CYTOGENETIC AND MOLECULAR INVESTIGATIONS OF Y-CHROMOSOME SEQUENCES AND THEIR ROLE IN TURNER-SYNDROME

It has been proposed that all live born females with Turner syndrome c arry a cell line containing two sex chromosomes, which may be present at a low level of mosaicism (Hook & Warburton, 1983; Hassold et al. 19 85; 1988; Connor & Loughlin, 1989). If the second sex chromosome is a Y, these patients are at risk of developing gonadoblastoma. In this st udy, 50 patients found to have a 45,X karyotype by conventional cytoge netic analysis, were screened by the polymerase chain reaction (PCR), for the presence of Y chromosome sequences. Two patients were positive for six of the eight Y chromosome loci tested and additional cytogene tic analysis confirmed the presence of a marker chromosome, in 8 % and 3 % pf cells respectively. Fluorescence in situ hybridization (FISH) was used to confirm that the markers were of Y chromosome origin and h elped to elucidate their structure. In addition, four other patients w ere found to have a Y chromosome by initial routine cytogenetic analys is. :PISH, in conjunction with PCR, elucidated the structure of the Y chromosomes. This study illustrates the value of using a combination o f cytogenetic and molecular techniques, to identify Y chromosome seque nces in Turner syndrome.