CHROMOSOME-STUDIES IN FIRST POLAR BODIES FROM HAMSTER AND HUMAN OOCYTES

Most studies on preconception diagnosis published so far have used pol ymerase chain reaction (PCR) analysis to identify single gene defects. Although fluorescent DNA probes have been used to obtain a partial cy togenetic diagnosis of aneuploidies in first polar bodies without defi ned chromosome structures, the analysis of structural chromosome anoma lies in the interphase nucleus is not adequate. We describe a procedur e to obtain first polar body chromosome complements from hamster and h uman oocytes, In 63.6% (105 of 165) of hamster first polar bodies the chromosome complement showed a defined chromosome morphology and in 94 .1% (16 of 17) of human oocytes fixed after follicular puncture it was possible to obtain high quality, well spread chromosome complements. First polar body chromosomes are fuzzy and shorter than oocyte chromos omes, but fluorescent in-situ hybridization results obtained in human first polar bodies clearly show that it is possible to detect whole ch romosomes, centromeres and unique sequences, including the terminal re gions of small chromosomes, This suggests that in fresh oocytes, DNA l oss resulting from apoptotic chromosome fragmentation has not yet occu rred. Using the procedure described, first polar bodies could be used to analyse the meiotic segregation of maternal structural abnormalitie s and to detect numerical chromosome anomalies in humans.