Clinical genetics / edited by Arnold Sorsby.

Date:
1953
Catalogue details

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

Credit: Clinical genetics / edited by Arnold Sorsby. Source: Wellcome Collection.

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    OTHER TRAITS of one cerebral hemisphere over the other, and preference for use of the right or left eye and the right or left foot comes from the same source. There are many individuals in whom the preferences are mixed, however; a person may be right- eyed, left-handed and right-footed. In these circumstances it is not surprising that the genetics of handedness is confused, and hkely to remain so until its physiological basis is better understood. Finger and palm patterns The patterns of the papillary ridges on the fingers and palm are genetically determined, and indeed used as one of the prime indications of monozygosity in twins. The mode of their inheritance is not clear, however, beyond the fact of being multifactorial. The finger patterns are classified in whorls, loops, and arches, but intermediate forms are numerous, and it appears that the patterns depend on genes controlHng skin thickness and the general shape and structure of the hand as well as on genes concerned with the growth of the ridges themselves. Electroencephalographic pattern Under standard conditions of rest and relaxation individuals have a characteristic electroencephalographic pattern which does not vary much from day to day. Studies on monozygotic and dizygotic twins by Lennox, Gibbs and Gibbs (1945) provide evidence that a great deal of the E.E.G. differences between individuals are hereditarily determined, though not in a simple way. They compare the E.E.G. record to the facial features in complexity. Using apparent identity of E.E.G. record as a test of monozygosity, they were able to pick out the two sorts of twins with only 4 per cent wrong and 11 per cent doubtful in 55 monozygous pairs and 5 per cent wrong and none doubtful in dizygous pairs. Superficial veins of mammary region The pattern of the superficial veins draining the mammary region of the chest can be visualized by infra-red photography, and appears to fall into one of two distinct classes, transverse or longitudinal. In the former the veins travel across the chest and drain into the axillary region, and in the latter they travel upwards along the chest and drain into the clavicular area. Spuhler (1951) has reported that in American Indians (Ramah Navahos) about 70 per cent have the transverse pattern, and quotes a corresponding figure of about 90 per cent for American whites. There seems to be no sex difference in incidence. Spuhler's figures agree with the hypothesis that the pattern is controlled by a single autosomal pair of genes with full penetrance, the transverse pattern being given by the heterozygote as well as by one of the homozygotes. In the same paper Spuhler discusses the less well-defined inheritance of the peroneus tertius muscle and the number of vallate papillae on the tongue. Tests of physiological function There have been very few studies on the genetics of physiological function in the human, despite the obvious importance they would have in elucidating differences in morphology and behaviour. Jost and Sontag (1944) have reported a study from the Fels Research Institute in which heart rate, respiration rate, 173