1. Incomplete Dominance
Incomplete Dominance: The heterozygous genotype produces a phenotype that falls in between the dominant trait and the recessive trait.

2. Example:
In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following:
1. Red and white RR x rr
Genotypic Ratio:
100% Rr
Phenotypic Ratio:
100% pink flowers
R R Rr r

3. Example:
In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following:
2. Red and pink RR x Rr
Genotypic Ratio:
50% RR % Rr
Phenotypic Ratio:
50% Red flowers, 50% Pink flowers
R R RR Rr R r

4. Rr rr RR Rr rr White and Pink rr x Rr r r R r Pink and Pink Rr x Rr
Genotypic Ratio:
50% Rr % rr
Phenotypic Ratio:
50% Pink flowers % White flowers
r r Rr rr R r
Pink and Pink Rr x Rr
Genotypic Ratio:
25% RR % Rr % rr
Phenotypic Ratio:
25% Red flowers % Pink flowers % White flowers
R r RR Rr rr R r

5. Codominance
Codominance: condition in which both alleles of a gene are expressed in heterozygous offspring.

6. Example 1:
In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.
Black cow and White cow BB x WW
B B
Genotypic Ratio:
100% BW
Phenotypic Ratio:
100% Spotted cow BW W

7. Example 1:
In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.
2. Black cow and Spotted cow BB x BW
B B
Genotypic Ratio:
50% BB % BW
Phenotypic Ratio:
50% Black cow % Spotted cow BB BW B W

8. Example 1:
In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.
3. Both Spotted cows BW x BW
Genotypic Ratio:
25 % BB % BW % WW
Phenotypic Ratio:
25% Black cow % Spotted cow % White cow
B W BB BW WW B W

9. Blood Type (phenotype)
Example 2:
In blood typing, the gene for type A and the gene for type B are codominant. The gene for type O is recessive.
Blood Type (phenotype)
Genotype A
AA or AO B
BB or BO AB O OO

10. AO Determine the possible blood types of the offspring when:
1. Mother is type O, Father is type A (homozygous)
O O
Genotypic Ratio:
100% AO
Phenotypic Ratio:
100% Type A Blood AO A

11. AA AB AO BO Determine the possible blood types of the offspring when:
2. Mother is type AB, Father is Type A (heterozygous)
Genotypic Ratio:
25 % AA % AO 25% AB % BO
Phenotypic Ratio:
50% Type A Blood % Type AB Blood 25% Type B Blood
A B AA AB AO BO A O

12. AB BO AO OO Determine the possible blood types of the offspring when:
3. Mother is type A (heterozygous), Father is type B (heterozygous)
Genotypic Ratio:
25 % OO % AO 25% AB % BO
Phenotypic Ratio:
25% Type O Blood 25% Type A Blood % Type AB Blood 25% Type B Blood
A O AB BO AO OO B O

13. AB Determine the possible blood types of the offspring when:
4. Mother is type B (homozygous), Father is type A (homozygous)
B B
Genotypic Ratio:
100% AB
Phenotypic Ratio:
100% Type AB Blood AB A