The phenotype data for a three-point cross for abc and bcd is tabulated as follows:
By comparing the progeny details of the parental class and the double crossover class, the order of the four genes is a-c-b-d.
Recombination between a and c can be calculated in the following way:
Recombination between b and c in cross 1:
Recombination between b and c in cross 2:
The total distance would be:
Recombination between b and d: