Punnett Square Maker for Genetics Crosses

Alleles, dominant vs recessive, genotype vs phenotype

• An allele is one version of a gene; you inherit one from each parent. Alleles are written as letters — a capital letter for the dominant allele (A) and the same letter in lowercase for the recessive allele (a).
• A dominant allele is expressed whenever it is present; a recessive allele only shows when both copies are recessive (aa). So AA and Aa look the same outwardly, while aa looks different.
• The genotype is the allele pair itself (AA, Aa, or aa). The phenotype is the observable trait that genotype produces (for example, dominant vs recessive appearance). One phenotype can come from more than one genotype, which is why the two ratios differ.

Two ways to make a Punnett square here

• Precise mode: type both parent genotypes (for example Aa and Aa, or AaBb and AaBb). The tool derives each parent’s gametes, fills every cell with the correctly combined and ordered genotype, and computes the genotype and phenotype ratios automatically — accurate every time, with nothing to align by hand.
• AI illustration mode: describe the cross in plain English and the tool generates a polished, presentation-ready illustration with color-coded results and labels.
• Use Precise mode when correctness matters (homework, exams, lab reports); use AI mode when you want a styled graphic for slides or a handout.

Monohybrid vs dihybrid crosses

A monohybrid cross tracks one gene, so each parent has two alleles and produces two gamete types — the square is 2×2 with four cells. The textbook example is Aa × Aa, which yields a 1:2:1 genotype ratio (1 AA : 2 Aa : 1 aa) and a 3:1 phenotype ratio (dominant : recessive). A dihybrid cross tracks two genes at once. Each parent like AaBb produces four gamete types (AB, Ab, aB, ab) by combining one allele from each gene, so the square becomes 4×4 with sixteen cells. The dihybrid AaBb × AaBb gives the classic 9:3:3:1 phenotype ratio. This maker builds both the 2×2 and 4×4 squares from your genotypes.

How to use the Punnett square maker

• Enter the Parent 1 genotype — two letters for a monohybrid cross (Aa) or four for a dihybrid (AaBb).
• Enter the Parent 2 genotype using the same gene letters so the cross is valid.
• The tool derives the gametes, fills every cell with the combined offspring genotype (alleles sorted dominant-first, e.g. Aa not aA), and reads out the genotype and phenotype ratios.
• Download a clean, editable SVG to drop into a worksheet, slide, or report — or switch to AI mode for a styled illustration.

Genotype and phenotype ratios for genetics class

The two ratios a Punnett square produces are exactly what most genetics questions ask for. The genotype ratio counts how many cells fall into each allele combination — for Aa × Aa that is 1 AA : 2 Aa : 1 aa. The phenotype ratio groups genotypes by the trait they show: because both AA and Aa display the dominant trait, Aa × Aa gives a 3:1 dominant-to-recessive split. For a dihybrid cross the phenotype ratio is 9:3:3:1. Because this maker tallies the ratios directly from the filled grid, the numbers always match the square you see — handy for checking homework, building test-prep examples, or teaching Mendelian inheritance.