co-dominance:
In co-dominant inheritance, two different alleles exhibiting two different phenotypes will result in a third phenotype in which the two phenotypes appear together, not as a blend, but as their individual phenotypes. Thus, both alleles influence the genetic trait as neither allele is dominant or recessive. As both alleles can be traced in the pedigree, it resembles the pattern of dominant inheritance, except for the fact that both alleles can be seen. Examples of co-dominant disorders include ABO blood group and alpha-1 antitrypsin deficiency.
Incomplete dominance:
In incomplete dominance, two different alleles with two different phenotypes result in the creation of a third phenotype which is a blend of the two parent phenotypes. It is easy to identify within a pedigree as the parents will both exhibit different characteristics and the offspring will exhibit characteristics that are halfway between their parents' traits. An example of incomplete dominance is Tay-Sach's Disease.