In vitro induction of uncoiled chromosomes with inhibitors of RNA and protein synthesis.

When inhibitors of cellular DNA, RNA or protein synthesis are added to the growth medium of human lymphoid cells in G2 phase, these agents produce, within narrow ranges of concentrations, G banded or uncoiled chromosomes in the treated metaphase cells. It is suggested that the induced structural alteration is a consequence of an inhibition of the normal chromosome condensation and fusion of bands taking place between prometaphase and metaphase. This inhibition seems to be due to a partial inhibition of G2 phase synthesis of RNA and protein molecules, necessary for normal chromosome condensation in metaphase. It is found that this condensation can be reversed during a resting period after metaphase.