Distribution of Nucleic Acid in the Cell

Abstract

MR. CALLAN, in his defence of the established position of nucleic acid in the nucleus, has completely missed the main significance of our results. Whatever the function of nucleic acid may be, and we have no doubt that it is an important one, and however it may be distributed in the nucleus, its position as the central figure of the chromosomes has disappeared with the discovery of chromosomin. This was the point which we set out to establish in our former article, and we claim that the facts which we have adduced both there and elsewhere¹ give incontrovertible proof of our contention. In dividing cells, chromosomin is quantitatively the major constituent of the nucleus, it is concentrated wholly in the chromosomes, and its presence there supplies for the chromosome theory of heredity a basis which Mirsky², and no doubt many others, have recognized could not be filled by either nucleic acid or histone, the only constituents of nuclei hitherto known. We regard chromosomin, in fact, as the chemical basis of inheritance. By this we mean that the type of organism into which a zygote will develop will primarily depend upon the composition of the chromosomin contained in the gametes from which it was formed. We recognize, of course, that it must, within limits, be organized in a definite manner in the chromosomes. Variations within these permissible limits would, no doubt, account for the existence of different hereditary characters, usually ascribed to genes, within a species or race.