📊 Progeny Data (8 Phenotypic Classes)
| Phenotype | Count |
|---|---|
🧬 Gene Order
—
Total Progeny
0
Parental Types
—
Double Crossovers
—
Coincidence
—
Interference
—
📏 Genetic Distances
| Phenotype | Count |
|---|---|
A three‑point testcross is a genetic cross used to map the relative positions of three genes on a chromosome. By analyzing progeny counts, we can determine gene order, calculate recombination frequencies, and estimate interference. This tool updates results in real time as you adjust the data.
The two least frequent progeny classes (double crossovers) are compared with the parental types (most frequent). The gene that differs between them is the middle gene on the chromosome.
Recombination frequency between two genes = (single crossovers + double crossovers) / total progeny. Distances are given in centiMorgans (cM). Double crossovers are counted twice when calculating the outer distance to correct for underestimation.
Coefficient of coincidence = observed double crossovers / expected double crossovers. Interference = 1 – coincidence. It measures the degree to which one crossover inhibits another nearby.
The tool validates your data. If double crossovers are not the rarest, a warning appears because this violates the basic assumption of three‑point mapping. Check your phenotype assignments or counts.
Yes, you can type any symbols (e.g., v, ct, cv) into the phenotype column. The calculator treats them as distinct alleles and determines order automatically.