Variable and Constant Components of Chromosomes

Abstract

A STUDY of isolated chromosomes has shown that they contain desoxyribonucleic acid, histone and another protein of an entirely different character from a histone¹. This protein remains as a microscopic fibre after extraction of desoxyribonucleic acid and histone from the chromosome. The coiled thread that is left after removing desoxyribonucleic acid and histone is called a 'residual chromosome', and the protein of the thread is referred to as the 'residual protein' of the chromosome. Some ribonucleic acid is combined with residual protein. The thread of residual protein is the basis for the thread-like structure of the chromosome. In the isolated chromosomes that were first prepared, those of nucleated erythrocytes of the carp and of calf thymus, the residual protein represented only 4 and 8·5 per cent respectively of the dried mass of the total chromosome, the remainder of the lipid-extracted chromosome being almost entirely nucleohistone.