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1 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dominant Recessive F2 Generation 1. Flower Color Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 705 Purple: 224 White X 3.15:1 Purple White 2. Seed Color 6022 Yellow: 2001 Green X Petals Carpel (female) Yellow Green Stigma Style 3.01:1 3. Seed Texture Anthers (male) 1. The anthers are cut away on the purple flower. 2. Pollen is obtained from the white flower. 3. Pollen is transferred to the purple flower. 4. All progeny result in purple lowers. 5474 Round: 1850 Wrinkled X 2.96:1 Round Wrinkled 4. Pod Color 428 Green: 152 Yellow X 2.82:1 Green Yellow 5. Pod Shape 882 Inflated: 299 Constricted X 2.95:1 Inflated Constricted 6. Flower Position 651 Axial: 207 Terminal X Axial Terminal 3.14:1 7. Plant Height © Leslie Holzer/Photo Researchers, Inc. 787 T all: 277 Short X 2.84:1 3 Tall Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Truebreeding Purple Parent 4 Short Truebreeding White Parent P Parent generation p P p pp P p P Pp p pp White parent pp Cross-fertilize 1. p + p = pp. Purple Offspring P P 2. P + p = Pp. P p Pp p P PP Pp Self-cross Purple Dominant Purple Dominant Purple Dominant p White Recessive pP 3. p + P = pP. pp p pP pp Pp Pp Pp Pp P F1 generation P p p Purple parent PP F1 generation Purple heterozygote Pp 4. P + P = PP. a. F2 generation (3:1 phenotypic ratio) p P Truebreeding Non-truebreeding Non-truebreeding Truebreeding Self-cross Self-cross Self-cross Self-cross Purple heterozygote Pp P PP Pp pP pp p F3 generation (1:2:1 genotypic ratio) F2 generation 3 Purple:1 White (1PP: 2Pp :1pp ) 5 b. 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dominant Pedigree Generation I 1 2 2 3 Generation II 1 4 5 2 3 Generation III 1 Key unaffected male affected male unaffected female affected female 7 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Recessive Pedigree RR YY One of these persons is heterozygous Generation I 1 rr yy Parent generation Meiosis Meiosis 2 Cross-Fertilization Heterozygous Rr Yy Generation II 1 2 3 4 5 F1 generation Meiosis (chromosomes assort independently into four types of gametes) Generation III 1 2 3 4 5 6 7 RY Mating between first cousins Generation IV Ry rY ry F1 X F1 (RrYy X RrYy) 1 2 3 Homozygous recessive RY RY Key F2 generation Ry rY unaffected male affected male male carrier unaffected female affected female female carrier ry 9 RR YY RR Yy Rr YY Rr Yy Ry RR Yy rY Rr YY ry Rr Yy RR yy Rr Yy Rr Yy rr YY Rr yy rr Yy Rr yy rr Yy 9/16 round, yellow 3/16 round, green 3/16 wrinkled, yellow 1/16 wrinkled, green rr yy 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dominant Phenotype (unknown genotype) Homozygous recessive p Homozygous dominant Homozygous recessive p p Heterozygous dominant P Pp Pp P Pp Pp Alternative 1: All offspring are purple and the unknown flower is homozygous dominant P PP or Pp? If PP If Pp then then p Pp Pp pp pp p Alternative 2: Half of the offspring are white and the unknown flower is heterozygous dominant 11 12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SCIENTIFIC THINKING Hypothesis: The pink F1 observed in a cross of red and white Japanese four o’clock flowers is due to failure of dominance and is not an example of blending inheritance. Prediction: If pink F1 are self-crossed, they will yield progeny thesame as the Mendelian monohybrid genotypic ratio. This would be1 red: 2 pink: 1 white. Test: Perform the cross and count progeny. C RC R CWCW Parent generation Cross-fertilization C RC W F1 generation F2 generation CR CW C RC R C RC W C RC W CWCW CR CW 1:2:1 CRCR: CRCW: CWCW Result: When this cross is performed, the expected outcome is observed. Conclusion: Flower color in Japanese four o’clock plants exhibits incomplete dominance. 13 Further Experiments: How many offspring would you need to count to be confident in the observed ratio? 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sugars Exhibited Blood Type Alleles IAIA, IAi (IA dominant to i) IBIB, IBi (IB dominant to i) IAIB (codominant) A Galactosamine Receives A and O Donates to A and AB B Galactose Receives B and O Donates to B and AB Both galactose and galactosamine Universal receiver Donates to AB None Receives O Universal donor AB ii (i is recessive) O temperature below 33°C, tyrosinase active, dark pigment Donates and Receives Temperature above 33°C, tyrosinase inactive, no pigment 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. White (AAbb) Parental generation Cross-fertilization White (aaBB) All Purple (AaBb) F1 generation AB Ab aB ab AABB AABb AaBB AaBb AABb AAbb AaBb Aabb AaBB AaBb aaBB aaBb Aabb aaBb aabb AB Ab F2 generation aB ab AaBb 9/16 Purple: 7/16 White a. Precursor (colorless) b. Enzyme A Intermediate (colorless) Enzyme B Pigment (purple) 17 © DK Limited/Corbis. 16
