Functional significance of the differences in size between homologous chromosomes

Abstract

In comparing cultures of human lymphocytes stimulated with Tuberculin and with phytohemaglutin, it has been observed that the frequency and distribution of the differences in size between homologous chromosomes vary significantly between the two types of culture. This observation, together with those carried out on tetraploid cells and with endoreduplication, permits us to assert that the differences in size between ho­mologues cannot be explained solely as technical contrivances, but must have a functional significance. The authors suggest that such differences may be due to the existence of segments with distinct states of condensation, and consequently of activity, in the two homolo­gous chromosomes, varying between some cells and others in relation to the functional state of the genoma in the same.