The correct option is
A When IA and IB are present together, they express the same type of sugar.
The correct option is A:
Explanation of the correct option:
- The presence or absence of two surface antigens (chemicals that might trigger an immunological response) on RBCs, notably A and B, determines the ABO grouping.
- Two natural antibodies can be found in the plasma of different people (proteins produced in response to antigens).
- The gene I is in charge of ABO blood types. Sugar polymers protrude from the surface of the plasma membrane of red blood cells, and the kind of sugar is controlled by the gene.
- IA, IB, and i are the three alleles of the gene (I). Alleles IA and IB create a slightly different kind of sugar, whereas allele i produces no sugar at all.
- Each person has any two of the three I gene alleles since humans are diploid organisms. Over i IA and IB have complete dominance.
- When IA and i are both present, only IA expresses (since i do not create sugar), and when IB and i are both present, only IB expresses. However, due of co-dominance, when IA and IB are present together, they both express their own types of sugars.
Explanation of the incorrect option:
Option B:
IA, IB, and i are the three alleles of the gene (I). Alleles IA and IB create a slightly different kind of sugar, whereas allele i produces no sugar at all.
Option C:
IA, IB, and i are the three alleles of the gene (I). Alleles IA and IB create a slightly different kind of sugar, whereas allele i produces no sugar at all.
Option D:
Each person has any two of the three I gene alleles since humans are diploid organisms. Over i IA and IB have complete dominance.
Final answer: Due of co-dominance, when IA and IB are present together, they both express their own types of sugars.