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 β-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.