Three-stage approach of the Human Genome Project.
  1. Cytogenetic map Chromosome banding pattern and location of specific genes by fluorescence in situ hybridization ( FISH ).

  2. Genetic (linkage) mapping Ordering of genetic markers.

  3. Physical mapping Ordering of fragments cloned in phage and plasmid vectors; this gives the actual distance in base pairs between markers.

  4. DNA sequencing Determination of nucleotide sequence of each small fragment and assembly of the partial sequences into the complete genome sequence.