1. 1 Chapter 8- Mendel And Heredity

2. 2 I. The origins of Genetics A. The passing of traits from parents to offspring is called heredity. 1. Mendel was a mathematician and looked at genetics differently than anyone in the past ever did.

3. 3 2. Genetics is the branch of biology that focuses on heredity. 3. Mendel counted the number of each kind of offspring and analyzed the data. 4. Quantitative approaches to science-those that include measuring and counting.

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5. 5 B. Useful features in peas 1. The garden pea is a good subject for studying heredity for several reasons.

6. 6 a. The garden pea has many traits that have two clearly different forms that are easy to tell apart. b. The mating of the garden pea flowers can be easily controlled. c. The garden pea is small, grows easily, matures quickly and produces many offspring.

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8. 8 C. Mendel observed that traits are expressed as simple ratios 1. Mendel ’ s initial experiments were monohybrid crosses. A cross with ONE pair of contrasting traits. 2. Mendel allowed true breeding or self- pollination to occur.

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10. 10 3. These true-breeding plants served as the parental generation in Mendel ’ s experiments. 4. The parental generation, or P generation are the first two individuals that are crossed.

11. 11 5. Mendel crossed the P generation to get the F1 generation. First generation. He then examined each F1 plant and recorded the number of F1 plants and their traits. 6. Mendel then mated the F1 generation to get a F2 generation. The second generation and then again examined each of their traits.

12. 12 D. Mendel’s results P generation (true-breeding parents) Purple flowersWhite flowers F 1 generation All plants have purple flowers F 2 generation Fertilization among F 1 plants (F 1  F 1 ) of plants have purple flowers 3–43–4 of plants have white flowers 1–41–4 Mendel’s Results

13. 13 II. Mendel’s theory A. Mendel ’ s work became a theory of heredity. 1. The four hypotheses Mendel developed were based directly on the result of his experiments.

14. 14 a. For each inherited trait, an individual has two copies of genes- one from each parent. b. There are alternative versions of genes. These are called alleles.

15. 15 c. When two different alleles occur together, one of them bay be completely expressed, while the other may have no affect on the appearance. Mendel explained these to be dominant and recessive. d. When gametes are formed, the alleles for each gene in an individual separate independently of one another.

16. 16 B. Mendel ’ s findings in modern terms 1. If two traits are the same they are called homozygous. 2. If two traits are different they are called heterozygous.

17. 17 3. Dominant genes are expressed with capital letters. 4. Recessive genes are expressed with lower caps. 5. Example Brown is dominant= B, blue is recessive =b. 6. A set of alleles that an individual has is called the genotype.

18. 18 7. What the individual expresses is called the phenotype. 8. Example: BB, Bb and bb are genotypes. 9. BB, and Bb would have brown eyes, and bb would have blue eyes. The colors are the phenotypes.

19. 19 Freckles Widow’s peak Free earlobe No freckles Straight hairline Attached earlobe Dominant Traits Recessive Traits

20. Phenotype Dihybrid Cross

21. Mendel also performed crosses involving two pairs of traits, e.g., seed shape (smooth vs. wrinkled) and color (yellow vs. green). Mendel’s dihybrid crosses:

22. Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall Pea Traits:

23. Dihybrid Cross Example:

24. Dihybrid crosses: SsYy

25. Dihybrid Crosses:

26. 26 B. Mendel ’ s Ideas gave rise to the laws of heredity. 1. The first law, the law of segregation, states that the two alleles for a trait segregate or separate when gametes are formed.

27. P plants 1–21–2 1–21–2 Genotypic ratio 1 PP : 2 Pp : 1 pp Phenotypic ratio 3 purple : 1 white F 1 plants (hybrids) Gametes Genetic makeup (alleles) All All Pp Sperm Eggs PP p ppPp P p P p P P p PP pp All Gametes F 2 plants The Law of Segregation

28. 28 2. The law of independent assortment states that the alleles of different genes separate independently of one another during gamete formation.

