Biol 222 - lecture 6 - extensions on basic principles. Dominance - the phenotype of the heterozygote (aa) is the same as the homozygote (aa) Co-dominance - the phenotype of the heterozygote (aa) includes the phenotypes of both of the homozygotes (aa and aa: example - fur colors. Aa is black fur aa is white fur. Aa is patches of white and black fur. Incomplete dominance - the phenotype of the heterozygote (aa) is an intermediate between the homozygotes (mix between aa and aa: example - flower color. Aa is a white flower aa is a red flower. Incompletely dominant with respect to sickle cell shaped red blood cells. Co-dominant because both hemoglobin molecules hba and hbs are present: hbs is an example of a pleiotropic allele. Pleiotropic allele - an allele affects more than one characteristic. In this case anemia and sickle cell red blood cells.