Heredity in ophthalmology / Jules François.

  • François, J. (Jules)
Date:
1961
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity in ophthalmology / Jules François. Source: Wellcome Collection.

    74/750 (page 70)
    70 GENERAL GENETICS cally by a symmetrical bell-shaped curve. An example concerning height is given in Fig. 56. A company of 175 soldiers was divided into 14 groups according to height, which varied between 1.5 and 1.85 M. Most phenotypes are grouped around the middle values from 1.625 to 1.775 M. Only 32 men out of 175 were below or above that. It has not been possible so far to demonstrate with certainty the polymeric inheritance of pathologic conditions in man which should then exhibit a whole series of intermediate types. In a general way, therefore, one can say that there is no intermediate type between the normal and pathologic types, for example, between a normal retina and one affected by pigmentary degeneration, but there is one exception in ophthalmology—ametropia. Between a very pronounced myopia and a very pronounced hypermetropia, one can find all the intermediate ametropias. One could thus postulate a plurifactorial mechanism on which factors such as the axial length of the eyeball, the refraction of the cornea, the refraction of the lens, the depth of the anterior chamber, etc., depend. Can we conclude then that polymeric inheritance plays no role in human pathology? Not at all. The following facts, in so far as they have genetic appli¬ cation, seem to depend upon multifactorial mechanisms. 1. When several individuals are attacked by the same microbe, differences in susceptibility or resistance between them become obvious. 2. When several members of a single family who share part of their genes are attacked by the same disease, whether infectious or metabolic, they react generally in a similar fashion, and they also show the same predisposition to that disease.