29. P generation 1–21–2 Hypothesis: Dependent assortment Hypothesis: Independent assortment 1–21–2 1–21–2 1–21–2 1–41–4 1–41–4 1–41–4 1–41–4 1–41–4 1–41–4 1–41–4 1–41–4 9 –– 16 3 –– 16 3 –– 16 1 –– 16 RRYY Gametes Eggs F 1 generation Sperm F 2 generation Eggs Gametes rryy RrYy ry RY ry RY ry RY Hypothesized (not actually seen) Actual results (support hypothesis) RRYY rryy RrYy ry RY RRYY rryy RrYy ry RY RrYy rrYYRrYY RRYyRrYY RRYy rrYy Rryy RRyy rY Ry ry Yellow round Green round Green wrinkled Yellow wrinkled RY rY Ry The law of independent assortment

30. 30 II. Studying heredity A. Punnet squares

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32. F 1 genotypes 1–21–2 1–21–2 1–21–2 1–21–2 1–41–4 1–41–4 1–41–4 1–41–4 Formation of eggs Bb female F 2 genotypes Formation of sperm Bb male B B B B B B b b b bb b B. Probability

33. 33 C. Pedigrees

34. Symbols Pedigree Sample

35. Rather than manipulate mating patterns of people, geneticists analyze the results of matings that have already occurred. In a pedigree analysis, information about the presence/absence of a particular phenotypic trait is collected from as many individuals in a family as possible and across generations. The distribution of these characters is then mapped on the family tree. Pedigree analysis

36. For example, the occurrence of widows peak (W) is dominant to a straight hairline (w). The relationship among alleles can be integrated with the phenotypic appearance of these traits to predict the genotypes of members of this family. Pedigree analysis

37. Examples: Widow’s Peak & Earlobes

38. Is widow’s peak a dominant or recessive trait? Widow’s Peak No Widow’s Peak

39. Is an attached earlobe a dominant or recessive trait? Attached Earlobe Free Earlobe

40. D. Sex-Linked Traits

41. Sex-Linked Traits

42. 42 Color-Blindness

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46. What type of inheritance pattern? Color blindnessRed-Green

47. Queen Victoria Albert Alice Louis Alexandra Czar Nicholas II of Russia Alexis Hemophilia in the royal family of Russia

48. XNXN Y XNXN XnXn XNXNXNXN XNYXNY XNXnXNXn XnYXnY Hemophilia Example N = Normal Bloodn = Hemophilia

49. 49 III. Patterns of Heredity can be complex A. Traits influenced by several genes 1. When several genes influence a trait, the trait is said to be polygenetic.

50. Polygenic Inheritance Example Polygenic (multiple Genes) for a given phenotypic character. Example: Skin Color, Eye Color, Hair Color, & Rh Factor.

51. Polygenic Inheritance Example: Skin Color The melanin factor is located on three loci of each chromosome. (total of six locations)

52. Polygenic Inheritance: Human skin color is a good example of polygenic (multiple gene) inheritance. AABBCC Most Melanin aabbcc Least Melanin Assume that three "dominant" capital letter genes (A, B and C) control dark pigmentation because more melanin is produced. The "recessive"alleles of these three genes (a, b & c) control light pigmentation because lower amounts of melanin are produced.

53. Polygenic Inheritance Example Let’s do a cross. ABC A B C abc a b c X

54. 54 Polygenic Inheritance Example Result would be the F1 generation would be AaBbCc. abc ABC abc ABC abc ABC F1

55. Polygenic Inheritance Example Let’s cross the F1 with another F1. ABC a b c X ABC a b c

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57. Polygenic Inheritance Example F2 F1 F2

58. Gametes ABC ABc AbC Abc aBC aBc abC abc ABC65545443 ABc54434332 AbC54434332 Abc43323221 aBC54434332 aBc43323221 abC43323221 abc32212110 Polygenic Inheritance Example: Skin Color ABC/ ABC ABC/ ABc ABc/ ABc

59. 59 2. In some traits there is neither dominant nor recessive genes. These are called incomplete dominance. Example: Red flower RR and a White WW flower both with incomplete dominance will have pink flowers.

