1. Patterns of Inheritance
Beyond Dominant and Recessive

2. What we have learned up to this point is called complete dominance.

3. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.

4. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.
For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?

5. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.
For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?
BB:
Bb:
bb:

6. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.
For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?
BB: Brown
Bb:
bb:

7. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.
For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?
BB: Brown
Bb: Brown
bb:

8. What we have learned up to this point is called complete dominance.
With complete dominance, the heterozygote shows the dominant phenotype.
For example, brown (B) is dominant to white (b). Based on what we learned, what are the phenotypes of the following genotypes?
BB: Brown
Bb: Brown
bb: White

9. This isn’t always the case
This isn’t always the case. These new types of inheritance are all EXCEPTIONS to complete dominance.

10. Incomplete Dominance
The heterozygote displays an intermediate phenotype that is a blending of the dominant and recessive phenotypes.

12. Incomplete Dominance
Example: Snap dragons
RR =
rr =
Rr =

13. Incomplete Dominance
Example: Snap dragons
RR = Red flowers
rr =
Rr =

14. Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr =

15. Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers

16. Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers
Genotypic Ratio:
Phenotypic Ratio:

17. Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio:

18. Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio: R r

19. RR Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio: RR R r

20. RR Rr Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio: RR Rr R r

21. RR Rr Rr Incomplete Dominance Example: Snap dragons RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio: RR Rr R Rr r

22. RR Rr Rr rr Incomplete Dominance Example: Snap dragons
RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
Phenotypic Ratio: RR Rr R Rr rr r

23. RR Rr Rr rr Incomplete Dominance Example: Snap dragons
RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
1:2:1
Phenotypic Ratio: RR Rr R Rr rr r

24. RR Rr Rr rr Incomplete Dominance Example: Snap dragons
RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
1:2:1
Homozygous Dom.: Heterozygous: Homozygous Rec.
Phenotypic Ratio: RR Rr R Rr rr r

25. RR Rr Rr rr Incomplete Dominance Example: Snap dragons
RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
1:2:1
Homozygous Dom.: Heterozygous: Homozygous Rec.
Phenotypic Ratio: RR Rr R Rr rr r

26. RR Rr Rr rr Incomplete Dominance Example: Snap dragons
RR = Red flowers
rr = White flowers
Rr = Pink flowers R r
Genotypic Ratio:
1:2:1
Homozygous Dom.: Heterozygous: Homozygous Rec.
Phenotypic Ratio:
Red: Pink: White RR Rr R Rr rr r

27. Codominance
The heterozygote displays the phenotype of both of the alleles it possesses
Both alleles act as dominant alleles and show up independently (such as with spots)
Remember co- means together, so in codominance the heterozygote shows both traits together.

29. Codominance
Example: Roan Coat Color in Cows
RR =
WW =
RW =

30. Codominance
Example: Roan Coat Color in Cows
RR = Brown coat
WW =
RW =

31. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW =

32. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW = Roan coat

33. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW = Roan coat
All capital letters!

34. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
Phenotypic Ratio:
All capital letters!

35. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
Phenotypic Ratio: R W
All capital letters!

36. Codominance Example: Roan Coat Color in Cows RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
Phenotypic Ratio: R W R
All capital letters! W

37. RR RW RW WW Codominance Example: Roan Coat Color in Cows
RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
Phenotypic Ratio: R W RR RW R
All capital letters! RW WW W

38. RR RW RW WW Codominance Example: Roan Coat Color in Cows
RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
1:2:1
Phenotypic Ratio: R W RR RW R
All capital letters! RW WW W

39. RR RW RW WW Codominance Example: Roan Coat Color in Cows
RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
1:2:1
RR:RW:WW
Phenotypic Ratio: R W RR RW R
All capital letters! RW WW W

40. RR RW RW WW Codominance Example: Roan Coat Color in Cows
RR = Brown coat
WW = White coat
RW = Roan coat
Genotypic Ratio:
1:2:1
RR:RW:WW
Phenotypic Ratio: R W RR RW R
All capital letters! RW WW W

41. RR RW RW WW Codominance Example: Roan Coat Color in Cows
RR = Brown coat
WW = White coat
RW = Roan
Genotypic Ratio:
1:2:1
RR:RW:WW
Phenotypic Ratio:
Brown: Roan: White R W RR RW R
All capital letters! RW WW W

42. Multiple Alleles

43. Multiple Alleles
A gene that has three or more genes

44. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups

45. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): , ,
, and

46. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , ,
, and

47. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
, and

48. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and

49. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and O

50. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and O
Blood type is controlled by three alleles: , , or

51. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and O
Blood type is controlled by three alleles: A , , or

52. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and O
Blood type is controlled by three alleles: A , B , or

53. Multiple Alleles A gene that has three or more genes
Example: Human ABO Blood Groups
In humans, there are four blood types (phenotypes): A , B ,
AB , and O
Blood type is controlled by three alleles: A , B , or O

54. Multiple Alleles
These alleles code for types of carbohydrates that are on the surface of the red blood cells. Allele A codes for A type carbohydrates. Allele B codes for B type carbohydrates. Allele O codes for no carbohydrates.
The O allele is recessive. Two O alleles must be present for the person to have O type blood.

