Epistasis Ratio Calculator (modified dihybrid ratios)

Epistasis Ratio Calculator (modified dihybrid ratios) | 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, text
Output type: json
Sample coverage: 4
API ready: Yes

Overview

The Epistasis Ratio Calculator computes expected F2 phenotypic ratios and counts for an AaBb × AaBb cross under independent assortment or six common two-locus interaction models: 9:7, 9:3:4, 12:3:1, 13:3, 15:1, and 9:6:1. Enter optional observed phenotype counts to perform a chi-square goodness-of-fit test. Educational use only.

When to use

Calculate expected phenotype counts from a selected modified dihybrid ratio and total F2 offspring.
Compare observed phenotype counts with an independent 9:3:3:1 expectation or an epistasis ratio.
Review whether observed counts show a significant chi-square deviation from the selected theoretical ratio.

How it works

1Select the interaction type, such as complementary genes, recessive epistasis, or no interaction.
2Enter the total number of F2 offspring to convert ratio parts into expected phenotype counts.
3Optionally enter comma-separated observed counts in the same order as the phenotype classes.
4The calculator returns JSON with the ratio, phenotype classes, expected counts, and optional chi-square goodness-of-fit results.

Use cases

Teaching how two-locus gene interactions modify the classic Mendelian dihybrid ratio.
Estimating phenotype counts for classroom genetics exercises and F2 cross planning.
Testing example breeding data against a proposed epistasis model with chi-square goodness of fit.

Examples

1. Calculate a 9:7 complementary-gene expectation

Genetics student

Background

A student is studying complementary gene action in sweet peas and wants expected flower-color counts for 160 F2 offspring.

Problem

Convert the 9:7 ratio into expected colored and white phenotype counts.

How to use

Select Complementary genes (9:7), enter 160 for Total F2 offspring, and leave observed counts blank.

{"interactionType":"complementary","totalOffspring":160,"decimalPlaces":4}

Outcome

The calculator returns 90 colored offspring and 70 white offspring, corresponding to 56.25% and 43.75% of the F2 total.

2. Test Mendelian dihybrid data against 9:3:3:1

Biology instructor

Background

An instructor uses Mendel's seed shape and color counts: 315 round yellow, 108 wrinkled yellow, 101 round green, and 32 wrinkled green, for a total of 556.

Problem

Determine whether the observed counts fit the no-interaction 9:3:3:1 expectation.

How to use

Select No interaction (9:3:3:1), enter 556 as the total, and enter observed counts as 315, 108, 101, 32.

FAQ

What cross does the calculator use?

It models an AaBb × AaBb F2 cross with two loci.

Which ratios are supported?

It supports 9:3:3:1, 9:7, 9:3:4, 12:3:1, 13:3, 15:1, and 9:6:1.

What should I enter for total F2 offspring?

Enter the total number of F2 individuals used to calculate expected counts.

How do I enter observed counts?

Enter comma-separated counts, one for each phenotype class, following the listed class order.

Is the calculator intended for clinical or research decisions?

No. It is provided for educational use only.

{"interactionType":"independent","totalOffspring":556,"observedCounts":"315, 108, 101, 32","decimalPlaces":4}

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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. Calculate a 9:7 complementary-gene expectation

2. Test Mendelian dihybrid data against 9:3:3:1

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3. Compare observed counts with recessive epistasis