Historical Perspectives

Abstract

Fifty years ago, Professor Paul Polani and colleagues described young women who had Turner syndrome and were found to have apparently male “chromosomal sex.” (1) At that time, the generally accepted number of chromosomes in humans was 48. Five years earlier, Barr and Bertram described the presence of a prominent mass of chromatin lying close to the nucleolar membrane in neurons of some female cats. (2) This “sex-chromatin” was not found in the males. These “Barr bodies” later were detected in cells grown from skin biopsies. (3) Then, in 1956, Tjio and Levan reported that the number of diploid chromosomes was 46, (4) which rapidly was confirmed by others. (5) From this ripple, a wave soon developed. Three years later, the first association of a clinical syndrome with an abnormal number of chromosomes was reported from France (6) and quickly confirmed in Scotland. (7) This was the association of Down syndrome (mongolism) with an extra chromosome number 21 (trisomy 21), although this was called chromosome number 22 at the time. Not long afterward, translocation was noted in a girl who had Down syndrome born to a 21-year-old mother, (8) and translocation was described as a cause of familial mongolism. (9) Other trisomies soon were described. (10)(11) Based on the realization that the number of sex-chromatin bodies was one less than the number of X chromosomes present, the chromosomes of women who had Turner syndrome and appeared to be chromosomally “male” were investigated. They were found to have 45 chromosomes, with the sex chromosomes being XO. (12) Many of these exciting chromosomal discoveries were made by Professor Polani and his colleagues. Elsewhere, Professor Polani (now 90 years old) has described in detail the origins and evolution of clinical cytogenetics. (13) In this issue of NeoReviews , …