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3. Gregor Mendel (1822-1884) Responsible for discovering the laws governing inheritance of traits

4.  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century (1900’s)

5.  Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants  He found that the plants' offspring retained traits of the parents  He is called the “Father of Genetics"

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7.  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually chromosomes & DNA

8. Chromosome Terminology Homologous chromosomes: a matching pair of chromosomes that are inherited one from each parent Sister chromatids are identical

9. Chromosome Terminology

10.  Trait - any characteristic that can be passed from parent to offspring  Heredity - passing of traits from parent to offspring  Genetics - study of heredity

11.  Monohybrid cross - cross involving a single trait e.g. flower color  Dihybrid cross - cross involving two traits e.g. flower color & plant height

12. Used to help solve genetics problems

13. 0 100% 0% Homozygous Dominant Parent Homozygous Recessive Parent 4 Heterozygous Offspring

14.  Alleles – possible forms of a gene (dominant & recessive)  Dominant - stronger of two genes expressed in the hybrid; will mask a recessive trait; represented by a capital letter (R)  Recessive - gene that shows up less often in a cross; hidden by a dominant trait; represented by a lowercase letter (r)

15.  Genotype - gene combination for a trait (example: RR, Rr, rr)  Phenotype - the physical feature resulting from a genotype (example: red, white) (example: red, white)

16. Genotype of alleles: R = red flower r = yellow flower All genes occur in pairs, so 2 alleles affect a characteristic Possible combinations are: GenotypesRR Rrrr PhenotypesRED RED YELLOW

17.  Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (example: RR or rr); also called pure  Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (example: RR or rr); also called pure  Heterozygous genotype - gene combination of one dominant & one recessive allele (example: Rr); also called hybrid

21.  Can be grown in a small area  Produce lots of offspring  Produce pure plants when allowed to self- pollinate for several generations  Can be artificially cross-pollinated

22. Mendel hand-pollinated flowers using a paintbrush Mendel hand-pollinated flowers using a paintbrush He could snip the stamens to prevent self- pollination He could snip the stamens to prevent self- pollination Covered each flower with a cloth bag Covered each flower with a cloth bag He traced traits through several generations He traced traits through several generations

23. How Mendel Began Mendel produced pure strains by allowing the plants to self- pollinate for several generations

24. Flower color --- Purple (P) or white ( p ) Flower color --- Purple (P) or white ( p ) Flower position---Axial (A) or Terminal (a) Flower position---Axial (A) or Terminal (a) Seed color ---- Yellow (Y) or Green ( y ) Seed color ---- Yellow (Y) or Green ( y ) Seed shape --- Round (R) or Wrinkled (r) Seed shape --- Round (R) or Wrinkled (r) Pod shape --- Smooth (S) or wrinkled ( s ) Pod shape --- Smooth (S) or wrinkled ( s ) Pod color --- Green (G) or Yellow (g) Pod color --- Green (G) or Yellow (g) Stem length --- Tall (T) or Short (t) Stem length --- Tall (T) or Short (t)

25. Parental P 1 Generation = the parental generation in a breeding experiment Parental P 1 Generation = the parental generation in a breeding experiment F 1 generation = the first-generation offspring in a breeding experiment F 1 generation = the first-generation offspring in a breeding experiment From breeding individuals from the P 1 generation with each other From breeding individuals from the P 1 generation with each other F 2 generation = the second-generation offspring in a breeding experiment F 2 generation = the second-generation offspring in a breeding experiment From breeding individuals from the F 1 generation with each other From breeding individuals from the F 1 generation with each other

26. How Mendel Proceeded Mendel crossed his parental generation (P) of a homozygous dominant trait (XX) with his parental generation (P) of a homozygous recessive trait (xx). (He did not know about dominant and recessive traits, so he was lucky that the traits he chose were ones that were controlled by one gene!) The first generation (F 1 ) offspring all appeared with the dominant trait showing as a phenotype. All their genotypes were heterozygous (Xx). 0

27. How Mendel Continued Mendel then crossed his first generation heterozygous offspring (F 1 ) with more of his first generation heterozygous offspring (F 1 ). The second generation (F 2 ) had recessive traits show up again at a genotype ratio of 1:2:1, meaning 1 AA, 2 Aa and 1 aa. Heterozygous Offspring Ratios of 1:2:1 meaning 1AA:2Aa:1aa

28. P = Cross 2 Pure Plants AA x aa F 1 = Results in 4 Yellow Hybrids Aa F 2 = Cross 2 Hybrids for 3 Yellow and 1 Green 1 AA, 2 Aa, 1 aa

