Incomplete dominance and codominance
In incomplete dominance the heterozygote looks like a blend of the two homozygotes. In codominance both alleles show fully and separately.
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Analogy
Mixing red and white paint (blend) versus a red and white striped shirt (both).
In practice
Snapdragons: red x white gives pink. Human AB blood type: both A and B markers are present.
Practice
Flashcards
- What is codominance?Both alleles are fully expressed in the heterozygote, as in AB blood.
Questions people ask
How is codominance different from incomplete dominance?
In incomplete dominance the heterozygote shows a new, in-between version, like pink flowers from red and white parents. In codominance both alleles are expressed separately in the same individual, such as a roan cow with red and white hairs, or AB blood with both A and B markers.
How does ABO blood type inheritance work?
Three alleles exist: I^A, I^B and i. I^A and I^B are codominant, and both are dominant to i. So I^A i gives type A, I^B i gives type B, I^A I^B gives type AB, and ii gives type O. Parents with A and B can have a child with O.