What map unit (Centimorgan) is adopted in the construction of genetic maps?

The map unit used in the construction of genetic maps is the centimorgan (cM).

A centimorgan (cM) is a unit of genetic distance that represents a 1% recombination frequency between two genes or genetic markers. It is a measure of the likelihood of recombination occurring between two loci during meiosis. One centimorgan is equivalent to a 1% chance that a crossover (recombination event) will happen between two genetic markers on the same chromosome.