Blood Type O

Blood type O is the most common blood type. This phenotype can only occur when both alleles are recessive O type. Group O can donate red blood cells to anybody. It's usually the universal donor.

Blood Type B

Blood type B is a phenotype that can present itself when there is at least one B allele genotype present. Both A and B alleles are known to be dominant over O.

Blood Type A

Blood type A is a phenotype that can present itself when there is at least one A allele genotype present. Both A and B alleles are known to be dominant over O.

Blood type AB

Blood type AB is a phenotype that can present itself when both dominant alleles A and B are present together, as a co-dominant trait. Blood type AB phenotype is usually the universal accepter.