Chromosome Walking and Characterization of Chromosome Segments
When a probe is used for the identification of a gene sequence in a genomic library, the probe may hybridize with a number of clones, each carrying a part of a large gene fragmented during preparation of genomic library. If we obtain partial digests (by digesting the DNA only partially) from the genome, different genomes (from large number of cells) may give fragments which have overlapping sequences, because sites cleaved in different genomes of the same organism, will differ being random. Since none of these fragments may have its entire sequence represented in the probe, overlapping sequences may be used to construct the original genomic sequence. Identification of fragments with an overlapping sequence may be a key to the reconstruction or characterization of large chromosome regions. This is achieved by the technique popularly called chromosome walking.