Molecular detection and differentiation of deletions in band 13q14 in human retinoblastoma.

Five cloned DNA segments within or adjacent to human chromosome band 13q14 were mapped by a combination of in situ hybridization and DNA dosage blotting. The DNA was isolated from human retinoblastoma patients with deletions varying in size and precise location. One of these deletions occurred in mosaic form, requiring T-cell cloning to obtain cells uniformly containing the deletion and useful for blotting. Regions of overlap between the intervals on chromosome #13 deduced for each probe from the two different mapping methods permitted a more precise location for each, from which a physical ordering of these five probes could be obtained. This ordered set of probes constitutes the start of a grid spanning band 13q14 of potential use in the diagnosis and understanding of human retinoblastoma.