29. Mendel’s Experimental Results

30. Did the observed ratio match the theoretical ratio? The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round:1 wrinkled Mendel’s observed ratio was 2.96:1 The discrepancy is due to statistical error The larger the sample the more nearly the results approximate to the theoretical ratio

32.  Homozygous dominant x Homozygous recessive  Offspring all Heterozygous (hybrids)  Offspring called F 1 generation  Genotypic & Phenotypic ratio is ALL ALIKE

33. Trait: Seed Shape Trait: Seed Shape Alleles: R – Roundr – Wrinkled Alleles: R – Roundr – Wrinkled Cross: Round seeds x Wrinkled seeds Cross: Round seeds x Wrinkled seeds RR x rr RR x rr R R rr Rr Genotype:Rr Genotype: Rr PhenotypeRound Phenotype: Round Genotypic Ratio:All alike Genotypic Ratio: All alike Phenotypic Ratio: All alike

34.  Heterozygous x heterozygous  Offspring: 25% Homozygous dominant RR 50% Heterozygous Rr 25% Homozygous Recessive rr  Offspring called F 2 generation  Genotypic ratio is 1:2:1  Phenotypic Ratio is 3:1

35. Trait: Seed Shape Trait: Seed Shape Alleles: R – Roundr – Wrinkled Alleles: R – Roundr – Wrinkled Cross: Round seeds x Round seeds Cross: Round seeds x Round seeds Rr x Rr R r rR RR rrRr Genotype:RR, Rr, rr Genotype: RR, Rr, rr PhenotypeRound & wrinkled Phenotype: Round & wrinkled Genotype Ratio:1:2:1 Genotype Ratio: 1:2:1 Phenotype Ratio: 3:1

37. Mendel then crossed a pure & a hybrid from his F 2 generation Mendel then crossed a pure & a hybrid from his F 2 generation This is known as an F 2 or test cross This is known as an F 2 or test cross There are two possible testcrosses: Homozygous dominant x Hybrid Homozygous recessive x Hybrid There are two possible testcrosses: Homozygous dominant x Hybrid Homozygous recessive x Hybrid

38.  Homozygous x heterozygous(hybrid)  Offspring: 50% Homozygous RR or rr 50% Heterozygous Rr  Phenotypic Ratio is 1:1  Called Test Cross because the offspring have SAME genotype as parents

39. Trait: Seed Shape Trait: Seed Shape Alleles: R – Roundr – Wrinkled Alleles: R – Roundr – Wrinkled Cross: Round seeds x Round seeds Cross: Round seeds x Round seeds RR x Rr R R rR RR RrRR Rr Genotype:RR, Rr Genotype: RR, Rr PhenotypeRound Phenotype: Round Genotypic Ratio:1:1 Genotypic Ratio: 1:1 Phenotypic Ratio: All alike

40. Trait: Seed Shape Trait: Seed Shape Alleles: R – Roundr – Wrinkled Alleles: R – Roundr – Wrinkled Cross: Wrinkled seeds x Round seeds Cross: Wrinkled seeds x Round seeds rr x Rr rr x Rr r r rR Rr rrRr rr Genotype:Rr, rr Genotype: Rr, rr PhenotypeRound & Wrinkled Phenotype: Round & Wrinkled Genotype Ratio:1:1 Genotype Ratio: 1:1 Phenotype Ratio: 1:1

42. In a cross of parents that are pure for contrasting traits (AA and aa), only one form of the trait will appear in the next generation. All the offspring will be heterozygous and express only the dominant trait. RR x rr yields all Rr (round seeds)

44. During the formation of gametes (eggs or sperm), the pair of alleles responsible for a trait separate from each other, so each gamete only receives one copy of a gene. During the formation of gametes (eggs or sperm), the pair of alleles responsible for a trait separate from each other, so each gamete only receives one copy of a gene. These alleles are then randomly united at fertilization, producing the genotype for the traits of the offspring. These alleles are then randomly united at fertilization, producing the genotype for the traits of the offspring.

46. Alleles for different traits are distributed to sex cells (& offspring) independently of one another. Alleles for different traits are distributed to sex cells (& offspring) independently of one another. This law can be illustrated using dihybrid crosses. This law can be illustrated using dihybrid crosses.

