DNA Replication: The Rolling Circle Model
This extract was created in the absence of an abstract.
Excerpt
Why do DNA circles occur? The rolling circle model for DNA replication suggests that DNA must be circular in order to be copied completely; the basic mode of reproducing an entire genome is to copy it from a circular template, using the circularity in an intrinsic way to guarantee that all of the genetic information is preserved. The guarantee is enforced by copying always more than one full genome's worth: copying the circle plus a bit. The model uses an asymmetric mode of replication and thus can employ the E. coli DNA polymerase or analogous enzymes. The synthesis begins by opening one strand of the original circle at a specific point. We imagine that the positive strand is opened, that the newly exposed 5′ end is attached to the ‘membrane,’ and that a new copy of this strand is synthesized by chain elongation of the 3′ end of the old...
