Asymmetric information transfer during φX174 DNA replication

Abstract

By annealing the single-stranded DNA of φX174 phage with the complementary strand obtained from the replicative form of this phage, heteroduplex RF was prepared with a genetic marker in the viral strand, which is different from that in the complementary strand.

Heteroduplex RF was indistinguishable from native RF in buoyant density in CsCl, in contour length in the electron microscope and in hydroxylamine sensitivity. Heteroduplex RF is infectious to spheroplasts of the appropriate bacterial host. Infected spheroplasts yield a burst of approximately equal quantities of phage of the plus- and minus-strand type and the majority of the spheroplasts produces a single type of phage. This and other evidence indicates that the heteroduplex region is repaired before replication.

The ultraviolet sensitivity of heteroduplex RF DNA is intermediate between that of single- and double-stranded φX DNA suggesting that repair of a heteroduplex region involves the degradation of a large single-strand segment.