Epistasis Calculator

Epistasis occurs when one gene masks or modifies the expression of another — the Epistasis Calculator works out how two interacting genes combine to produce offspring phenotype ratios. Select your epistasis type (Complementary, Supplementary, Recessive, or Dominant), then enter the genotypes for Gene A and Gene B of each parent to see the phenotype ratio, along with dominant, epistatic, and recessive phenotype counts across the total offspring.

Enter genotype for first gene

Enter genotype for second gene

Enter genotype for first gene

Enter genotype for second gene

Display genotypic and phenotypic ratios

Show probability percentages for each phenotype

Results

Phenotype Ratio

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Dominant Phenotype

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Epistatic Phenotype

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Recessive Phenotype

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Total Offspring

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Results Table

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Frequently Asked Questions

What is epistasis in genetics?

Epistasis is a genetic interaction where one gene masks or modifies the expression of another gene. The masking gene is called epistatic, while the masked gene is hypostatic.

What are the different types of epistasis?

The main types are complementary epistasis (9:7 ratio), supplementary epistasis (9:3:4), recessive epistasis (9:3:4), and dominant epistasis (12:3:1). Each produces different phenotype ratios in F2 crosses.

How is complementary epistasis different from supplementary epistasis?

Complementary epistasis requires both genes to have dominant alleles for expression (9:7 ratio), while supplementary epistasis has one gene adding to the effect of another (9:3:4 ratio with different phenotype categories).

What does a 9:7 ratio indicate in genetic crosses?

A 9:7 ratio typically indicates complementary epistasis, where both genes must have at least one dominant allele to produce the wild-type phenotype. All other combinations result in the same mutant phenotype.

How do you calculate epistatic ratios?

Epistatic ratios are calculated by performing a dihybrid cross and then grouping phenotypes based on the type of gene interaction. The standard 9:3:3:1 ratio is modified according to the epistatic relationship.

Can epistasis affect more than two genes?

Yes, epistasis can involve multiple genes. However, two-gene epistasis is most commonly studied and provides the foundation for understanding more complex gene interactions.