Genetic Linkage & Recombination Frequency Calculator
Analyze genetic linkage from testcross progeny counts. Input observed offspring counts for parental and recombinant phenotypes to calculate map distance in centimorgans (cM).
Offspring Phenotype Counts
Enter observed counts for parental (non-crossover) and recombinant (crossover) offspring.
Parental Types (Most Common)
Recombinant Types (Least Common)
Linkage Analysis
Expert Tip
If the recombination frequency approaches 50%, the genes are either on different chromosomes or very far apart on the same chromosome, and behave as if they are unlinked (independent assortment).
Methodology & Equations
Recombination Frequency Formula
Recombination frequency represents the percentage of crossover events during meiosis:
Centimorgans (cM)
One centimorgan (cM) is defined as the genetic distance over which 1% of offspring products are recombinant. Therefore, a Recombination Frequency of 8% corresponds directly to a genetic map distance of 8 cM.
How to Calculate Genetic Linkage: Step-by-Step
Below is a step-by-step example using observed counts of 450 and 470 parental offspring, along with 42 and 38 recombinant offspring:
Sum the Total Progeny
Add all observed individuals: Total = 450 + 470 + 42 + 38 = 1,000 offspring.
Sum the Recombinants
Add the counts for the crossover/recombinant categories: Recombinants = 42 + 38 = 80 offspring.
Divide and Express as Percentage
Divide recombinants by total and multiply by 100:
RF (%) = (80 / 1,000) × 100 = 8.0%.
This corresponds directly to 8.0 cM of genetic distance. Since 8.0% < 50%, the genes are genetically linked.
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