Eye Color Predictor Calculator
Model eye color inheritance using the two-gene Davenport model. Select the genotypes for both parents to predict the likelihood of blue, green, or brown eyes.
Parent Genotypes
Select eye color genotypes for Mother and Father. (B = Brown, G = Green, b = Blue).
4×4 Eye Color Punnett Grid
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Eye Color Probabilities
Offspring Eye Colors
Genotype Ratios
Expert Tip
Although eye color is polygenic (involving over 16 genes), the two-gene Davenport model provides a highly accurate approximation of inheritance using Bey2 and Gey.
Methodology & Equations
The Two-Gene Model
Eye color is modeled using two chromosome loci:
- **Bey2:** Controls Brown (B) vs. Blue (b). Brown is dominant to Blue.
- **Gey:** Controls Green (G) vs. Blue (b). Green is dominant to Blue.
The Brown allele (B) on Bey2 is dominant over the Gey alleles. If a B allele is present, the eyes are brown.
Genotype-to-Phenotype Rules
Offspring phenotypes are determined as follows:
- **Brown:** Has at least one B allele (e.g. Bb GG, BB bb, Bb Gb).
- **Green:** Bey2 must be bb, and Gey must have at least one G allele (e.g. bb GG, bb Gb).
- **Blue:** Bey2 must be bb, and Gey must be bb (only genotype bb bb).
Predicting Offspring Eye Color: Step-by-Step
Here is a step-by-step example crossing heterozygous Brown (Bb Gb) and heterozygous Green (bb Gb) parents:
Determine Parental Gametes
- Parent 1 (Bb Gb) gametes: BG, Bb, bG, bb.
- Parent 2 (bb Gb) gametes: bG, bb, bG, bb. (Simplified: bG and bb).
Construct 4x4 Punnett Square
Place Parent 1 gametes on top and Parent 2 gametes on the side, then combine the alleles in the grid cells (e.g., crossing BG and bG yields Bb Gg, which results in Brown eyes).
Tally Phenotypes
Out of 16 combined cells:
- 8 cells contain B -> 50% Brown eyes.
- 6 cells are bb G_ -> 37.5% Green eyes.
- 2 cells are bb bb -> 12.5% Blue eyes.
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