Trihybrid Punnett Square Calculator for 3 Genes
What this trihybrid Punnett square calculator does
This calculator computes offspring genotype and phenotype probabilities for a trihybrid cross involving three independently assorting genes (A, B, C). It generates all valid gametes for each parent, combines them, and aggregates identical outcomes into a clean probability table.
Key assumptions
Independent assortment - The three genes assort independently (no linkage).
Complete dominance - For each gene, having at least one dominant allele (uppercase) produces the dominant phenotype.
How gametes are generated
For each gene, a parent produces alleles in gametes based on genotype:
Homozygous dominant (AA) - only A is produced.
Heterozygous (Aa) - A and a are produced with equal probability.
Homozygous recessive (aa) - only a is produced.
If a parent is heterozygous at \(n\) loci, the number of distinct gametes is:
\[\text{Gametes} = 2^n\]
How offspring probabilities are computed
Each offspring is formed by combining one gamete from each parent. For any specific combination:
\[\Pr(\text{offspring}) = \Pr(\text{gamete}_1)\times \Pr(\text{gamete}_2)\]
Multiple gamete pairs can lead to the same offspring genotype, so the calculator sums probabilities of identical genotypes to get the final result.
Genotypes and phenotypes
A genotype is reported per gene (AA, Aa, aa) and concatenated across genes (for example AaBbCc).
A phenotype is reported using:
Dominant - A-, B-, C- (at least one uppercase allele present)
Recessive - aa, bb, cc (no uppercase allele present)
For example, Aa bb Cc corresponds to phenotype A- bb C-.
Interpreting the results table
The results table lists all unique offspring genotypes, their phenotypes, and their probabilities. You can search, sort, export to CSV/Excel, and use Customize Columns to change which columns are visible and their order.
Example
With AaBbCc × AaBbCc, the phenotype classes follow the classic trihybrid ratio across 8 phenotype categories. The calculator shows the exact probabilities and also summarizes phenotypes in a ratio-like form derived from the computed weights.