Genetic principles in medicine and social science / by Lancelot Hogben.

  • Hogben, Lancelot Thomas, 1895-1975.
Date:
1931
Catalogue details

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

Credit: Genetic principles in medicine and social science / by Lancelot Hogben. Source: Wellcome Collection.

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    equal to the number of mixed pairs. This follows at once from the fact that the probability that an individual will be male (or female) is approximately half. In fact, data collected from different countries show that the number of pairs of like sex is greatly in excess of the TABLE i Sex Incidence of Twins (i) Data for German Empire, 1906-1911 : Male Pairs Female Pairs 49,425 46 ,637 This gives : Like pairs Difference between Like and Mixed Total Like and Mixed Percentage of identical twins (ii) Nichols's data (U.S.A.) : Male Pairs Female Pairs 234,497 219,312 This gives : Like pairs Difference between Like and Mixed Total Like and Mixed Percentage of identical twins (iii) Margaret Cobb's data (U.S.A.): Male Pairs Female Pairs 1,118 1,023 This gives: Like pairs Difference between Like and Mixed Total Like and Mixed Percentage identical twins Mixed Pairs 58,382 96,062 37,680 154,444 24-2 Mixed Pairs 264,098 453,8o9 189,711 717,907 26-4 Mixed Pairs i,i93 2,141 948 3,334 28-4 number of mixed pairs, being generally about twice as great. Some data from the United States and from Germany are presented in Table 1. These show that about 25 per cent, of all twins are produced by some method which is essentially different from the method which ensures a sex ratio of nearly unity in ordinary brothers and sisters.