1. Learning Objectives I will be able to:
Describe the work of Gregor Mendel
Distinguish between dominant and recessive traits
Describe the law of segregation and law of independent assortment

2. Learning Objectives I will be able to:
Distinguish between genotype and phenotype
Identify homozygous and heterozygous alleles
Use a Punnett square to predict the results of monohybrid and dihybrid crosses
Explain how a testcross shows the genotype of an individual whose phenotype expresses the dominant trait

3. Gregor Mendel (1822-1884) Considered the “father of genetics”
Studied traits in pea plants

4. Gregor Mendel ( )
Character – heritable feature; like flower color

5. Gregor Mendel ( )
Traits – variant of a character; like purple/white flowers

6. Gregor Mendel ( )

7. Gregor Mendel ( )
P generation – parent generation

8. Gregor Mendel ( )
F1 generation – offspring of the P generation

9. Gregor Mendel (1822-1884) F2 generation – offspring of F1 generation
Gene – region of DNA that codes for a particular protein

10. Alleles Alleles – various forms of a gene (letters)
Typically a dominant allele and a recessive allele

11. Alleles Dominant allele masks the recessive allele
Dominant brown (B) masks recessive blue (b)

12. Genotype vs. Phenotype Genotype - Alleles present in an organism
BB, Bb, bb
Phenotype – physical characteristic
brown eyes or blue eyes

13. Heterozygous vs. Homozygous
Heterozygous – 2 different alleles Bb
Homozygous – two of the same allele
BB – brown eyes
bb – blue eyes

14. Law of Segregation
During meiosis, the hereditary factor (homologous pair of chromosomes) separate
Offspring receives one allele from each parent

15. Law of Segregation
During meiosis, the hereditary factor (homologous pair of chromosomes) separate
Offspring receives one copy from each parent

16. Law of Independent Assortment
Factors of different traits will be distributed independent of each other

17. Monohybrid Crosses
Cross with only one gene
Uses Punnett square

18. Homozygous Dominant x Homozygous Recessive
Graphic organizer #1

19. Homozygous Dominant x Homozygous Recessive
Genotype: 4Bb
Phenotype: 4 brown eyes

20. Homozygous Dominant x Homozygous Recessive
G: 4Bb
P: 4 brown eyes

21. Homozygous Dominant x Homozygous Recessive
Organizer #2
W = tall
w = short
Genotype:
Phenotype:

22. You find a yellow pea plant. You know that yellow is dominant to green
You find a yellow pea plant. You know that yellow is dominant to green. What is the genotype?

23. Test Cross Tests what alleles are present
Cross a dominant phenotype with a recessive phenotype

24. Test Cross Tests what alleles are present
Cross a dominant phenotype with a recessive phenotype

25. Test Cross

26. Dihybrid Crosses Cross between 2 different genes Color and seed skin
16 squares

27. Dihybrid Crosses Cross between 2 different genes Color and seed skin
16 squares

28. Heterozygous x Heterozygous
#1 in notes
RrYy x RrYy

29. Dihybrid Cross RrYy x RrYy R = round r = wrinkled Y = yellow y = green
RY Ry rY ry
RY Ry rY ry

30. Dihybrid Cross Round/Yellow: Round/green: wrinkled/Yellow:
wrinkled/green:
Phenotypic ratio: RY Ry rY ry RY Ry rY ry

31. Dihybrid Cross RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy
Round/Yellow: 9
Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic ratio

32. Dihybrid Cross #2 in notes Parent A: heterozygous for both traits
Parent B:
Heterozygous for height
Homozygous recessive for eye color
If height is represented by H and eye color is represented by B, what will the cross look like?

33. Dihybrid Cross Organizer #9 HhBb x Hhbb H = tall h = short
B = brown eyes
b = blue eyes

34. Dihybrid Cross
HhBb x Hhbb
HB, Hb, hB, hb
Hb, Hb, hb, hb

35. Dihybrid Cross
HB Hb hB hb Hb Hb hb hb

36. Dihybrid Cross HB Hb hB hb Hb Hb hb hb HHBb HHbb HhBb Hhbb

37. Dihybrid Cross Phenotype? Tall/brown eyes: Tall/blue eyes:
Short/brown eyes:
Short/blue eyes:

38. Dihybrid Cross Phenotype? Tall/brown eyes: 6 Tall/blue eyes: 6
Short/brown eyes: 2
Short/blue eyes: 2

39. Incomplete Dominance
Dominant trait is not completely expressed over recessive trait
Heterozygous forms “hybrid”
snapdragons

