Factors Affecting Vertebral Variation in Mice

Abstract

ABSTRACT As a test for genetic differences within that part of the C3H inbred strain of mice which has predominantly 5 lumbar vertebrae, males from each of three C3H(5) colonies were crossed to C57BL females. The F 1 offspring differed in vertebral type according to paternal origin, showing that genetic divergences between colonies and substrains have occurred within that section of the C3H strain which has predominantly 5 lumbar vertebrae. These matings also gave further evidence, in the form of significant hetero-geneity between litters, that vertebral type is in part determined by a fluctuating variable of the mother’s physiological state. We have summarized published data on the variation of the number of lumbar vertebrae in mice in the C3H and C57BL inbred strains and their F1 and F2 hybrids. On certain assumptions we find that the inbreds are about twice as variable as the F1 hybrids.