55. Multiple Alleles
The A and B alleles are codominant. If a person receives an A allele and a B allele, their blood type is AB. The AB blood cells have both A and B type carbohydrates.

56. Multiple Alleles
Phenotype
Genotypes A B AB O

57. Multiple Alleles
Phenotype
Genotypes A AA B AB O

58. Multiple Alleles
Phenotype
Genotypes A
AA, AO B AB O

59. Multiple Alleles
Phenotype
Genotypes A
AA, AO B BB AB O

60. Multiple Alleles
Phenotype
Genotypes A
AA, AO B
BB, BO AB O

61. Multiple Alleles
Phenotype
Genotypes A
AA, AO B
BB, BO AB O

62. Multiple Alleles
Phenotype
Genotypes A
AA, AO B
BB, BO AB O OO

63. Multiple Alleles
AB x AB
Genotypic Ratio:
Phenotypic Ratio:

64. Multiple Alleles
AB x AB A B
Genotypic Ratio:
Phenotypic Ratio: A B

65. Multiple Alleles AB x AB A B Genotypic Ratio: Phenotypic Ratio: AA ABBB B

66. Multiple Alleles AB x AB A B Genotypic Ratio: 1:2:1 AA:AB:BB
Phenotypic Ratio: AA AB A AB BB B

67. Multiple Alleles AB x AB A B Genotypic Ratio: 1:2:1 AA:AB:BB
Phenotypic Ratio:
A:AB:B AA AB A AB BB B

68. Multiple Alleles
AO x BO
Genotypic Ratio:
Phenotypic Ratio:

69. Multiple Alleles
AO x BO A O
Genotypic Ratio:
Phenotypic Ratio: B O

70. Multiple Alleles AO x BO A O Genotypic Ratio: Phenotypic Ratio: AB BOOO O

71. Multiple Alleles AO x BO A O Genotypic Ratio: 1:1:1:1 AB:BO:AO:OO
Phenotypic Ratio: AB BO B AO OO O

72. Multiple Alleles AO x BO A O Genotypic Ratio: 1:1:1:1 AB:BO:AO:OO
Phenotypic Ratio:
AB:B:A:O AB BO B AO OO O

73. Polygenic Traits Traits controlled by 2 or more genes
Usually see a lot of possible phenotypes
Examples: Height, eye color

75. Plietropy A single gene affects more than one trait Sick cell anemia
Affects the shape of the blood cells
Causes heart damage
Causes brain damage
Weakness

76. Epistasis One gene impacts the expression of another gene
Example: Albinism
The recessive genotype for albinism (aa) masks the genes for eye and hair color.
As a result, albinos have white hair and pink eyes.

78. Environmental Effects
The environment can influence the phenotype of an organism
Example: Arctic fox
In the summer, the fox is brown because its DNA codes for brown pigments.
In the winter, the enzyme does not function because it’s too cold. The fox becomes white.

79. Summer
Winter

80. Sex-Linked Genes

81. Sex-Linked Genes
Genes located on the X-chromosome

82. Sex-Linked Genes Genes located on the X-chromosome
Remember organisms have (chromosomes that do not determine an organism’s sex) and (chromosomes that DO determine an organism’s sex)

83. Sex-Linked Genes Genes located on the X-chromosome
Remember organisms have autosomes (chromosomes that do not determine an organism’s sex) and (chromosomes that DO determine an organism’s sex)

84. Sex-Linked Genes Genes located on the X-chromosome
Remember organisms have autosomes (chromosomes that do not determine an organism’s sex) and sex chromosomes (chromosomes that DO determine an organism’s sex)

85. Sex-Linked Genes
Females have as their sex chromosomes and males have

86. Sex-Linked Genes
Females have XX as their sex chromosomes and males have

87. Sex-Linked Genes
Females have XX as their sex chromosomes and males have XY

88. Sex-Linked Genes
Females have XX as their sex chromosomes and males have XY
Because males only have 1 X chromosome, they only need one recessive allele to show the recessive phenotype.

89. Sex-Linked Genes
Females have XX as their sex chromosomes and males have XY
Because males only have 1 X chromosome, they only need one recessive allele to show the recessive phenotype.
A female who has a recessive allele on only one X chromosome will not display the recessive phenotype.

