THE DISTRIBUTION OF NEWLY SYNTHESIZED DNA IN MITOTIC DIVISION

Abstract

The DNA of the chromosomes of Crepis capillaris was labelled with thymidine-2-C14. The distribution of newly synthesized DNA was established in post-metaphase stages of the division following the period of label incorporation in meristematic root tip cells by quantitative stripping film autoradiography. The analysis of 30 anaphase and telophase cells led to the conclusion that the new DNA is not necessarily equally distributed by the mitotic process and that, therefore, chromosome duplication does not involve the equal partition of parental DNA. This conclusion is not consistent with the hypothesis that every DNA molecule of the chromosome replicates by a mechanism which requires the permanent split of the double helix.