Incomplete Dominance

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Incomplete Dominance Codominance Multiple Alleles:

Incomplete Dominance Codominance Multiple Alleles In a nutshell!

Review: Dominant/Recessive:

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

Review Problem: Dominant/Recessive:

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 P p pp Pp Pp PP - PP (1); Pp (2); pp (1) - ratio 1:2:1 - purple (3); white (1) - ratio 3:1 GENOTYPES: PHENOTYPES:

Incomplete Dominance:

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

Problem: Incomplete Dominance:

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

Codominance:

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

Problem: Codominance:

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

Multiple Alleles:

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 – I A , I B , I)

Rules for Blood Type:

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

Problem: Multiple Alleles:

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

Problem: Multiple Alleles:

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. AB (1); BO (1); AO (1); OO (1) - ratio 1:1:1:1 type AB (1); type B (1) type A (1); type O (1) - ratio 1:1:1:1 GENOTYPES: PHENOTYPES: A O B O AB OO BO AO