Search for Linkage between Genes determining a Vitamin Requirement

Abstract

WHETHER genes are distributed at random between and along the chromosomes, or show some systematic arrangement related to their function in the biochemistry and morphogenesis of the organism, has long been a crucial problem in genetics^1–4. The location of genes in relation to their detectable effects in organisms as varied as maize, Drosophila, the mouse, man and Neurospora suggests that “if such a distribution [non-random] exists it does not leap to the eye”⁵. However, there have been enough exceptions to suggest that the problem is by no means settled. Cases are known of closely linked genes having similar effects on the phenotype, for example, ‘lozenge’⁶ and ‘bithorax’¹ in Drosophila, ‘brachyury’ in the mouse⁷, perhaps Rh in man⁸ and recently nicotinic acid requirement in Neurospora⁹. In all these cases linkage was not expected on any reasonable working hypothesis and was discovered accidentally.