Pedigree Probability Tree — Offspring Disease Risk | Online Free Tool

Pedigree Probability Tree — Offspring Disease Risk | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Education
Input types: select, number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

Pedigree Probability Tree calculates offspring disease and carrier probabilities using Mendelian inheritance models. Choose autosomal recessive, autosomal dominant, or X-linked recessive inheritance, enter the father's and mother's probabilities, and receive a step-by-step probability result in JSON format. Educational use only.

When to use

Estimate affected-child and carrier probabilities for autosomal recessive pedigrees.
Calculate inheritance risk when both parents are affected heterozygotes under an autosomal dominant model.
Break down affected-son, affected-daughter, and carrier-daughter probabilities for X-linked recessive inheritance.

How it works

1Select an inheritance mode: autosomal recessive, autosomal dominant, or X-linked recessive.
2Enter the father's and mother's carrier or affected probabilities according to the selected mode.
3The tool applies Mendelian probability rules to calculate the relevant offspring outcomes.
4Choose the number of decimal places and review the returned result and probability breakdown.

Use cases

Teaching Mendelian inheritance with transparent probability-tree calculations.
Checking pedigree exercises involving cystic fibrosis or other autosomal recessive traits.
Studying sex-specific inheritance patterns such as hemophilia or color blindness.

Examples

1. Two cystic fibrosis carriers

Genetics student

Background

A student is reviewing the classic autosomal recessive 1:2:1 genotype ratio for two known carriers.

Problem

Find the probability of an affected child, a carrier child, and an unaffected non-carrier child.

How to use

Select "Autosomal recessive," set both parent probabilities to 1, and choose 4 decimal places.

{"inheritanceMode":"autosomal-recessive","fatherProbability":1,"motherProbability":1,"decimalPlaces":4}

Outcome

The result is P(affected child) = 0.25, P(carrier child) = 0.5, and P(unaffected non-carrier child) = 0.25.

2. Hemophilia risk from a carrier mother

Biology instructor

Background

An instructor is demonstrating X-linked recessive inheritance using a carrier mother and an unaffected father.

Problem

Show the separate risks for sons and daughters as well as the overall affected-child probability.

How to use

Select "X-linked recessive," set the father's affected probability to 0 and the mother's carrier probability to 1, then choose 4 decimal places.

FAQ

What inheritance patterns does the tool support?

It supports autosomal recessive, autosomal dominant, and X-linked recessive inheritance.

What do the parent probability fields mean?

Their meaning depends on the selected mode: carrier probability for recessive models and affected probability for the dominant model.

What does the autosomal recessive calculation return?

It returns the probabilities of an affected child, a carrier child, and an unaffected non-carrier child.

How does the X-linked recessive model report results?

It reports overall affected-child probability plus separate affected-son, affected-daughter, and carrier-daughter probabilities.

Can this replace genetic counseling?

No. The calculator is for educational use and does not replace professional genetic counseling or medical advice.

{"inheritanceMode":"x-linked-recessive","fatherProbability":0,"motherProbability":1,"decimalPlaces":4}

3. Autosomal dominant pedigree exercise

Genetics student

Background

A student is studying the stated autosomal dominant case in which both affected parents are assumed to be heterozygous.

Problem

Calculate the affected-child probability for two affected heterozygous parents.

How to use

Select "Autosomal dominant" and enter 1 for both parent affected probabilities.

{"inheritanceMode":"autosomal-dominant","fatherProbability":1,"motherProbability":1,"decimalPlaces":4}

Outcome

Under the tool's heterozygous-parent assumption, the affected-child probability is 0.75.

Pedigree Probability Tree — Offspring Disease Risk

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Two cystic fibrosis carriers

2. Hemophilia risk from a carrier mother

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3. Autosomal dominant pedigree exercise