The document discusses two genetic concepts: incomplete dominance and codominance. In incomplete dominance, the heterozygous genotype produces an intermediate phenotype between the two homozygous genotypes. For example, in flowers red and white petal color show incomplete dominance, where heterozygotes are pink. Codominance occurs when both alleles are fully expressed in the heterozygote. For example, in cattle black and white coat colors are codominant, where heterozygotes are spotted. The document provides examples calculating genotypic and phenotypic ratios for offspring from crosses involving these inheritance patterns.

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

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:
Genotypic Ratio:
Phenotypic Ratio:
1. Red and white ______ x _______

3. Example:
Red results when a flower has homozygous dominant
A flower that is heterozygous for this trait will be pink. Predict the
genotypic and phenotypic ratios of the offspring for the following:
Genotypic Ratio:
Phenotypic Ratio:
2. Red and pink _______ x ________

4. Genotypic Ratio:
Phenotypic Ratio:
Genotypic Ratio:
Phenotypic Ratio:
White and Pink
Pink and Pink

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.
1. Black cow and White cow ______ x ______
Genotypic Ratio:
Phenotypic Ratio:

7. .
2. Black cow and Spotted cow _______ x ______
Genotypic Ratio:
Phenotypic Ratio:

8. Example 1:
3. Both Spotted cows ______x ________
Genotypic Ratio:
Phenotypic Ratio:

9. Example 2:
In blood typing, the gene for type A (IA ) and the gene for type B (IB )
are codominant. The gene for type O is recessive (ii). Genotypes are
written IB or IA or i
Blood Type (phenotype) Genotype
A IAIA or IAi
B IBIB or IBi
AB IAIB
O ii

10. Determine the possible blood types of the offspring when:
1. Mother is type O (ii), Father is type A (IA IA) (homozygous)
Genotypic Ratio:
Phenotypic Ratio:

11. Determine the possible blood types of the offspring when:
Genotypic Ratio:
Phenotypic Ratio:
2. Mother is type AB, Father is Type A (heterozygous)