Analysis of Tritium-labelled Human Chromosomes and Sex Chromatin

Abstract

IT has been shown^1,2 that differential DNA synthesis in tissue culture may be studied by the incorporation of tritiated thymidine, followed by autoradiography of the labelled chromosomes. Grain counts have been made human chromosomes labelled at the end of DNA synthesis, but the high grain density over the late-replicating X often obliterated morphology³. Asynchronous DNA synthesis has been demonstrated within human interphase nuclei⁴. An area of differential labelling was shown where the sex chromatin body might be expected to be present; but it was reported that the heavy concentration of grains made it difficult to determine whether an underlying body was present.