Agarose or polyacrylamide gel electrophoresis is a common technique used to separate nucleic acids (DNA and RNA) according to their molecular weight, which generates images that can be analyzed automatically by a system. The separated DNA fragments of different molecular weights give a series of bands with positions in the gel image corresponding to their molecular weights. Automated image analysis of the gels removes much of the subjectivity of manual interpretation of band positions and sizes. In this paper, an automated system was designed for analyzing DNA bands using image and signal processing techniques. The proposed algorithm consists of four main steps: preprocessing to enhance the image, detecting lanes and bands, identifying band lengths and clustering; in which the similarities of biological samples based on shared bands can be identified. The proposed technique eliminates defects due to noise and double bands in images.