An example of codominance in the MN blood groups of humans (less famous than the ABO blood groups, but still important!). A person's MN blood type is determined by his or her alleles of a certain gene. An
LM
allele specifies production of an M marker displayed on the surface of red blood cells, while an
LN
allele specifies production of a slightly different N marker.
Homozygotes have only M or an N markers, respectively, on the surface of their red blood cells. However, heterozygotes have both types of markers in equal numbers on the cell surface.
A woman with type AB and type MN blood has a child with a man who has type O blood and type MN.
What are the odds their child will have type B and type M blood?