40. Incomplete Dominance

41. Pink flowers (Rr) x pink flowers (Rr)

42. Incomplete Dominance Genotype: 1RR:2Rr:1rr Phenotype:
1 red:2 pink:1 white

43. Pink flowers x pink flowers
Genotype:
1RR:2Rr:1rr
Phenotype:
1 red:2 pink:1 white

44. Pink flowers x Red flowers
R R R r

45. Pink flowers x red flowers
R R
G: 2RR:2Rr
P: 2red:2pink:
R RR RR
r Rr Rr

46. Codominance 2 alleles are expressed at the same time
2 alleles are dominant

47. Codominance
B B
Black x white chicken W

48. Codominance B B Black x white chicken G: 4BW P: 4 speckled W BW BW

49. Codominance
Now cross 2 speckled chickens
BW x BW

50. Codominance B W G: 1BB:2BW:1WW B BB BW P: 1 black, 2 speckled, 1 white
W BW WW
G: 1BB:2BW:1WW
P: 1 black, 2 speckled, 1 white

51. Multiple Alleles More than 2 alleles code for a trait Blood types
Which blood types do you know?

52. Multiple Alleles More than 2 alleles code for a trait Blood types
Which blood types do you know?
A, B, AB, and O are the standard types

53. Multiple Alleles
A and B are dominant
O is recessive

54. Multiple Alleles Mother has AB blood (IAIB) Father has B blood (IBi)
IAIB x IBi

55. Multiple Alleles
Phenotypes:
1 AB blood
1 A blood
2 B blood

56. Multiple Alleles Mother has IBIB blood Father has IAi blood
Draw the Punnett square

57. Multiple Alleles
IB IB
IA IA IB IA IB
i IB i IB i
Phenotype:
2 AB
2 B

58. Sex Linked Traits Traits located on X or Y chromosome
Much more common in males than females
Why?

59. Sex Linked Traits Traits located on X or Y chromosome
Much more common in males than females

60. Y linked Traits Relatively uncommon
SRY gene – provides “male information”

61. X linked Traits Much more common Disorders like hemophilia
Blood clotting disorder
Common in old European royalty
red-green colorblindness
Much more common in males than females

62. Sex linked Punnett square
The first step in making a sex linked Punnett square is always to write down the Xs and Ys of mom and dad!

63. X linked Traits Example Normal father x carrier mother
Then do this as you would do a normal Punnett square

64. X linked Traits Phenotype 2 normal females 1 normal male
1 colorblind male
Genotype
1XBXB female
1XBXb female
1XBY male
1XbY male

65. X linked Traits Try your luck! Mother who is carrier for hemophilia
XHXh
Normal father
XHY

66. X linked Traits
XH Xh
XH XH XH
Y XHY XhY

67. Sex Influenced Traits Found on autosomes, not sex chromosomes
Influenced by sex
Often affected by hormones
baldness

68. Sex Influenced Traits Female Male HH Normal Normal Hh Normal Disease
hh Disease Disease

69. Pedigree
Family tree used to show traits inherited over time

70. Pedigree If trait is autosomal, it will appear in both sexes equally
If sex-linked, it will appear in males much more often

71. Recessive Pedigree
This pedigree codes for brown eyes (B) and blue eyes (b)
Pedigree graphic organizer

72. Dominant Pedigree
Aa Aa aa Aa
A? A? aa aa Aa
aa aa aa

73. Hemophilia Pedigree

74. Polygenic Traits Trait that is coded for by more than one gene
Usually continuous traits in humans
Height
Skin color

75. Linkage Groups
Linkage groups – genes that tend to be inherited together
Genes located close together on one chromosome
Avoid crossing-over.

76. Alterations in Chromosome Structure
Deletion – pieces of a chromosome are removed

77. Alterations in Chromosome Structure
Duplication – pieces of a chromosome are duplicated

78. Alterations in Chromosomes
Inversion – pieces of a chromosome are inverted

79. Alteration in Chromosomes
Translocation – part of a chromosome attaches to a non-homologous chromosome