[Identification of marker chromosomes and translocations in man using a computerized diagnostic database and...

Cytogenetic analysis revealed five carriers of supernumerary marker chromosomes and two carriers of unbalanced chromosome translocations in patients of the medical genetic consultation clinic. A new method for exact identification of such chromosome rearrangements requiring additional molecular cytogenetic diagnosis was proposed. The method involves computer analysis of abnormal phenotypic traits with the use of diagnostic databases and fluorescent in situ hybridization (FISH) to DNA probes specific for the most probable computer-selected chromosome syndromes. On average, the method allowed the number of necessary DNA probes to be decreased four times. In the tested patients, supernumerary marker chromosomes were shown to be derived from chromosomes 2, 9, and 15, and translocations were identified as dic(Y;18) and ins(6;21). Limited possibilities of using the method when (1) a chromosome syndrome is not clearly defined in a diagnostic system or (2) phenotypic expression of a marker chromosome is not significant are discussed. Presumably, the method will allow a reliable estimation of the efficiency of various diagnostic systems.