90. Sex-Linked Genes Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
Phenotypic Ratio
Genotypic Ratio

91. Sex-Linked Genes XN Xn x XNY Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY
Phenotypic Ratio
Genotypic Ratio

92. Sex-Linked Genes XN Xn x XNY XN Xn Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY XN Xn
Phenotypic Ratio
Genotypic Ratio

93. Sex-Linked Genes XN Xn x XNY XN Xn XN Y
Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY XN Xn
Phenotypic Ratio
Genotypic Ratio XN Y

94. Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y
Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY XN Xn
Phenotypic Ratio
Genotypic Ratio XN XN Xn XN XN Y Xn Y XN Y

95. Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y
Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY XN Xn
Phenotypic Ratio
1:1:1:1
Colorblind female: Normal female: Colorblind male: Normal male
Genotypic Ratio XN XN Xn XN XN Y Xn Y XN Y

96. Sex-Linked Genes XN Xn x XNY XN Xn XN XN Xn XN XN Y Xn Y XN Y
Example: Red-Green Color Blindness
Normal vision, XN, is dominant to colorblindness, Xn.
XN Xn x XNY XN Xn
Phenotypic Ratio
1:1:1:1
Colorblind female: Normal female: Colorblind male: Normal male
Genotypic Ratio
XNXN:XNXn:XNY:XnY XN XN Xn XN XN Y Xn Y XN Y

97. Pedigree
Family tree that traces the inheritance of traits through many generations
Symbols:
Normal
Affected
Male
Female

98. I II Pedigree Mating Generations I1 II3
Names are determined by giving the generation number and the number they are in the row, counting left to right.
Children from mating

99. Pedigree
Carrier-

100. Pedigree
Carrier- an individual who carries a recessive gene but is unaffected by the gene

101. Pedigree
Carrier- an individual who carries a recessive gene but is unaffected by the gene
Pedigree problems have you determine the pattern of inheritance of a gene (dominant or recessive, autosomal or sex-linked) within a family.

102. Pedigree
Carrier- an individual who carries a recessive gene but is unaffected by the gene
Pedigree problems have you determine the pattern of inheritance of a gene (dominant or recessive, autosomal or sex-linked) within a family.
To do these problems, there are three steps you should follow.

103. 1. Determining if a trait is dominant or recessive.

104. 1. Determining if a trait is dominant or recessive.
Common patterns of dominant traits:

105. 1. Determining if a trait is dominant or recessive.
Common patterns of dominant traits:
Vertical patterns of inheritance meaning that there is an infected individual in each generation.

106. 1. Determining if a trait is dominant or recessive.
Common patterns of dominant traits:
Vertical patterns of inheritance meaning that there is an infected individual in each generation.

107. 1. Determining if a trait is dominant or recessive.

108. 1. Determining if a trait is dominant or recessive.
Common patterns of recessive traits:

109. 1. Determining if a trait is dominant or recessive.
Common patterns of recessive traits:
Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation

110. 1. Determining if a trait is dominant or recessive.
Common patterns of recessive traits:
Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation
Often skips generations so the trait may appear after several generations of unaffected individuals

111. 1. Determining if a trait is dominant or recessive.
Common patterns of recessive traits:
Horizontal patterns of inheritance meaning that there usually are multiple affected individuals within an generation
Often skips generations so the trait may appear after several generations of unaffected individuals

112. 2. Determining if a trait is autosomal or sex-linked

113. 2. Determining if a trait is autosomal or sex-linked
Common characteristics of a sex-linked recessive gene

114. 2. Determining if a trait is autosomal or sex-linked
Common characteristics of a sex-linked recessive gene
Occurs more often in males than females

115. 2. Determining if a trait is autosomal or sex-linked
Common characteristics of a sex-linked recessive gene
Occurs more often in males than females
Often skips generations through female carriers (heterozygotes). All of the daughters of affected males are carriers.

116. 2. Determining if a trait is autosomal or sex-linked
Common characteristics of a sex-linked recessive gene
Occurs more often in males than females
Often skips generations through female carriers (heterozygotes). All of the daughters of affected males are carriers.

117. 3. Always fill in the genotypes for individuals in the pedigree.

118. 3. Always fill in the genotypes for individuals in the pedigree.
Doing this will help you double check that you determined the correct pattern of inheritance.

119. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Autosomal Recessive
Sex-Linked Recessive

120. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Autosomal Recessive
Sex-Linked Recessive

121. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Equally likely to affect male and female
Autosomal Recessive
Sex-Linked Recessive

122. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Equally likely to affect male and female
Autosomal Recessive
May skip a generation; may have multiple affected in a single generation (horizontal pattern)
Sex-Linked Recessive

123. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Equally likely to affect male and female
Autosomal Recessive
May skip a generation; may have multiple affected in a single generation (horizontal pattern)
Sex-Linked Recessive

124. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Equally likely to affect male and female
Autosomal Recessive
May skip a generation; may have multiple affected in a single generation (horizontal pattern)
Sex-Linked Recessive
May skip a generation; all daughters of affected males are carriers

125. Patterns in Pedigrees Inheritance Affected Generations
Affected Males and Females
Autosomal Dominant
Trait appears in every generation (vertical pattern)
Equally likely to affect male and female
Autosomal Recessive
May skip a generation; may have multiple affected in a single generation (horizontal pattern)
Sex-Linked Recessive
May skip a generation; all daughters of affected males are carriers
More often male than female