1 cM is equivalent to
One centimorgan equals one percent of meioses where crossover occurs between two markers producing one percent recombinant chromosomes when intervals short and interference negligible. Physical base pair equivalent varies: average human one centimorgan approximates one megabase but fluctuates with hotspot distribution along chromosome. Over longer intervals double crossovers obscure true exchange count requiring Haldane or Kosambi mapping functions for correction. Understanding conversion underlies linkage map construction, quantitative trait locus mapping and genetic counselling for recombination risk estimation between disease locus and marker loci.
Ref: Griffiths et al., Introduction to Genetic Analysis, 12th ed., Chapter 5: Map Unit Equivalence One Percent Recombination