Chromosome replication is not a uniform and continuous process. Replication
forks can be slowed down or arrested by DNA secondary structures, specific
protein-DNA complexes, specific DNA-RNA hybrids, or interactions between t
he replication and transcription machineries. Replication arrest has import
ant implications for the topology of replication intermediates and can trig
ger homologous and illegitimate recombination. Thus, replication arrest may
be a key factor in genome instability. Several examples of these phenomena
are reviewed here. (C) 2000 Societe francaise de biochimie et biologie mol
eculaire/Editions scientifiques et medicales Elsevier SAS.