Can this tool handle more than three genes?

No, this tool is specifically designed for 2-gene (dihybrid) and 3-gene (trihybrid) crosses.

What is the difference between the Punnett square and the forked-line diagram?

The Punnett square displays the full grid of allele combinations, while the forked-line diagram uses branching probability lines to calculate multi-gene ratios without a large grid.

How do I specify incomplete dominance or codominance?

Add [incomplete] or [codominance] at the end of your gene definition line, for example: Flower = R,W [incomplete].

What happens if I enter invalid parent genotypes?

The tool requires parent genotypes to match the allele letters declared in your gene definitions; mismatched letters will cause calculation errors.

How are the phenotype ratios sorted?

You can sort the genotype and phenotype ratio lists either by frequency (highest percentage first) or alphabetically.

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Punnett Trihybrid & Dihybrid Cross Visualizer

Compute 2-3 gene Mendelian crosses with a full Punnett square and forked-line branch diagram. Supports complete, incomplete and codominance inheritance.

Details

What this tool helps you do

Compute 2-gene (dihybrid) and 3-gene (trihybrid) Mendelian crosses with a full Punnett square AND a forked-line (branch) diagram.

This extends the Mendelian Punnett Square tool to multiple loci: that tool handles single-gene crosses, this one handles 2-3 genes simultaneously.

How to use

Declare each gene on its own line: Trait = Allele1,Allele2 [mode]

mode is optional, default complete. Choices: complete / incomplete / codominance.
Example: Seed color = Y,y · Seed shape = R,r [complete] · Flower = R,W [incomplete]

Enter both parents' genotypes, e.g. YyRr (dihybrid) or AaBbCc (trihybrid). The tool matches allele letters to each declared gene.
Choose the display: Punnett square + ratios, forked-line branch diagram, or both.

What you get

Punnett square: the full 2ⁿ × 2ⁿ grid (4×4 for dihybrid, 8×8 for trihybrid).
Forked-line diagram: the branch method showing how each gene's monohybrid ratio (e.g. 1:2:1) multiplies into the final multi-gene distribution — the classic way to solve trihybrid crosses without drawing a 64-cell grid.
Genotype ratio: every unique genotype tallied with count and percentage.
Phenotype ratio: after applying each gene's inheritance mode (complete/incomplete/codominance).

Inheritance modes

Complete: uppercase allele masks lowercase (Aa looks like AA).
Incomplete: heterozygote is a blend (RW → "RW-blend", e.g. pink flowers from red + white).
Codominance: both alleles expressed (AB blood type, spots).

Execution

Run this tool

Fill in the form, run the tool, and review the result in one place.

Prepared example runs

Click an example to fill the form automatically. File inputs still need an upload.

2 examples

Classic dihybrid: YyRr × YyRr

Seed color × seed shape. Classic 9:3:3:1 phenotype ratio.

<div class="pt-wrap">Dihybrid YyRr × YyRr → 4×4 Punnett square. Phenotype ratio 9 yellow-round : 3 yellow-wrinkled : 3 green-round : 1 green-wrinkled.</div>

Trihybrid: AaBbCc × AaBbCc

Three independent genes, all complete dominance. 27:9:9:9:3:3:3:1 ratio.

<div class="pt-wrap">Trihybrid AaBbCc × AaBbCc → 8×8 Punnett (64 cells). Forked-line shows 1:2:1 per gene multiplying to 27 genotype classes. Phenotype ratio 27:9:9:9:3:3:3:1.</div>

Inputs

Set the required fields, then run the tool.

5 options

ContentPaste or type the main input values.3

Genes (one per line: Trait = Allele1,Allele2 [mode])textareaRequiredDeclare 2 or 3 genes, one per line. Format: Trait = Allele1,Allele2 [mode]. Mode is optional (default complete).Parent 1 genotype (e.g. AaBb or AaBbCc)textRequiredParent 1 genotype. Use the same letters as declared in the genes above.Parent 2 genotypetextRequiredParent 2 genotype.

SettingsAdjust formats, ranges, numbers, and modes.2

DisplayselectOptionalBoth shows the full grid and the branch diagram. Punnett shows only the grid + ratios. Forked shows only the branch method.SortselectOptionalHow to sort the genotype and phenotype ratio lists.

Result

Ready for a run

Run the tool to preview files, text, structured data, or streamed output here.

Samples

Punnett Trihybrid & Dihybrid Cross Visualizer

What this tool helps you do

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Prepared example runs

Inputs

Result

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Prepared example runs

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Key facts

Overview

When to use

How it works

Use cases

Examples

1. Classic Pea Plant Dihybrid Cross

2. Trihybrid Cross with Mixed Inheritance Modes

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