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Incomplete Dominance Codominance Multiple Alleles

Incomplete Dominance Codominance Multiple Alleles. PP = purple. Pp = purple. pp = white. Review: Dominant/Recessive. One allele is dominant over the other (capable of masking the recessive allele). PP. Pp. Pp. pp. Review Problem: Dominant/Recessive.

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Incomplete Dominance Codominance Multiple Alleles

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  1. Incomplete DominanceCodominanceMultiple Alleles

  2. PP = purple Pp = purple pp = white Review: Dominant/Recessive • One allele is dominant over the other (capable of masking the recessive allele)

  3. PP Pp Pp pp Review Problem: Dominant/Recessive • In pea plants, purple flowers (P) are dominant over white flowers (p) show the cross between two heterozygous plants. P p GENOTYPES: - PP (1); Pp (2); pp (1) - ratio 1:2:1 P p PHENOTYPES: - purple (3); white (1) - ratio 3:1

  4. RR = red rr = white Rr = pink Incomplete Dominance • A third (new) phenotype appears in the heterozygous condition. • Flower Color in 4 O’clocks

  5. R r r r Rr Rr rr rr Problem: Incomplete Dominance • Show the cross between a pink and a white flower. GENOTYPES: - Rr (2); rr (2) - ratio 1:1 PHENOTYPES: - pink (2); white (2) - ratio 1:1

  6. NS = some of each SS = sickle cells NN = normal cells Codominance • The heterozygous condition, both alleles are expressed equally • Sickle Cell Anemia in Humans sick

  7. NS SS SS NS Problem: Codominance • Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (2) SS (2) - ratio 1:1 S S PHENOTYPES: - carrier (2); sick (2) - ratio 1:1

  8. Multiple Alleles • There are more than two alleles for a trait • Blood type in humans • Blood Types? • Type A, Type B, Type AB, Type O • Blood Alleles? • A, B, O (in book – IA, IB, I)

  9. Rules for Blood Type • A and B are codominant • AA = Type A • BB = Type B • AB = Type AB • A and B are dominant over O • AO = type A • BO = type B • OO = type O

  10. AO AO BO BO Problem: Multiple Alleles • Show the cross between a mother who has type O blood and a father who has type AB blood. O O GENOTYPES: - AO (2) BO (2) - ratio 1:1 A B PHENOTYPES: - type A (2); type B (2) - ratio 1:1

  11. BO AB AO OO Problem: Multiple Alleles • Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. GENOTYPES: A O • AB (1); BO (1); AO (1); OO (1) - ratio 1:1:1:1 B O PHENOTYPES: • type AB (1); type B (1) type A (1); type O (1) - ratio 1:1:1:1

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