60. Incomplete Dominance Example X = Red Carnation White Carnation X = Pink Carnation

61. Incomplete Dominance with Snapdragons Flower Color P Generation F 1 Generation F 2 Generation Red C R Gametes CRCR CWCW  White C W Pink C R C W Sperm CRCR CRCR CRCR CwCw CRCR CRCR Gametes 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 Eggs 1⁄21⁄2 C R C R C W C W C R C W

62. 62 3. When two dominant alleles are expressed at the same time, both forms of the trait are displayed this is called co dominance. Example: Coat colors in a horse. 4. Genes with three or more alleles are said to have multiple alleles. Example blood groups ABO.

63. BW BW BW BW checkered chicken WW X BB BB W W BW Example of Codominance: In chickens, black feather color (BB) is codominant to white feather color (WW). Both feather colors show up in a checkered pattern in the heterozygous individual (BW). Cross a checkered chicken with a checkered chicken.

64. Blood Types Multiple Alleles

65. 65 1. GenotypesPhenotypes AAA AoA BBB BoBAB ooO Multiple Alleles

66. B A

67. See page 261 Mendelian Inheritance In Humans

68. See page 261 Mendelian Inheritance In Humans

69. 69 5. An individual ’ s phenotype often depends on conditions in the environment. 6. Some traits are affected by the temperature, sunlight or seasons. 7. In humans the environment influences height. Height is influenced by nutrition, an internal environment conditions.

70. Full coat color: CC CC ch Cc h Cc Chinchilla coat color: c ch c ch c h c ch c Himalayan coat color: c h c h c **temp Sensitive! Albino coat color: cc Multiple Alleles

71. 71 B. Some traits are caused by mutations

72. Sickle Cell Anemia ** NN is Not afflicted; Nn is a carrier; nn is afflicted **Sickle cell anemia is caused by an abnormal type of hemoglobin and cells become sickle shaped when oxygen is low **Sickle cells clot give rise to recurrent painful episodes called a “sickle cell pain crisis” ** “n” makes a person immune to malaria

73. Results in the absence of an enzyme that normally breaks down a lipid (fat) produced and stored in nervous tissues and brain

74. A child with Tay-Sachs Syndrome are mentally challenged

75. Phenylketonuria (PKU)  lacks an enzyme that converts one amino acid, phenylalanine, to a different amino acid, tyrosine. * Results in severe damage to the central nervous system. When detected in infants, dietary adjustments (about 1 in 15k babies born with it)

76. Phenylketonurics: Contains Phenylalanine

77. Genetic Methemoglobinemia *Although oxygen-poor blood is NOT blue, but appears bluish because of the distortion of skin “Blue People” who have too much methhemoglobin in their blood and oxygen cannot bind due to an enzyme deficiency **The Fugates of Hazard, Kentucky. Mom was a carrier while Dad had the disease Picture taken in the 1950’s

79. It results in a breakdown of certain areas of the brain. ~ Causes dementia due to progressive deterioration of the brain, increase in involuntary movements, eventually bedridden

80. Achondroplasia - type of dwarfism. AA genotypes are lethal and result in spontaneous abortion, Aa have dwarfism. 99% of Americans are aa

81. Polydactyl (extra fingers and/or toes): PP or Pp = extra digits. 98% of all people in the world are homozygous recessive (pp).

82. Progeria (very premature aging): * Most die before age 13 Spontaneous mutation of one gene creates a dominant mutation that rapidly accelerates aging.

83. 83 5. There is genetic testing to detect any bad genes. 6. Gene technology may soon by replacing defected genes with copies of healthy ones this is called gene therapy.