Figure 1From: Using hidden Markov models to investigate G-quadruplex motifs in genomic sequencesAn example of G4 structure. (a) Four guanines form hydrogen bonds to their adjacent guanines, resulting in a G-quartet. (b) Several G-quartets are stacked onto each other to form a G-quadruplex (G4) structure. A G4 structure has its sequence as alternate G-runs and loops.Back to article page