Genetics for the clinician / C.A. Clarke.

  • Clarke, Cyril A. (Cyril Astley)
Date:
1964
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Genetics for the clinician / C.A. Clarke. Source: Wellcome Collection.

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    ELEMENTARY STATISTICS 315 few individuals, and demonstrated by a deep valley between the humps. Thus, in a European population (as is explained fully on p. 217) this situa¬ tion obtains in the inherited capacity to taste phenylthiocarbamide. About 70 per cent of people can taste the compound whereas about 30 per cent are unable to do so. A small percentage of people fall in the antimode or intermediate group and are difficult to classify. Bimodal Distribution. Distribution of PTC taste response in 265 normal individuals (Kitchin etat 1959) Strong solution »-Weak solution Figure 20.9 Fig. 20.9 shows the distribution of taster status in a group of 265 normal people—hospital nurses and university students. Starting from a high dilution and working downwards towards stronger solutions the subject tastes a few millihtres of the solutions until a definite taste is perceived. Having found an approximate threshold (say No. 10), the subject is then given eight glasses—four containing the PTC solution at the concentration shown in the prehminary test (No. 10), and four con¬ taining water. The eight glasses are arranged at random and the subject is asked to separate the two groups. If this is done correctly a further eight-