alleryStart learning →In the human MN blood groups, what does a heterozygote express on its red blood cells?
ANeither the M nor the N antigen
BA new antigen unlike M or unlike N
COnly the antigen from the mother's allele
DBoth the M antigen and the N antigen
Answer & Solution
Correct answer: D. Both the M antigen and the N antigen
1. The M and N alleles are expressed as an M or N antigen on the surface of red blood cells.
2. Each homozygote expresses only its own antigen.
3. The MN blood groups are codominant, so heterozygotes express both alleles equally.
4. That means both the M antigen and the N antigen appear together on the cell surface.
5. No blended or novel antigen is produced, which is what separates codominance from incomplete dominance.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.2 Characteristics and Traits_
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