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Trihybrid Punnett square

Crossing AaBbCc with AaBbCc gives 64 equally likely offspring, 27 genotypes and the classic 27:9:9:9:3:3:3:1 phenotype ratio: the calculator builds the full 8 by 8 Punnett square and lists every genotype with its probability. Free in your browser.

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Worked example

If you enter

Parent1: AaBbCc
Parent2: AaBbCc

You get

Genes: A, B, C
Cross: AaBbCc x AaBbCc
Genotype count: 27
Genotype ratio: 1:2:1:2:4:2:1:2:1:2:4:2:4:8:4:2:4:2:1:2:1:2:4:2:1:2:1

A trihybrid Punnett square is the Mendelian diagram that turns two parental three-gene genotypes into the sixty-four equally likely offspring of a three-locus cross. Students, tutors, exam platforms, and breeding notebooks need the full genotype probability distribution without losing a heterozygous cell or mixing gene order. This trihybrid cross Punnett square calculator accepts the six-allele genotype of each parent, splits each parent into eight gametes by independent assortment, fills the classic eight-by-eight grid, and returns every observed offspring genotype with its count, probability, and percent. A genotype that is not exactly six valid alleles of three distinct genes is rejected as invalid input instead of a silently empty board.

What a trihybrid Punnett square computes

A trihybrid Punnett square asks one counting question: if each parent carries two alleles at each of three independently assorting genes and donates exactly one allele per gene to a gamete, what six-allele genotypes appear among the sixty-four equally likely offspring, and how often?

The eight gametes of the first parent become the row headers of an eight-by-eight grid; the eight gametes of the second parent become the column headers; each cell is the pair formed by one row gamete and one column gamete, with the two alleles at each locus written as a diploid pair. Because every cell is equally likely, the genotype probability is simply the number of cells that show that genotype divided by sixty-four.

Heterozygous cells are written with the dominant capital letter first at each locus, so aA and Aa collapse to the same pair and aA bB cC collapses to AaBbCc. Under Mendel's second law the three loci factor: each gene is a monohybrid 1:2:1 (or a collapsed 1:0 or 1:1) and the trihybrid genotype frequency is the product of the three single-locus frequencies.

That is why the classic heterozygous-by-heterozygous cross AaBbCc times AaBbCc fills twenty-seven genotypes, with AaBbCc itself occupying eight of the sixty-four cells (probability one eighth) and AABBCC occupying only one cell (probability one sixty-fourth). Complete-dominance phenotype at each locus then groups those twenty-seven genotypes into eight classes whose reduced ratio is twenty-seven to nine to nine to nine to three to three to three to one. Homozygous-dominant by homozygous-recessive fills every cell with the triple heterozygote, so the distribution collapses to a single genotype with probability one.

The diagram is not a population-genetics model and does not estimate allele frequencies across a herd; it is the Mendelian counting argument for one fertilisation at a time, which is exactly what homework, exam oracles, and three-trait breeding worksheets ask for when they say trihybrid Punnett square.

What you can do with it

Classroom trihybrid homework

Let students submit two parental genotypes such as AaBbCc and AaBbCc and check the twenty-seven genotype frequencies and the twenty-seven-to-nine-to-nine-to-nine-to-three-to-three-to-three-to-one phenotype ratio.

Exam and LMS auto-grading

Mark trihybrid Punnett-square items with a deterministic oracle that rejects a genotype that is not exactly six valid alleles and never invents extra cells.

Three-trait breeding checks

Compute Mendelian offspring fractions for a planned trihybrid mating before committing greenhouse space or a litter, without a spreadsheet that mangles six-letter genotypes.

FAQ

How do I compute a trihybrid Punnett square?

Send parent1 and parent2 as six-allele genotypes of three genes (for example AaBbCc and AaBbCc).

What happens if a genotype is not exactly six valid alleles?

A genotype must be six letters of three distinct genes such as AaBbCc, AABBCC, or aabbcc. A monohybrid pair, a dihybrid string, digits, or mixed pairs such as Ab are rejected and are not billed.

