Morphogenetic studies of the rabbit. XXXVII. Genome, gradient growth pattern and malformation.

Abstract

AbstractThe metameric organization of the skeleton provides a cartograph of reference points and a unique opportunity for analysis of the polygenic background of the genome and its potentialities for maintaining normality or inducing spontaneous malformation. The position of the vertebral borders indicates the relative size of the thoracic and lumbar regions or gradients. Analysis of homeotic variations in progeny from matings of specific parental vertebral formulae has provided a critical evaluation of the relative effects of gene Da with that of the residual genomes of races DA and IIIDa. Significant differences in shift of the vertebral borders have revealed the segregation of several modifying influences interacting at each border in each strain and with Da when it is present. The segregation patterns demonstrate the polygenic background of these variations and the interaction effects of DA and IIIDa genomes which respectively enhance or suppress the retardation effects of Da upon thoracic and lumbar gradients. Discussion of these observations with reference to convergence of broadly related concepts in the literature leads to the conclusion that many species or strain differences in experimental response, spontaneous malformations and polymorphisms may arise by similar interactions from residual heterozygosity of minor modifying genes within the genome. The importance of a more intensive scrutiny of the genome with reference to spontaneous and experimentally induced malformations is indicated.