1. Incomplete Dominance
&
Codominance

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

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