48. A breeding experiment that tracks the inheritance of two traits. A breeding experiment that tracks the inheritance of two traits. Mendel’s Law of Independent Assortment Mendel’s Law of Independent Assortment Each pair of alleles segregates independently during gamete formation Each pair of alleles segregates independently during gamete formation Formula: 2 n (n = # of heterozygotes) for all gamete possibilities Formula: 2 n (n = # of heterozygotes) for all gamete possibilities

49. Remember: 2 n (n = # of heterozygotes) Remember: 2 n (n = # of heterozygotes) 1.RrYy 1.RrYy 2.AaBbCCDd 2.AaBbCCDd 3.MmNnOoPPQQRrssTtQq 3.MmNnOoPPQQRrssTtQq

50. 1. Rr Yy: 2 n = 2 2 = 4 gametes RY Ry rY ry 2. Aa Bb CC Dd: 2 n = 2 3 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3.Mm Nn Oo PP QQ Rr ss Tt Qq: 2 n = 2 6 = 64 gamete possibilities 2 n = 2 6 = 64 gamete possibilities

51. Traits: Seed shape & Seed color Traits: Seed shape & Seed color Alleles: Alleles: R round Y yellow r wrinkled y green RrYy x RrYy RY Ry rY ry All possible gamete combinations

52. RYRyrYry RYRy rY ry

53. RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy 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 RYRyrYry RY Ry rY ry

54. Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1

55. A mating between an individual of unknown genotype and a homozygous recessive individual. A mating between an individual of unknown genotype and a homozygous recessive individual. Example: bbC__ x bbcc Example: bbC__ x bbcc BB = brown eyes BB = brown eyes Bb = brown eyes Bb = brown eyes bb = blue eyes bb = blue eyes CC = curly hair CC = curly hair Cc = curly hair Cc = curly hair cc = straight hair cc = straight hairbCb___bc

56. Possible results: Possible results:bCb___bcbbCc CbCb___bc bbccor c

57. LAW PARENT CROSS OFFSPRING DOMINANCE (dominant trait masks a recessive trait) TT x tt tall x short 100% Tt tall SEGREGATION (traits separate from each other when sorted) Tt x Tt tall x tall 75% tall 25% short INDEPENDENT ASSORTMENT (different traits sort separately from each other) RrGg x RrGg round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods

59. F 1 hybrids in betweenphenotypes F 1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Example:snapdragons (flower) Example: snapdragons (flower) red (RR) x white (rr) RR = red flower rr = white flower R R

60. RrRrRrRr R R All Rr = pink (heterozygous pink) produces the F 1 generation R R r r R r R r 1:2:1 produces the F 2 generation

62. Both alleles are expressed (multiple alleles) in heterozygous individuals. Both alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type Example: blood type 1.type A= I A I A or I A i 2.type B= I B I B or I B i 3.type AB= I A I B 4.type O= ii

63. Example: homozygous male Type B (I B I B ) x heterozygous female Type A (I A i) IAIBIAIB IBiIBi IAIBIAIB IBiIBi 1/2 = I A I B 1/2 = I B i IBIB IAIA i IBIB

64. Example:Example: male Type O (ii) x female type AB (I A I B ) IAiIAiIBiIBi IAiIAiIBiIBi 1/2 = I A i 1/2 = I B i i IAIA IBIB i

65. Question : If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? Question : If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? boy - type O (ii) X girl - type AB (I A I B ) boy - type O (ii) X girl - type AB (I A I B )

66. Answer: Answer: IAIBIAIB ii Parents: genotypes genotypes = I A i and I B i phenotypes phenotypes = A and B IBIB IAIA i i

67. Traits (genes) located on the sex chromosomes Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y Sex chromosomes are X and Y XX genotype for females XX genotype for females XY genotype for males XY genotype for males Many sex-linked traits carried on X chromosome Many sex-linked traits carried on X chromosome Males will show recessive traits on their X chromosome without a matching gene on the Y chromosome to mask it (ex: color blindness) Males will show recessive traits on their X chromosome without a matching gene on the Y chromosome to mask it (ex: color blindness)

68. Sex Chromosomes XX chromosome - femaleXy chromosome - male fruit fly eye color Example: Eye color in fruit flies

69. (red-eyed male) x (white-eyed female) X R Y x X r X r Remember: the Y chromosome in males does not carry traits. RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female XRXR XrXr XrXr Y

70. X R X r X r Y X R X r X r Y 50% red eyed female 50% white eyed male XRXR XrXr XrXr Y RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female

73. tall (TT) x dwarf (tt) pea plants tall (TT) x dwarf (tt) pea plants T T tt

74. T T tt Tt All Tt = tall (heterozygous tall) produces the F 1 generation tall (TT) vs. dwarf (tt) pea plants

75. tall (Tt) vs. tall (Tt) pea plants tall (Tt) vs. tall (Tt) pea plants T t Tt

76. TT Tt tt T t Tt produces the F 2 generation 1/4 (25%) = TT 1/2 (50%) = Tt 1/4 (25%) = tt 1:2:1 genotype 3:1 phenotype 3:1 phenotype tall (Tt) x tall (Tt) pea plants