Source: https://guthlabs.ai/docs/instruments/punnett-based-trihybrid-multi-gene-probability-calculator/implementation/

instrument implementation / implementation-contract

# Punnett-based Trihybrid/Multi-gene Probability Calculator implementation

A source-bound implementation contract for Punnett-based Trihybrid/Multi-gene Probability Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-with-binding-errata

**Evidence ID**: t5-116

**Effect**: Computation or source lookup only

## Input and validation requirements

The plain product rule has no division-by-zero trap and no genuine multi-regime formula branch, but an implementation without strict validation can return Infinity for extreme inputs and can accept values outside the probability domain. Percentage-versus-fraction ambiguity can also produce invalid results if units are not explicit.

## Required corrections

````
[
  {
    "vector": 3,
    "field": "combined_probability(_percent)",
    "wrong": "0 / 0",
    "correct": "0.1 / 10",
    "cause": "working literally writes 0.20×0.50=0"
  }
]
````

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "number_of_loci": 3,
    "per_locus_probabilities": [
      0.25,
      0.5,
      0.25
    ]
  },
  "expected_outputs": {
    "combined_probability": 0.03125,
    "combined_probability_percent": 3.125
  },
  "working": "P = 0.25 × 0.50 × 0.25\n0.25 × 0.50 = 0.125\n0.125 × 0.25 = 0.03125\n0.03125 × 100 = 3.125%"
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/punnett-based-trihybrid-multi-gene-probability-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/punnett-based-trihybrid-multi-gene-probability-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/punnett-based-trihybrid-multi-gene-probability-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`

- `tranche errata record`