rolling circle replication
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rolling circle replication or sigma (r) replicationa mode of REPLICATION for some double-stranded circular DNA (or RNA) molecules, such as certain BACTERIOPHAGE GENOMES. A NICK is first introduced into one of the strands of the double-stranded molecule. The other strand remains closed and serves as a TEMPLATE for DNA synthesis. The circular structure ‘rolls’ as synthesis proceeds, and the open strand is gradually displaced, creating a tail. The tail also serves as a template for DNA synthesis. As rolling circle replication continues unabated a CONCATEMER may form from the tail, where many turns of the circle occur before the tail is cut to generate a monomer. Since the molecular structure created during the replication process resembles the Greek letter sigma, it is also referred to as replication. This is the way certain VIRUSES achieve replication of the genome.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005