Incomplete Dominance & Codominance

Codominance red white roan Defined: When both alleles are dominant and equally expressed The colors do NOT blend together, but are equally seen Ex: Cattle Coat Red cow x White cow = Roan Cow Ex: Human Blood types Type A x Type B = Type AB red white roan

Blood Types Human blood type has 3 alleles Dominant A allele Dominant B allele Recessive O allele A and B allele are equally codominant Codominant blood type

Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood. List the genotypes. 100%AB List the phenotypes. 100% type AB blood B B A A B A B A B A B

Ex: Mike is heterozygous for type A blood and Lisa is heterozygous for type B blood. List the genotypes. 25%AB 25%Ao 25%Bo 25%oo List the phenotypes. 25% type AB blood 25% type A blood 25% type B blood 25% type o blood Probability of Heterozygous individual? 75% B o A o A B A o B o o o

Incomplete Dominance Red (RR) White (WW) Pink (RW) Defined: Neither allele is completely dominant Heterozygous = blended appearance More than 2 different phenotypes can occur Ex: Many flower colors

List the genotypes possible. 100% RW List the phenotypes possible. Example: Cross an incomplete homozygous dominant red carnation (RR) with an incomplete homozygous white carnation (WW). List the genotypes possible. 100% RW List the phenotypes possible. 100% Pink W W R W R W R pink pink R W R W pink pink

R W R W W W W pink white R W W W pink white Example: Cross one heterozygous pink (RW) carnation with a white carnation (WW). List the genotypes possible. 50% RW 50% WW List the phenotypes possible. 50%Pink 50%White R W R W W W W pink white R W W W pink white

Incomplete vs. Codominance Codominance: Both equally expressed Red flowers + White flowers = Incomplete Dominance: alleles blend