It has been observed by many researchers that the protein-coding regions of DNA sequences exhibit a period-3 behavior due to codon structure. Identification of the period-3 regions helps in predicting the gene locations, and in fact, allows the prediction of specific exons within the genes of eucaryotic cells. Traditionally these regions are identified with the help of techniques such as the windowed DFT. In this paper we consider the use of efficient digital filters for the same purpose. The filters can be designed not only to extract the period-3 component, but at the same time effectively eliminate the background 1/f spectrum exhibited by nearly all DNA sequences.
