We have published the dynamic extended folding (DEF) method which is a RNA secondary structure prediction approach to simulate the in vivo RNA co-transcriptional folding process In order to verify the reliability of the method we selected the X-ray-determined Tetrahymena group I intron as a sample to construct the framework of its folding secondary structure Our prediction coincides well with the secondary structure predicted by T R. Cech and the X-ray diffraction crystal structure determined by Lehnert V Our results show that the DEF framework structure of Tetrahymena group I intron reflects its function sites in a concise and straightforward manner and the scope of the simulation was expanded (C) 2010 Elsevier Ltd All rights reserved