Incomplete Dominance Calculator
Model genetic crosses where the heterozygous genotype results in a third, blended phenotype (e.g., crossing red flowers and white flowers yields pink flowers).
Alleles & Parental Genotypes
Customize your alleles and phenotypes, then select parent genotypes.
Incomplete Dominance 2×2 Grid
| R | W | |
|---|---|---|
| R | RR | RW |
| W | RW | WW |
Trait Probabilities
Genotype Ratio
Phenotype Ratio (Blended)
Expert Tip
In incomplete dominance, heterozygous offspring exhibit a blend of parent phenotypes. For example, crossing Red (RR) and White (WW) flowers produces Pink (RW) flowers because neither allele is completely dominant.
Methodology & Equations
Blended Phenotypes
Under the incomplete dominance model, the heterozygous genotype produces a diluted or intermediate phenotype:
- **Homozygous 1 (e.g. RR):** Full expression of Phenotype 1 (Red).
- **Heterozygous (e.g. RW):** Intermediate, blended phenotype (Pink).
- **Homozygous 2 (e.g. WW):** Full expression of Phenotype 2 (White).
Genotype & Phenotype Ratios
Crossing two heterozygous (Pink / RW) plants results in a 1:2:1 ratio for both genotypes and phänotypes:
- 25% Red (RR)
- 50% Pink (RW)
- 25% White (WW)
This differs from complete dominance, where heterozygous individuals display the dominant phenotype (resulting in a 3:1 phenotypic ratio).
How to Predict Incomplete Dominance: Step-by-Step
Below is a step-by-step example crossing a Red parent (RR) with a Pink parent (RW):
Determine Parent Alleles
Parent 1 (RR) can only pass on the R allele. Parent 2 (RW) can pass on either R or W.
Fill the 2x2 Punnett Square
Place Parent 1 alleles (R, R) on top, and Parent 2 alleles (R, W) on the left side:
Top Row Cells: RR, RR.
Bottom Row Cells: RW, RW.
Determine Phenotypes
Analyze the offspring genotypes:
- 50% RR translates to 50% Red flowers.
- 50% RW translates to 50% Pink flowers (blended phenotype).
Related Calculators
View All Biology Tools →Punnett Square Calculator
Generate custom 2x2 Punnett squares and calculate genotype probabilities.
Codominance Calculator
Model genetic crosses where both alleles are co-expressed in heterozygotes.
Monohybrid Cross Calculator
Predict genotype and phenotype ratios for single gene traits with complete dominance.