New Chromosomal Syndromes

The field of human cytogenetics has changed considerably since 1891 when Hansemann studied chromosomes in human cells and attempted to assign a chromosome number to them.¹ The first important discovery was made in 1949 by Barr and Bertram when they observed the sex chromatin body, a small, darkly staining chromatin mass present in the interphase nuclei of females² (Fig 1, left). This discovery later made possible the presumptive diagnosis of Turner and Klinefelter syndromes by the simple analysis of a buccal smear. After 1956, when Tjio and Levan together developed a simple technique that made possible the study of human chromosomes,³ the field progressed rapidly. During the ensuing five years, the causes of trisomy 13, 18, and 21 syndromes; Turner syndrome, and Klinefelter syndrome were established. The next five years saw the application of autoradiography for better identification of chromosomes and the delineation of more subtle chromosome