The Sex Chromatin, Or The "Barr Body"

The research during which the sex chromatin was discovered belongs to the category of research known as curiosity-driven research, as opposed to clinical investigation. The former is conducted in the hope of making some discovery that adds to the existing knowledge of basic science and, should it be useful in the clinical setting – as was the case in my research – that is regarded as a welcome bonus. The latter category is directed toward improvement in the diagnosis or treatment of some specific disease. The two types of research are of equal value.

The research during which the sex chromatin was discovered belongs to the category of research known as curiosity-driven research, as opposed to clinical investigation. The former is conducted in the hope of making some discovery that adds to the existing knowledge of basic science and, should it be useful in the clinical setting – as was the case in my research – that is regarded as a welcome bonus. The latter category is directed toward improvement in the diagnosis or treatment of some specific disease. The two types of research are of equal value.

After several years spent on several research projects, all of which were in the field of neurocytology, i.e. the cells of the nervous system, I decided in 1948 to start a project that was designed to learn whether heightened nerve cell activity produced any structural changes in these cells. The experiment required stimulation of a nerve in cats, during which they were anaesthetized. The animals were anaesthetized again when the portion of the brain containing the stimulated cells was removed for microscopic examination. The cats were therefore subjected to no discomfort or pain.

Just after the details of the experiment had been worked out, Ewart G. Bertram applied for a position as a graduate student leading to the Master of Science degree and we worked together on the project. (The work was done in the Department of Anatomy, Faculty of Medicine, University of Western Ontario.) Examination of the sections showed that the nerve cell nuclei contained an especially prominent mass of chromatin, i.e. the particulate matter derived from the chromosomes, these being the nuclear components that bear the genes. However, it was soon found that the special mass of chromatin was present in the cell nuclei of some animals and not of others. Checking the experimental records showed that the mass was present in the nuclei of female cats and absent from those of male cats. It was therefore named the sex chromatin because of the sex difference and this discovery was the beginning of the new science of human cytogenetics, i.e. the relation of chromosome abnormalities to developmental defects. Methods of testing suitable for use in humans were devised and before long, it was shown that numerical or structural abnormalities of the chromosome were responsible for a number of developmental defects. The best known are Turner's syndrome in females, Klinefelter's syndrome in males and Down's syndrome in persons of both sexes. The use of testing for chromosomal abnormalities is of particular interest to paediatricians, endocrinologists and psychiatrists, especially those who are involved with the mentally retarded.

It is worth mentioning that soon after the results of our work were published in medical journals, the work was taken up in numerous universities, especially in other medical centres in Canada, and the United States, Great Britain and France. The research in my laboratory was made possible almost entirely by grants from the Medical Research Council of Canada.