Respuesta :

Map Distance can be defined as the expression of the probability that crossing over will occur between two genes (loci) and it is measured as a Centimorgan (cM).  
1 Centimorgan  or 1 map unit is equivalent to 1% crossing over. So if recombinant frequency between genes Dand B is 32%, the distance between them is 32 map units or 32 cM.