Physical Maps Using Chromosomal Aberrations - Physical mapping of specific DNA sequences available in the form probes, can be achieved using chromosomal aberrations such as translocations, duplications and deletions.

For instance, the disease choroidermi or tapeto choroidal dystrophy (TCD) has been described in various patient having cytogenetically visible or submicroscopic deletions spanning the Xq21 band. This means that TCD locus must fall within the region these overlapping deletions.

TCD is an X-chromosome linked disorder retina and choroid, causing progressive right blindness and central blindness during the age of 20-40 years. In order to determine the location of TCD locus more precisely, several of these deletions were characterized with the help of several anonymous cloned DNA sequences from the proxima region of Xq'.