probability of Producing an Axial Offspring followed by a Terminal Offspring

79. Multiple Events Probability Example
Axial
Flower
Probability
Terminal
Probability of Getting BOTH 4

80. Multiple Events Probability Example
Axial
Flower
Probability
Terminal
Probability of Getting BOTH 4 * =

81. Multiple Events Probability Example
Axial
Flower
Probability
Terminal
Probability of Getting BOTH 4 * = 16

82. Simplify fractions if possible.

83. In garden peas, axial flowers are dominant and terminal flowers are recessive. In a cross between two homozygous plants, one that has axial flowers and one that has terminal flowers, what will be the probability that they produce an axial offspring then a terminal offspring?
Probability of Producing an Axial Offspring followed by a Terminal Offspring 0