Punnett Square Generator
Generate a Punnett square for one or more genes, with genotype and phenotype ratios, and the caveats about what simple Mendelian prediction cannot account for.
Last reviewed by the Radiatus Cloud team
Need this done properly for your business?
Radiatus delivers secure cloud, DevOps & compliance engineering.
The square enumerates every combination
A Punnett square lists the gametes each parent can produce along the two axes and fills each cell with the combination, which makes the offspring ratios visible by counting rather than by calculation. For a single gene with two alleles there are four cells and the familiar three to one ratio falls out immediately. The method is a bookkeeping device rather than a model, and its clarity is why it survives as the standard teaching tool.
Each additional gene multiplies the square
Two genes give sixteen cells, three give sixty-four, and four give two hundred and fifty-six. The independent assortment that makes this multiplication valid holds only when the genes are on different chromosomes, or far enough apart on the same one that crossing over separates them freely. Linked genes do not assort independently and a Punnett square built as though they do gives the wrong answer.
Simple dominance is the exception rather than the rule
Most traits are not controlled by one gene with one dominant allele. Height, skin colour and most disease risks are polygenic, involving many genes each contributing a small amount. Incomplete dominance, codominance, multiple alleles, sex linkage and environmental effects all break the simple model. The square remains correct for the cases it describes and those cases are a small part of inheritance.
Related tools
- Security Term Translator — Translate complex security jargon into business language.
- Security Myth vs Reality — Fact-check common security myths.
- Breach News Impact — Contextualize major breaches into understandable analogies.
- Config Safety Analyzer — Paste a config snippet to check for obvious safety issues.
Frequently Asked Questions
What does the ratio actually predict?
The probability for each offspring independently, not the outcome of a specific set. A three to one ratio means each offspring has a three in four chance, so four offspring can easily come out four to zero.
When does independent assortment fail?
When genes sit close together on the same chromosome, so they tend to be inherited together. A Punnett square assumes free assortment, and for linked genes the real ratios differ, with the difference depending on how far apart they are.
What is incomplete dominance?
Where the heterozygote shows an intermediate phenotype rather than the dominant one, as in a red and white cross giving pink. The genotype ratio is unchanged and the phenotype ratio becomes one to two to one instead of three to one.
Can this predict human traits?
Rarely. Eye colour, height and most disease risks are polygenic, involving many genes each contributing a little, plus environmental effects. Single-gene conditions do follow these patterns, which is where the method is genuinely used.
Why is my square so large?
Because each additional gene multiplies the number of gamete combinations by four. Two genes give sixteen cells and three give sixty-four, which is why crosses beyond two genes are usually calculated rather than drawn.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter the parent genotypes to see the offspring square and ratios.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.