Answer» | Co-dominance | Incomplete dominance | | The condition in which two alleles are able to express themselves independently when present together, that is, neither allele is dominant, or even partially dominant, over the other. | The condition in which none of the two contrasting alleles or factors is dominant, and the heterozygote F1 has a phenotype that is intermediate between its the two homozygous parents. | | For example, the AB blood group in human beings is characterized by the presence of both antigen A (IA ) and antigen B (IB) on the surface of RBCs. Another example is sickle cell anemia in which the allele for sickle cell hemoglobin HbS is codominant with allele for normal hemoglobin HbA . | For example, in plants like four O’ Clock (Mirabilis jalapa) red and white flowered plants are homozygous for different alleles of a colordetermining gene; and when these are crossed, they produce heterozygotes that have pink flowers. If F1 plants are self-pollinated, the plants of F2 generation are of three types red, pink and white flowered in the ratio of 1:2:1. |
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