Phenotypic distributions indistinguishable from normal distributions are often interpreted as showing the segregation of many genes. Such characters may then be passed over by physiologists and developmental biologists as too complex or otherwise unsuitable for developmental studies. In this paper we present several simple genetic models in which only 2 or 3 loci account for the great majority of the variance, and we show that even with large sample sizes, such distributions may be indistinguishable from normal distributions. The conclusion that a normal distribution must reflect the segregation of a large number of loci is therefore not necessarily justified. Hopefully, problems of the development of quantitative characters which were previously thought to be unapproachable may now be seen to be open to critical examination.
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This work was supported by a grant from the Science Research Council.
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Thoday, J.M., Thompson, J.N. The number of segregating genes implied by continuous variation. Genetica 46, 335–344 (1976). https://doi.org/10.1007/BF00055476
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DOI: https://doi.org/10.1007/BF00055476