Recombination Frequency Calculator
Calculate recombination frequency (map distance) between two genes from testcross data. Convert between recombination frequency and centiMorgans (cM) for genetic mapping.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Recombination Frequency Calculator | — | RF = (recombinants)/(total offspring) × 100 | cM (centiMorgans) |
Step-by-Step Examples
Testcross offspring: 206 parental types + 48 recombinant types = 254 total. Wait, let me set up: Total 400: 176 PQ, 176 pq (parental), 24 Pq, 24 pQ (recombinant).
- Recombinants = 24 + 24 = 48
- Total = 400
- RF = 48/400 x 100 = 12 cM
- Genes are 12 cM apart on the linkage map
40 recombinants out of 1000 total.
- RF = 40/1000 x 100 = 4 cM
- Very closely linked
- Low chance of recombination between them
500 recombinants out of 1000 (all combinations equally frequent).
- RF = 500/1000 x 100 = 50%
- 50% recombination = independent assortment
- Genes appear to be on different chromosomes or very far apart
Real-World Applications
Common Mistakes to Avoid
Genes are either linked (RF < 50%) or unlinked (RF = 50%). RF > 50% is impossible; genes become independent at 50%.
Double crossovers restore parental combinations (appear as non-recombinants). Kosambi or Haldane mapping functions correct for double crossovers.
RF calculation requires a testcross (unknown x homozygous recessive) so all gametes of the unknown parent are visible in offspring.