Blood groups are due to carbohydrates on RBC surfaces produced by blood group gene with 3 alleles:  A,  B,  &  i
	i allele adds no sugar on RBC cell surfaces
	A allele adds sugar galactosamine to RBC surface
	B allele adds sugar galactose to RBC surface
	A and B allele each produce a sugar                               galactosamine & galactose.