The pairing probabilities plot, also called a dot plot, is a visual representation of the likelihood that any two bases in a sequence will form a base pair.
Points on the plot represent individual base pairs. The bottom left triangle shows only the base pairs that are present in the target structure. The top right triangle shows the base pairs predicted to form. The darker the point, the more likely the pair is to form. An ideal dot plot is a mirror image, reflected along the diagonal.
The dot plot can provide insight into the range of structures that a sequence could potentially form. Stacks appear as diagonal rows of dots. In an ideal dot plot, the bottom left triangle (desired pairings) and top right triangle (predicted pairings) are identical.
A "good" dot plot does not guarantee successful folding. The calculations used to predict pairing probabilities are based on the free energy calculated for an RNA. Poor designs with extremely low in free energy, such as christmas trees, may appear to have "good" dot plots. Extremely messy dot plots, however, do reliably predict low synthesis scores.
Example 1: A Moderately "Messy" Dot PlotEditIn this dot plot, the bottom right and top left triangles differ considerably. This suggests that the RNA in question can form multiple structures that are close in energy.