Dr. Lowry began by briefly reviewing the theory and terminology of genetics as it had developed from the time of Mendel onwards. He introduced the audience to the 46 human chromosomes with a couple of slides showing the complement of a female and a male, pointing out the difference in the appearance of the sex chromosomes; he then went on to discuss the idea of sex-linkage and its significance in some diseases.

Current Study

The central message of his talk was that, at this moment in the history of medicine, there is absolutely no substitute for the detailed and careful family medical history (a concept that should be clear to genealogists) when it comes to assessing the possible risk of a genetic disorder for any given patient.

He showed numerous family trees which showed the occurrence of various disorders through successive generations, and he showed slides of the effects of many of these disorders. He said that it is by the analysis of many family trees in affected families that it has been possible to calculate the tables used by medical geneticists to predict the probability of any given person in an affected family getting the disease in question.

He discussed some difficulties in this procedure that genealogists could readily relate to:

the further back one goes on the family tree the more difficult it is to be sure of the diagnosis in terms that have any meaning for modern physicians
many of the diseases that affect children lead to their death in infancy, leaving the paediatric geneticist and the genealogist with nothing more substantial than "di.": "died in infancy"
genetic disorders which do not show themselves till late in life have been difficult to identify as being of hereditary origin until recently, and even now are easy to overlook

Dr. Lowry showed how useful it has been for geneticists to study closed communities like the Hutterites to study the effects of consanguinity in the transmission of hereditary diseases; he showed some remarkable medical family trees (no names or dates, just squares and circles for males and females) to illustrate this point.

Dialogue

Dr.Lowry's talk was followed by an energetic and prolonged question period, evidence of the widespread interest in this topic on the part of the members of the Society. Perhaps the most telling comment was that he had concentrated on the negative effects of genetic inheritance to the exclusion of the positive manifestations of this wonderful process of Nature; he ruefully conceded the point, saying that doctors, by virtue of their training, have a rather gloomy view of life.