Linkage refers to the tendency of inhertance of the DNA sequences that are close together on a chromosome during the meiosis of sexual reproduction. It can be measured by the recombination frequency.
Recombination frequency describes the proportion of recombinant offsrpring produced in a genetic cross between two organisms. It is the frequency with which a single chromosomal cross over takesplace between two genes during the process of meiosis. Recombination frequency (RF) is given by
RF= Recombinants /total offspring x 100.
In the above example, the number of recombinant offspring is 20 and the total offspring is 400. By substituting these values,
RF= 20/400 x100
= 5.
The recombination frequency for the above cross is 5.