Punnett Square
A Punnett square from the parents' genotypes: gametes, genotypic and phenotypic ratios, monohybrid, dihybrid and trihybrid crosses, sex-linked inheritance.
The Punnett square calculator solves monohybrid, dihybrid and trihybrid cross problems: it finds the parents' gametes, builds the square and gives the genotypic and phenotypic ratios of the offspring. A separate mode handles sex-linked inheritance (hemophilia, color blindness).
How to use it
Enter the parents' genotypes as pairs of letters, one pair per gene: Aa, AaBb, AABbCc. A capital letter is a dominant allele, a lowercase one is recessive. The order of genes does not matter.
- Complete dominance — the heterozygote Aa looks like AA. The phenotype is written as A_ (at least one dominant allele) or aa.
- Incomplete dominance — Aa is intermediate (pink snapdragons from red and white parents), so the phenotypic ratio equals the genotypic one.
Mendel's laws in the square
| Cross | Genotypes | Phenotypes |
|---|---|---|
| AA × aa | all Aa | uniformity (1st law) |
| Aa × Aa | 1 : 2 : 1 | 3 : 1 (segregation) |
| Aa × aa | 1 : 1 | 1 : 1 (test cross) |
| AaBb × AaBb | 9 genotypes | 9 : 3 : 3 : 1 (independent assortment) |
Example. AaBb × AaBb: each parent makes 4 kinds of gametes (AB, Ab, aB, ab), the square has 16 cells, and the phenotypic ratio is 9 : 3 : 3 : 1.
The calculator treats the genes as unlinked: they are inherited independently (Mendel's third law).
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