RAPID IDENTIFICATION OF MARKER CHROMOSOMES BY IN-SITU HYBRIDIZATION UNDER DIFFERENT STRINGENCY CONDITIONS

Six metacentric non-satellite chromosome markers and 4 satellite marke rs of unknown origin were discovered by routine cytogenetic analysis. These markers were then investigated by isotopic and nonisotopic (FISH ) in situ hybridization. In order to determine the origin of small mar ker chromosomes, a special protocol involving sequential application o f defined alphoid and 'classical' satellite DNA probes with chromosome specificity was used. In situ hybridization under low stringency cond itions has been performed with DNA probes specific for 4 groups of chr omosomes. After preliminary analysis and determination of the possible origin of these marker chromosomes, DNA probes with high chromosome s pecificity were used under high stringency conditions. Marker chromoso mes were found to be derivatives of chromosomes 7, 9 (3 cases), 13, 14 or 22, 21 (2 cases), X and Y.