Medical genetics / edited by Victor A. McKusick and Robert Claiborne.

Date:
[1973]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Medical genetics / edited by Victor A. McKusick and Robert Claiborne. Source: Wellcome Collection.

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    genetics of man, and the increased information, as well as improved diagnosis and management, which has come out of the application of these techniques to the investigation of disease. Relatively facile methods for examining the chromosomes gave the medical geneticist his organ or system like the cardiologist or endocrinologist. Human chromosomes were visualized as early as 1880 by Walter Flemming (see photo on page XIII ) but the availability of methods for analyzing them in a few drops of blood made a big difference. And, of course, the refined banding tech¬ niques give greater precision to the scrutiny of the chromosomes (see Caspersson and Zech, Chapter Three ). Burgeoning biochemical genetics has often provided surrogates for controlled matings that are, of course, impossible in man. Not only can deductions be made, for example, about the evolution of man from the analysis of protein structure, but conclusions about matters such as mode of inheritance are sometimes possible when only a single patient is avail¬ able (e.g., if both parents have an intermediate level of activity of an enzyme almost completely absent in the patient ). Cell hybridization is what Marcello Siniscalco calls a substitute for sex, another method for getting genetic information which the experimental geneticist obtains through planned matings. We medical geneticists have also been fortunate that the lowly fibro¬ blast has turned out to have such a wide repertory of enzyme activities (see Mellman, Chapter 16). It was not anticipated, by many at least, that fibroblasts cultured from skin biopsies would be almost as useful as liver tissue, for example, in studying diseases such as homocystinuria 100 80 60 « 40 ■M О 20 25 20 15 5 с 10 1915 1925 1935 1945 Year 0 1955 1965 30 25 S 20 < О 15 10 1915 1925 1935 1945 Year 1955 1965 Total Infant Mortality 5 Diarrheal Diseases Infant Mortality Congenital Malformations Infant Mortality Graph at left shows infant deaths in the U.S. from 1916 to 1965. Rapid decline since 1916 in total infant mortality is paralleled by decline in infant mortality from specific infectious diseases, here represented by diarrheal diseases, including dysenteries. During the same period, infant mortality from congenital malformations declined very little. In graph at right, percentage of infant deaths in U.S. from 1910 to 1965 from diarrheal diseases is compared with percentage for congenital malformations. Data are from Dr. Hymie Gordon, Chairman, Department of Medical Genetics, Mayo Clinic (JAMA 217:1215,1971). XIV