Figure 4.

(A) Two dimers of the cyclic octamer arranged so that the thymine rings of T3 and T17 of one are in van der Waals contact with those of T7 and T13 of the other. For clarity, only backbone atoms are shown as spheres. (B) Side view showing only the nearer molecule of each dimer. Putative new phosphodiester bonds between O3′ of T2 and P of T3 are represented as dashed lines. (C) Proposed course of recombination according to this mechanism between two duplexes containing the self-complementary sequence d(GCATGC).