Trihybrid Cross Calculator - Punnett Square

A trihybrid cross tracks the simultaneous inheritance of three separate gene pairs, conventionally labeled as A, B, and C. Assuming the genes undergo independent assortment according to Mendel's law, we can analyze each gene locus separately and multiply their individual probabilities together. While a physical Punnett square for a trihybrid cross requires an immense 64-box grid (4 possible gametes from each parent multiplied together, i.e., 4 × 4 × 4), the mathematical shortcut relies on the product rule of probability. For any given allele combination, the chance of inheriting a specific genotype is the product of the probabilities of obtaining each individual gene pair: P(AabbCc) = P(Aa) × P(bb) × P(Cc).

Let us walk through a practical genetic cross between two parents who are heterozygous for all three traits: Parent 1 (AaBbCc) and Parent 2 (AaBbCc). First, we break down the cross for the first gene locus (Aa × Aa). The probability of an offspring being homozygous dominant (AA) is 1/4, heterozygous (Aa) is 1/2, and homozygous recessive (aa) is 1/4. Next, we look at the second locus (Bb × Bb) with the exact same probability breakdown. Finally, we look at the third locus (Cc × Cc). To find the probability of an offspring having the fully heterozygous genotype (AaBbCc), we multiply the individual probabilities: P(Aa) = 1/2, P(Bb) = 1/2, and P(Cc) = 1/2. Calculating this gives (1/2) × (1/2) × (1/2) = 1/8, or a 12.5% chance of occurrence in the total population.

When working with multi-trait inheritance problems, always verify whether the genes are located on separate chromosomes or if they exhibit genetic linkage. This calculator assumes independent assortment, meaning linked genes located close together on the same chromosome will yield different ratios due to crossing over. Additionally, double-check your parental input alleles for correct capitalization, as uppercase letters denote dominant alleles and lowercase letters represent recessive traits.