Figure 5.

Significance of CCTG dumbbell structure. (A) Folding of the last repeat of a CCTG hairpin structure with a 3′-overhanging stem results in a dumbbell structure. (B) Possible dumbbell structures in longer repeats. The dumbbell structure can be formed by the last four repeats with a long 5′-overhang. Alternatively, realignment of the repeat strand can occur, leading to the formation of a dumbbell structure with shorter 5′-overhang but a longer stem. (C) Formation of the dumbbell structure in CCTG repeats stabilizes the slipped hairpin structure and thereby increasing the formation propensity of unusual structure during DNA replication.