, Volume 51, Issue 1, pp 95-114

Genetical studies on the skeleton of the mouse

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Summary

  1. The genetical behaviour of a number of skeletal characters which differentiate the pure lines CBA and C57BL is described in crosses between these two strains, between C57BL and A, and in some subsidiary experiments.

  2. The results indicate that the entities investigated are ‘quasi-continuous’ characters in the sense that the underlying genetic basis is a continuous variable (generally not yet identified) with multiple factor inheritance which is divided by a physiological threshold into normal and abnormal animals; the abnormality is usually itself capable of graded expression.

  3. The peculiar genetical properties of quasi-continuous characters are regarded as partly due to the fact that a continuous distribution may occupy any position in relation to a physiological threshold; and partly that they share with ordinary continuous variables the multiple gene basis and the sensitivity to influences of the environment, both prenatal and post-natal.

  4. It is suggested that additiveness of gene effects and sensitivity to the environment may trace back to the common cause that the so-called multiple genes of quantitative genetics are in fact remote gene effects. It is pointed out that arbitrarily chosen parameters will generally be influenced by genes only indirectly; and as every measurement involves a choice and is thus arbitrary, the multiple gene inheritance generally encountered in quantitative genetics may be due to the arbitrary choice of parameters rather than to inherent causes.

(With Three Text-figures)