1. Incomplete Dominance Neither allele is dominant
Heterozygotes are a blend of homozygous phenotypes = no distinct expression of either allele
F2 phenotypic and genotypic ratios are 1:2:1
Snapdragon/Four o’clock flower color
Eggplant color
Tay-Sachs disease

2. Animation showing incomplete dominance in F1 and F2 generations

3. Exercise to predict ratios in situations where there is incomplete dominance

4. Try these
In a plant species, if the B allele (blue flowers) and the W allele (white flowers) are incompletely dominant (b is light blue), what offspring ratio is expected in a cross between a blue-flowered plant and a white-flowered plant?
What would be the phenotypic ratio of the flowers produced by a cross between two light blue flowers?

5. Codominance Both alleles are equally dominant
Heterozygotes express both alleles = distinct expression of the gene products of both alleles can be detected
MN blood group
F2 genotype and phenotype ratios are 1:2:1
Genotype
Phenotype
LMLM M
LMLN MN
LNLN N

6. MN Blood group Codominance Animation

7. Try These
Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs together.
Predict the phenotypic ratios of offspring when a homozygous white cow is crossed with a roan bull.
What should the genotypes & phenotypes for parent cattle be if a farmer wanted only cattle with red fur?
A cross between a black cat & a tan cat produces a tabby pattern (black & tan fur together).
What pattern of inheritance does this illustrate?
What percent of kittens would have tan fur if a tabby cat is crossed with a black cat?