1984 年 29 巻 6 号 p. 597-606
The term of 37 years, from 1925 to 1961, could be divided into five periods. The first corresponds to one with a stable and high birth rate, the second to that of Japan-China War, the third to that of World War II, the fourth to that of postwar with its rapid drop in birth rate and the fifth to that with a low birth rate since then. This classification of period shows the change of historical conditions of Japan.
The materials for the test of homogeneity were prepared from random sample from the cards of the registered donors in Shimane, Yamaguchi, Akita and Iwate Prefectures and Bernstein's method was applied to estimate the gene frequencies (p: gene of A, q: gene of B, r: gene of O).
The results of the test of homogeneity between each period could be expressed as follows: in Shimane Prefecture; q in the third period decreased, in Akita Prefecture; q in the third peroid decreased, in Yamaguchi Prefecture; p in the fourth period increased and in Iwate Prefecture, q in the latter half of the fifth period decreased.
The effect of hybridisation, areal biased donation, immigration and inbreeding must be considered as possible factors in the change of gene frequency.
There is very little hybridisation in Japan and is not relevant here.
Areal biased donation which means an increase or a decrease of coming donors from particular districts was demonstrated in the survey of Shimane blood center, and in the population size of the blood center level this biased donation shows no significant change of gene frequency.
An assumption of 4% immigration, from Akita to Shimane Prefecture, revealed no change of gene frequency, but when immigration amounted to 10% in two or more years the test verified that there is a significant change in the distribution of gene frequency. But such an excessive immigration is not the real condition in prefectures of country-side.
If there is an effect of inbreeding, there must be a significant difference of p2, q2 and r2 between the first period and the fifth period, since the fifth period corresponds to the second generation of the first period. But the results of these computations were not significant in any of the four prefectures. The change of previously mentioned social and historical conditions have led to decrease of the number of birth, the fractionising of population, the temporary isolation of inhabitans and then subsequent relaease of fractionising and isolation. The consequence of these changes is the so called “bottle-neck effect”.
In countries of the world where a high frequency of hybridisation takes place the results such as mentioned here would be difficult to obtain.