Molecular markers can be considered to be sign posts along the chromosome of the species. So mapping molecular marker loci will give you a molecular map of the species similar to a genetic map. Several types of molecular markers can be used for these analyses. Restriction fragment length polymorphisms or RFLP were the first type applied to mapping and for many species, these are still the most often used molecular. Although the advent of RFLP launched the molecular mapping revolution, for species such as human their utility has about run its course.
Mapping requires polymorphisms between the individuals being mapped.
In humans, an informative RFLP, that is one that maps near a gene of interest, may exist for one population but not be useful for a second population. Therefore the molecular marker was only good in that one population. This extends the usefulness of any one specific marker linked to a gene to many human populations. The core of the VNTR is a sequences usually 15-100 base pairs long. What makes these sequences particularly useful is that during evolution the core sequence under went tandem duplication and dispersal throughout the genome.