Three-stage  approach  of  the  Human
   Genome Project.
<Li> Cytogenetic   map  Chromosome  banding  pattern  and  location  of
specific genes by fluorescence in situ hybridization ( FISH ).
<Li> Genetic (linkage) mapping Ordering of genetic markers.
<Li> Physical mapping Ordering of fragments cloned in phage and plasmid
vectors;  this  gives  the  actual  distance in base pairs between
markers.
<Li> DNA  sequencing Determination of nucleotide sequence of each small
fragment  and  assembly of the partial sequences into the complete
genome sequence.