Figure 1.

Resolution of Holliday junctions in early replication intermediates can generate a number of different products. (i) The ERI. (ii) An ERI in which one end (the origin-proximal end) of the nascent DNA has regressed. This could happen with equal probability at the other end as well. (iii) Cleavage of the Holliday junction in ii generates an α structure. (iv) An ERI in which both ends of the nascent DNA have regressed. Because resolution of each Holliday junction can occur in one of two ways, two sets of products are generated: a nicked circle (form II) and a short duplex DNA corresponding to the distance on the replicated portion of the template that is between the sites of resolution (which will vary depending on the amount of nascent DNA that has regressed) (v); and a linear molecule that is longer than the original template by the distance on the template that is between the sites of resolution (vi). Red, the leading-strand template; blue, the lagging-strand template; green, nascent DNA.