CARD: a drawing tool for RNA secondary structure models.

A graphical editor was developed to create publication-quality representations of RNA secondary structure models. A user-defined model can be gradually assembled from structural elements such as helix segments and loops. The type of structural element to be drawn is chosen from a menu. Its nucleotide sequence has to be entered from the keyboard. Afterwards, drawings can be manipulated by moving, deleting, rotating, copying or changing the structural elements separately. An example of a secondary structure model is given for a complete 18S rRNA molecule.