Calculadora de Quadrado de Punnett
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
Aa × Aa → 1 AA : 2 Aa : 1 aa
About this calculator
The Punnett Square Calculator is an educational tool that simulates a monohybrid cross between two heterozygous individuals (Aa × Aa). It calculates the expected genotypic ratios in the offspring, following Mendel's first law. The result shows that 25% of the offspring will be homozygous dominant (AA), 50% heterozygous (Aa), and 25% homozygous recessive (aa).
The operation is simple: the user inputs the parental genotypes (both Aa) and the calculator automatically builds the Punnett square by combining alleles from each gamete. The resulting square has four cells, each representing a possible combination. The tool then sums the frequencies and displays the percentages of each genotype.
This calculator is useful for biology students learning Mendelian genetics, teachers wanting to quickly demonstrate cross results, or anyone interested in understanding how simple hereditary traits are transmitted. For example, when studying pea seed color (yellow dominant over green), the Aa × Aa cross shows a 3:1 probability for the dominant phenotype.
Important caveats: the calculator assumes independent allele segregation and no incomplete dominance or codominance. For dihybrid crosses or those with more than two alleles, this tool is not suitable. Also, the probabilities are theoretical and may not exactly reflect small sample sizes.
Frequently asked questions
What does the 1:2:1 ratio mean?
It means that, on average, for every four offspring, one will be AA, two will be Aa, and one will be aa. This is the expected genotypic ratio in an Aa × Aa cross.
Can I use this calculator for crosses with more than one gene?
No, this calculator is only for monohybrid crosses (one gene with two alleles). For dihybrid crosses, look for a specific tool.
What if the parents are AA and aa?
In that case, all offspring will be Aa (100% heterozygous). The calculator currently only supports the Aa × Aa cross.
Does the calculator consider incomplete dominance?
No, it assumes complete dominance. In incomplete dominance, the heterozygote would have an intermediate phenotype, but here the Aa genotype is considered dominant.
Why are the percentages always 25%, 50%, and 25%?
Because the Aa × Aa cross always produces A and a gametes in equal proportions, resulting in these fixed genotypic frequencies for a gene with two alleles.