1. Biology I - GENETICS
1-12 Novak

2. Gregor Mendel

6. MENDEL’S PRINCIPLES

7. I. ALLELES
Any organism has two units of heredity (genes) for each trait in every body cell

8. II. SEGREGATION
The two units (genes) for a trait are separated in the cell; one gene is found on a chromosome while the other is located in the same place on its partner (homologous) chromosome

10. III. DOMINANCE
A. When two genes of a trait are different in the cells of the organism, the gene that shows up is the dominant while the gene that remains hidden is the recessive
B. Combinations of the two genes (genotypes)
1. Homozygous (pure) dominant - both genes are dominant
2. Homozygous (pure) recessive - both genes are recessive
3. Heterozygous (hybrid) - one gene is dominant & the other is recessive

11. IV. RECOMBINATION - (INDEPENDENT ASSORTMENT)
In each new generation there is a complete new rearrangement of the units of heredity (genes)

13. Following the Generations
Cross 2 Pure Plants TT x tt
Results in all Hybrids Tt
Cross 2 Hybrids get 3 Tall & 1 Short TT, Tt, tt

14. Generation “Gap”
Parental P1 Generation = the parental generation in a breeding experiment.
F1 generation = the first-generation offspring in a breeding experiment. (1st filial generation)
From breeding individuals from the P1 generation
F2 generation = the second-generation offspring in a breeding experiment. (2nd filial generation)
From breeding individuals from the F1 generation

15. Mendel’s Experimental Results

16. Thomas Hunt Morgan

21. Incomplete Dominance (blending inheritance)

22. INCOMPLETE DOMINANCE
A condition in which both alleles for a characteristic are partially expressed

23. Incomplete Dominance
F1 hybrids have an appearance somewhat in between or a blend of the phenotypes of the two parental varieties.
Example: snapdragons (flower)
red (RR) x white (WW)
R = red flower
W = white flower R W

24. Incomplete Dominance R RW produces the F1 generation All RW = pink
(heterozygous pink)
produces the
F1 generation W RW W

25. Incomplete Dominance

26. CODOMINANCE
A condition in which both alleles for a characteristic are fully expressed

27. Codominant white and pink

28. Codominant white and pink

29. Homozygous Red

30. Hereford Red

31. Homozygous white

32. Roan hybrid

33. Roan hybrid

34. Codominant cross

35. DIHYBRID INHERITANCE

36. These are the genotypes of the two plants.
Pea Plants
Seed Color
Height
Tall = TT, Tt
Short = tt
Yellow = YY, Yy
Green = yy
Let’s cross a homozygous tall (TT), homozygous yellow seed (YY) plant with a short (tt), green seed (yy) plant.
TTYY x ttyy
These are the genotypes of the two plants.

37. Independent Assortment
Mendels’ principle of Independent Assortment states that genes for different traits can segregate independently during the formation of gametes (eggs & sperm in animals, eggs and pollen in plants).
First T
TTYY
with first Y T Y
Gamete 1 = sperm, egg, pollen . . .

38. Independent Assortment
Mendels’ principle of Independent Assortment states that genes for different traits can segregate independently during the formation of gametes (eggs & sperm in animals, eggs and pollen in plants).
First T
TTYY
with second Y TY T Y
Gamete 1
Gamete 2

39. Independent Assortment
Mendels’ principle of Independent Assortment states that genes for different traits can segregate independently during the formation of gametes (eggs & sperm in animals, eggs and pollen in plants).
Second T
TTYY
with first Y TY TY T Y
Gamete 1
Gamete 2
Gamete 3

40. Independent Assortment
Mendels’ principle of Independent Assortment states that genes for different traits can segregate independently during the formation of gametes (eggs & sperm in animals, eggs and pollen in plants).
Second T
TTYY
with second Y TY TY TY T Y
Gamete 1
Gamete 2
Gamete 3
Gamete 4

41. Dihybrid Punnett Square - F1
P1 = TTYY TY ty
Will be F1 Generation
P2 = ttyy

42. Dihybrid Punnett Square - F1TY ty
TTYy

43. Dihybrid Punnett Square - F1TY ty
TtYy
TTYY
TtYY

44. Dihybrid Punnett Square - F1TY ty
TtYy

45. Dihybrid Punnett Square - F1TY ty
TtYy
Genotype ratio:
TtYy - 16/16
Phenotype ratio:
Tall, Yellow - 16/16

46. Dihybrid Punnett Square – F2 We need to pair up the genes which can be given to each gamete (egg and pollen). Let’s cross two of the plants from the F1 generation
We need to pair up the genes TY ty
TtYy . x T Y T y t Y t y

47. Dihybrid Punnett Square F2TY Ty tY ty
Both the plants can give the same gene combinations to their gametes, so the pairs along the top and down the side are the same.

48. Dihybrid Punnett Square – F2
When you pair up the gametes from the two plants, always put like letters together and within the like letters, put the CAPITAL letter in front of the lowercase letter.

49. Dihybrid Punnett Square F2TY Ty tY ty
TTYY
TTYy
TtYY
TtYy
????
Your Turn!!

50. Dihybrid Punnett Square F2TY Ty tY ty
TTYY
TTYy
TtYY
TtYy
TTyy
Ttyy
ttYY
ttYy
ttyy
F2 generation

51. Dihybrid Punnett Square F2
Genotype and phenotype ratios? TY Ty tY ty
TTYY
TTYy
TtYY
TtYy
TTyy
Ttyy
ttYY
ttYy
ttyy

52. F2 Genotype Ratio TTYY - 1 TTYy - 2 TtYY - 2 TtYy - 4 TTyy - 1

53. F2 Phenotype Ratio TTYY - 1 TTYy - 2 TtYY - 2 TtYy - 4
Tall, Yellow - 9
Tall, Green - 3
Short, Yellow - 3
Short, Green - 1

54. Another Mendelian Dihybrid Problem

57. Dihybrid F2 Results

58. Dihybrid F2 Results

59. Sex-Linked Inheritance

61. Color Blindness

62. TYPES OF COLOR BLINDNESS
normal - trichromatic color vision protanopia red-green blindness (no red cones) deutanopia red-green blindness (no green cones) tritanopia blue-yellow blindness (no blue cones) typical achromatopsia (no cones; rod monochromat) protanomaly (anomalous red cones) deutanomaly (anomalous green cones) tritanomaly (anomalous blue cones) atypical achromatopsia (low cones; cone monochromat)

63. Red Green Color Blindness Male1.01% Female0.02%

67. Sex-linked Traits Traits (genes) located on the sex chromosomes
Sex chromosomes are X and Y
XX genotype for females
XY genotype for males
Many sex-linked traits carried on X chromosome

72. Hemophilia

73. Female Carriers

74. The effects of hemophilia

77. Human Blood
Coagulation
Cascade

80. The End