Punnett Square Calculator

A rigorous tool for predicting the probability of offspring genotypes and phenotypes resulting from a genetic cross. Assumes simple Mendelian inheritance (complete dominance, independent assortment).

JavaScript Required: This interactive calculator requires JavaScript to function. To manually calculate a monohybrid cross (e.g., Aa x Aa): Draw a 2x2 grid. Place the alleles for parent 1 on top (A, a) and parent 2 on the left (A, a). Fill in the grid to find AA, Aa, aA, and aa.

Parent 1 Genotype (e.g., Aa or AaBb)

Parent 2 Genotype (e.g., Aa or AaBb)

Grid Result

Genotypic Frequencies

Phenotypic Ratios (assuming complete dominance)

Understanding the Mechanics

The Punnett square is a visual representation of Mendelian inheritance. It models the biological processes of meiosis (gamete formation) and fertilization.

Common Mistakes

Linking independent traits: For a dihybrid cross (AaBb x AaBb), gametes must contain one allele for each gene (AB, Ab, aB, ab), not two alleles of the same gene (AA, bb).
Ignoring linkage: This calculator assumes genes are on separate chromosomes (independent assortment). If genes are linked, typical Mendelian ratios (like 9:3:3:1) will be skewed.
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