Based on a 3-D graphical representation of DNA primary sequences by Li and Wang [C. Li, J. Wang, Comb. Chem. High Throughput Screen. 7 (2004) 23], we outline one approach to arrive at quantification of similarities by constructing a three-component vector whose components are the geometrical center and a four-component vector consisting of the graph radius associated with DNA curves. The examination of similarities/dissimilarities among the coding sequences of the first exon of beta-globin gene of 11 species illustrates the utility of the approach. Our method has the advantage of greatly reducing the computational complexity, and shows the multiformity of analysis of similarities. (c) 2005 Elsevier B.V. All rights reserved.