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Punnett Square - Free Online Genetics Lab Tool | IconVault

Build interactive Punnett squares: pick parent genotypes, see genotype and phenotype ratios with step-by-step explanations. Free, runs in your browser.

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Punnett Square

Genotype and phenotype ratios with step explanations

5 of 5 free uses left

A = dominant allele, a = recessive allele

The square

A
a
A
AA
Aa
a
Aa
aa

Green boxes show the dominant trait, amber shows the recessive trait.

Ratios

Genotypic ratio

AA

1/4

25%

Aa

2/4

50%

aa

1/4

25%

Phenotypic ratio

Dominant

3/4

Recessive

1/4

How it works

  1. 1Write the parent genotypes: Parent 1 is Aa, Parent 2 is Aa.
  2. 2Split each parent into its two gametes. Parent 1 makes A and a; Parent 2 makes A and a.
  3. 3Fill the 2x2 grid: each box combines one gamete from each parent.
  4. 4Count genotypes: AA appears 1/4, Aa appears 2/4, aa appears 1/4.
  5. 5Apply complete dominance: any genotype with A shows the dominant trait, so 3/4 dominant and 1/4 recessive.
  6. 6As ratios, that is 1 : 2 : 1 genotypic and 3 : 1 phenotypic.

5 of 5 free copies left.

Simplified model: this lab assumes complete dominance of one gene with two alleles. Real traits often involve incomplete dominance, codominance, multiple genes or environmental effects.

About this tool

IconVault's Punnett Square lab builds a 2x2 Punnett square from the genotypes you pick for each parent. Choose AA, Aa or aa for Parent 1 and Parent 2, and the square fills in live with gametes along the edges, color-coded offspring boxes, genotypic ratios (AA, Aa, aa as fractions and percents) and phenotypic ratios (dominant vs recessive). A step-by-step walkthrough explains how the gametes, counts and ratios were derived.

It is free and runs fully in your browser, and you can copy the full result including the steps. The honest limit: it models one gene with two alleles under complete dominance. Real traits often involve incomplete dominance, codominance, multiple genes or environmental effects, which this lab does not cover.

Frequently asked questions

Popular searches

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