Recombination Frequency & Genetic Map Distance (cM)
Convert recombination counts ↔ genetic distance with linear, Haldane (−½ln(1−2r)) and Kosambi (¼ln((1+2r)/(1−2r))) map functions, SE of r, and interval summation with predicted r. Derived from Sturtevant 1913, Haldane 1919, Kosambi 1944, Griffiths. Educational use only.
Execution
Run this tool
Fill in the form, run the tool, and review the result in one place.
Samples
Examples that match this tool
Related
Continue with connected tools and hubs
Result
Ready for a run
Run the tool to preview files, text, structured data, or streamed output here.
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 Recombination Frequency & Genetic Map Distance calculator converts testcross counts into recombination frequency and genetic distance in centimorgans (cM), or sums map intervals and predicts the overall recombination frequency. It provides linear, Haldane, and Kosambi estimates, plus the standard error of r in counts mode. Educational use only.
When to use
Calculate recombination frequency from recombinant offspring and total progeny counts.
Compare linear, Haldane, and Kosambi genetic map distances in cM.
Add adjacent map intervals and estimate the recombination frequency across the full span.
How it works
1Choose Counts → recombination & map distance or Map intervals → total distance & predicted r.
2In counts mode, enter the recombinant count and total progeny; the calculator computes r as recombinant count divided by total progeny.
3The result reports linear distance and map-function estimates from Haldane and Kosambi, with the standard error of r.
4In intervals mode, enter comma-separated adjacent distances in cM; the calculator sums them and predicts r using the inverse Haldane and Kosambi functions.
Use cases
Teaching linkage, crossing-over, double crossovers, and genetic map functions in genetics courses.
Checking recombination calculations from testcross or offspring-count exercises.
Building a linkage-map span by summing adjacent cM intervals and comparing predicted recombination frequencies.
Examples
1. Estimate map distance from 18 recombinant offspring
Genetics student
Background
A testcross produces 18 recombinant offspring among 100 total progeny.
Problem
The student wants to compare the observed recombination frequency with map distances from three common mapping approaches.
How to use
Select Counts → recombination & map distance, enter 18 for Recombinant count and 100 for Total progeny, and choose 4 decimal places.
Recombinant count: 18; Total progeny: 100; Decimal places: 4
Outcome
The calculator reports r = 0.18, or 18%. The linear estimate is 18 cM, the Haldane estimate is 22.3144 cM, and the Kosambi estimate is 18.8443 cM.
2. Sum three linkage-map intervals
Genetics instructor
Background
A linkage map contains adjacent intervals of 5.2, 8.1, and 12.0 cM.
Problem
The instructor needs the total map span and the predicted recombination frequency across all three intervals.
How to use
Select Map intervals → total distance & predicted r and enter 5.2, 8.1, 12.0 in the Interval distances in cM field.
FAQ
What is recombination frequency?
Recombination frequency is the number of recombinant offspring divided by the total progeny, expressed as r or a percentage.
What units does the calculator use for genetic distance?
Genetic distance is reported in centimorgans (cM). One Morgan equals 100 cM.
What is the difference between the Haldane and Kosambi estimates?
Haldane assumes no interference, while Kosambi accounts for positive interference. For the same r, Haldane generally gives a larger distance than Kosambi.
Why can map distance exceed 50 cM when recombination frequency cannot?
Multiple crossovers can conceal recombination events, so r approaches 50% while mapping functions can estimate distances greater than 50 cM.
Can this calculator be used for clinical or diagnostic decisions?