Frequency of recombination
The frequency with which loci recombine depends on how far apart they are on the chromosome (loci on separate chromosomes cannot be linked). Usually (but not always*) physical distance is closely related to linkage - loci which lie close together are more likely to remain linked. The number of recombination events observed among the progeny gives a measure of the distance between two loci. Thus recombination percentage = 100 x (no. of recombinants / total no. of progeny).
* Some areas of the genome may have more or less recombination than expected; for example, the region either side of the centromere often has an unexpectedly low level often have very low levels of recombination