IDENTIFICATION OF MARKER CHROMOSOMES AND TRANSLOCATIONS BY MEANS OF ADIAGNOSTIC DATABASE AND FLUORESCENT IN-SITU HYBRIDIZATION

Cytogenetic analysis revealed five carriers of supernumerary marker ch romosomes 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 addit ional molecular cytogenetic diagnosis was proposed. The method involve s computer analysis of abnormal phenotypic traits with the use of diag nostic databases and fluorescent in situ hybridization (FISH) to DNA p robes specific for the most probable computer-selected chromosome synd romes. On average, the method allowed the number of necessary DNA prob es to be decreased four times. In the tested patients, supernumerary m arker chromosomes were shown to be derived from chromosomes 2, 9, and 15, and translocations were identified as dic(Y;18) and ins(6;21). Lim ited possibilities of using the method when (1) a chromosome syndrome is not clearly defined in a diagnostic system or (2) phenotypic expres sion of a marker chromosome is not significant are discussed. Presumab ly, the method will allow a reliable estimation of the efficiency of v arious diagnostic systems.