Segregation of sex chromosomes in human lymphocytes

Centromeric FISH was used to investigate the segregation of ses chromosomes in human lymphocytes. The aim of the study was to evaluate the effects of cell culture, cytokinesis block, age and ses on segregation and to compare the behaviour of the X and Y chromosomes. In uncultured T lymphocytes of fi ve elderly women, the mean frequencies of nuclei hyperdiploid and hypodiplo id for the X chromosome were not significantly affected by culturing the ce lls or hy cytokinesis block. In cultured binucleate lymphocytes of two age groups of men, the X chromosome showed significantly higher mean frequencie s of hyperdiploidy, hypodiploidy and reciprocal gain and loss than the Y ch romosome. Reciprocal gain and loss of the Y chromosome was statistically si gnificantly higher in the older than the younger men. In four women, studie d in the same series, the rates of Y chromosome aneuploidy did not signific antly differ from those obtained in men. In conclusion, malsegregation of t he Y chromosome is common in lymphocytes of both men and women and more fre quent than Y chromosome malsegregation. However, there is no clear ses diff erence for X chromosome reciprocal gain and loss. This would suggest that t he high loss of the X chromosome in women, documented in metaphase studies, is due to micronucleation.