Heredity, Natural Selection, and Evolution

Early Studies in Heredity

What is incomplete dominance and codominance?

Both incomplete dominance and codominance are also forms of inheritance—how certain genetic traits are expressed in offspring. Incomplete dominance is characterized by blending where neither trait is dominant. For example, if a long watermelon (LL) is crossed with a round watermelon (RR), it produces an oval squash (LR); a black animal (BB) crossed with a white animal (WW) results in a gray (BW) animal. Codominance is the instance in which both traits show—in other words, both alleles are dominant and both are expressed in the offspring. For example, the pink petal color in four-o’clock flowers and sickle-cell anemia in humans are all examples of codominance.


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