A BRIEF HISTORY OF HUMAN CYTOGENETICS

Although there were several workers who had studied human chromosomes before 1956 it is now generally accepted that the beginning of the present science of human cytogenetics was with the publication of Tjio and Levan's paper reporting the correct chromosome number as 46 after studying tissue culture preparations. Soon after this several congenital malformation syndromes who had long been suspected to have a genetic (chromosomal) defect were indeed determined to have aneuploidy e.g. Down (trisomy 21), Turner (45, X), Klinefelter (47, XXY); and some others were newly delineated such as Patau (trisomy 13), Edwards -(trisomy 18), cridu-chat (5p-), Wolf Hirschhorn (4p-). In addition a malignancy, chronic myeloid leukemia, was found to have a small, minute [later called Phl (Philadelphia) -- chromosome. These rapid developments were so impressive to biomedical scientists that several universities around the world founded human genetics departments, divisions, units, or laboratories in their institutions. Basic scientists continued to work on cell lines derived from human tissue and made significant contributions and laid foundations for further growth. Clinician started utilizing developments in this newly founded sub-speciality to help clinical situations which complimented the desire to obtain material for further investigations. Thus, other chromosomal anomalies were described along with translocations, iso-chromosomes, ring chromosomes, inversions (para-and peri-), which were long known to the cytogeneticists who had studied other organisms. We became aware of the role of aneuploidy in pregnancy loss and birth defects in general and obtained some impressions about their population frequency and incidence.