What is a Punnett square?

A table that combines parental gametes to show the expected genotype proportions of offspring.

How does the 1:2:1 ratio appear for one gene?

When both parents are heterozygous (Aa×Aa), counting the cells gives AA:Aa:aa = 1:2:1.

Does the 9:3:3:1 ratio always appear for two genes?

It is a classic case when both parents are AaBb, genes assort independently, and complete dominance is assumed. Different conditions yield different ratios.

What about linkage (non-independent assortment)?

Phase 1 assumes independent assortment. If linkage or recombination exists, expected ratios change.

Are my inputs sent anywhere?

All calculations run in your browser. Your data is not sent.

Punnett square generator (1- and 2-gene) | automatic ratios

How to use (3 steps)

Select an example or enter genotypes for Parent 1 and Parent 2.
Choose 1 gene (2×2) or 2 genes (4×4).
The Punnett square and ratios appear. You can copy a Markdown table or export CSV/LaTeX.

Two-gene mode assumes independent assortment. Phenotype ratios are guides assuming complete dominance.

Inputs (parent genotypes)

Example (preset)

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Parent 1 (e.g., Aa)

Display: —

Parent 2 (e.g., Aa)

Display: —

Display options

Show phenotype ratio (guide, complete dominance)

Show %

Show fractions (count/total)

Compact table (mobile)

Assumptions (independent assortment & complete dominance)

Two-gene mode assumes independent assortment. Phenotype ratios are guides based on complete dominance.

Results (Punnett square)

Parent 1 gametes

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Parent 2 gametes

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Combinations (cells)

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Selected

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Selecting a cell highlights it in the summary.

How it’s calculated

Generate parental gametes and combine them in a grid.
Count occurrences to compute genotype proportions (%/ratio).
Phenotype ratios are shown as guides assuming complete dominance and independent assortment.

This is a basic learning tool. Phase 1 does not handle linkage or special inheritance patterns.

FAQ

Does 9:3:3:1 always appear?

It is a classic case for AaBb parents with independent assortment and complete dominance. Different conditions yield different ratios.

Can I input Aa or aA?

Either is fine. The display is normalized to Aa.

Does it handle linkage or recombination?

Not in Phase 1 (independent assortment is assumed).

I want to paste the table into a report.

You can copy it as a Markdown table and paste directly (CSV/LaTeX also available).

Mendelian ratio chi-square test calculator
Compute χ², df, and p-value from observed counts and expected ratios with step-by-step output.

Comments

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