THE EVALUATION OF GONOSOMAL MOSAICS - LYMPHOCYTE INTERPHASE NUCLEI ANALYZED BY FISH

The reliable evaluation of chromosomal mosaics is still considered to be difficult in clinical diagnosis if aberrant metaphases are only pre sent at low frequencies. Classical cytogenetic findings cannot signifi cantly exclude low mosaic levels, obviously, because of the relatively low number of analyzed metaphases. To study this problem, the number of gonosomes in lymphocyte interphase nuclei was determined by FISH (f luorescence in situ hybridization) application of two satellite DNA pr obes, DXZ1 and DYZ1. The results obtained with this method from lympho cytes of clinically and cytogenetically inconspicuous persons showed a high degree of reliability. The DNA probe yielded correct signals in more than 95% of the analyzed nuclei. Additionally, patients were exam ined who showed cytogenetically confirmed numerical gonosome aberratio ns. These results were compared with those obtained from the control g roup of inconspicuous patients and discussed with respect to the evalu ation of gonosomal mosaics.