How are phenotype ratios decided in a trihybrid cross?

The calculator uses complete dominance at each locus. Any capital allele at a gene is dominant at that gene; only the homozygous recessive pair is recessive there. AaBbCc times AaBbCc therefore yields the classic 27:9:9:9:3:3:3:1 phenotype ratio.

Does this Punnett square handle monohybrid or dihybrid crosses?

A four-cell monohybrid board or a sixteen-cell dihybrid board is outside the contract; each parent must carry exactly six alleles.

How many different genotypes does AaBbCc × AaBbCc produce?

27 distinct genotypes among the 64 equally likely offspring. The most common is AaBbCc, which fills 8 of the 64 cells, or 12.5 %, while each fully homozygous genotype such as aabbcc appears in only one cell.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"parent1":"AaBbCc","parent2":"AaBbCc"}'

const res = await fetch("https://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "parent1": "AaBbCc",
    "parent2": "AaBbCc"
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "parent1": "AaBbCc",
    "parent2": "AaBbCc"
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"parent1":"AaBbCc","parent2":"AaBbCc"}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"parent1":"AaBbCc","parent2":"AaBbCc"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/bio/trihybrid-cross-punnett-square", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "parent1": "AaBbCc",
  "parent2": "AaBbCc"
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "bio.trihybrid_cross_punnett_square",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

Input contract, response fields, and validation errors

Each value must be exactly six valid alleles of three distinct genes — six Latin letters that form three diploid pairs such as AaBbCc, AABBCC, or aabbcc. Optional separators are accepted so Aa Bb Cc and Aa/Bb/Cc mean the same six alleles. Both parents must share the same three genes in the same order: AaBbCc times AaBbDd is not a trihybrid of one three-locus set and is rejected on the same rule. POST a JSON body with two required genotypes: parent1 and parent2. Short aliases work the same way: mother, p1, and genotype1 for the first parent; father, p2, and genotype2 for the second. Missing fields, empty strings, a two-allele monohybrid string, a four-allele dihybrid string, eight letters of a tetrahybrid, digits, and a pair of different gene letters such as Ab all fail with invalid_input and a message that the genotype is not exactly six valid alleles. On success the body echoes the normalised genotypes with the dominant allele first inside each pair, names the three genes, restates the cross, lists the eight gametes of each parent and the sixty-four square cells in row-major order, and reports every observed genotype and complete-dominance phenotype with its count, probability, and percent. genotype_ratio and phenotype_ratio are the counts reduced by their greatest common divisor, omitting types that did not appear so a uniform grid is reported as 1 rather than sixty-four-to-zero. offspring_count is always sixty-four. Failed validation is not billed; successful calls use prepaid KIT balance at the published $0.002 base price per item. Pair the JSON with your own drawing code if you need a printable eight-by-eight grid; this endpoint returns the cells and the full probability distribution, not an image, and it never invents a sixty-fifth cell or a monohybrid board.

Where a trihybrid Punnett square calculator earns its keep

Biology classrooms and tutoring platforms use a trihybrid cross Punnett square calculator so learners can check a three-gene mating for arbitrary parental genotypes without losing a heterozygous cell or swapping a locus. The calculator does not treat monohybrid or dihybrid boards, sex linkage, incomplete dominance, or lethal alleles — send two six-allele genotypes and read genotypes as the complete probability distribution for that one three-gene mating. Keep requests small, pin the rounded probabilities in tests, and you get reproducible frequencies for homework, LMS plugins, and edge workers without standing up a computer-algebra system of your own. Exam-prep generators need a deterministic oracle that marks wrong a genotype that is not exactly six valid alleles instead of silently returning an empty success payload a buggy grader might treat as a pass. Plant and animal breeding notebooks reduce a planned three-trait mating to parent1 times parent2 when they only need the Mendelian fractions before they commit greenhouse space or a litter; calling a tiny parse API avoids a spreadsheet that reformats AaBbCc as a date or splits the six letters across extra columns.

Technical questions

What does the trihybrid Punnett square calculator cost?

The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.

Read the full KIT documentation →

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