Biopolymers and cell. 1985. Volume 1. № 5. 227 - 233

N. A. Liapunova

REPLICON ORGANIZATION OF THE GENOME OF HIGHER ORGANISMS: CRITICAL ANALYSIS OF RACTS AND HYPOTHESIS

Summary

    The size measurement of replication units (replicons) by the method of DNA-fibre auto-radiography is critically analyzed. It is shown that the conception of «clusters of small •replicons (30-50 u.m)» is untenable. The model for organization of eucaryotic chromo¬some replication is suggested. This model is based on the known temporal order of replication of the functional chromosome blocks (G~->G+-»-C) and on the existence of large replicons (100-200 u.m and more) being approximately equal to DNA fragments in one average-size functional block (300 u,m). The model is also based on the assumption Wiat the replicon initiations are grouped at three discrete short time intervals disrupted by prolonged time intervals during which only DNA chain elongation and replicon termination occur. The model explains uneven DNA synthesis during the S-period and facilitates a search of mechanisms for genetic control of the replication time sequence of different genome parts.