The map distance between two genes, measured in centimorgans or map units, equals the percentage recombination frequency between the two genes--the likelihood of offspring with copies of those genes on the same chromosome that come from different parents.ave. dna image by Allyson Ricketts from Fotolia.com. The concept of map distance in a genotype refers to where genes are located on a chromosome but does not refer to physical distance; rather, map distance refers to the tendency for a crossover to occur between genes.