codominance

Question

Human ABO blood group inheritance displays which pattern between IA and IB alleles?

RankGuru · Accepted Answer

1. **Multiple Alleles**: The ABO blood group is controlled by gene $I$, which has three alleles: $I^A, I^B,$ and $i$.
2. **Dominance Relationships**:
   - Both $I^A$ and $I^B$ are completely dominant over $i$.
   - Between $I^A$ and $I^B$, **Codominance** is observed.
3. **Effect**: When an individual has both alleles ($I^A I^B$), both types of sugars (Antigen A and Antigen B) are expressed on the surface of red blood cells, resulting in Blood Group AB.
4. **Conclusion**: Neither allele masks the other; they are expressed together.

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codominance

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