1 Introduction DNA (deoxyribonucleic acid) that carries the genetic information used in the growth, development, is a molecule many viruses, and reproduction of all known living organisms and (T): Guanin (G) and has four building blocks called (A), as a code Cytosine All information in the DNA is stored made up of these four chemical bases. the Sub-strings of a DNA sequence hav length k are called k For Figure 1 k-mers of length 4 (k of the sequence shown in In this example w refers to step size with which the sliding window is moved. With w the window moves 1 letter to the right at each step, so that the first k-mer starts at position 1 and the second starts at position 2 and so on. The usage data over the "GATTACA" in this case is [(GA where each couple represents a k-mer (k 4) and its frequency of occurrence in this sequence. When w 2, the first k-mer starts at position 1, the second k-mer starts at position 3, the third position starts at 5 but since there are fewer than 4 nuclotides left, the count stops. The usage data for this case is IGATT,1), (TTAC,1) G A T T A C A G A T T T A C A C A Figure 1: Example of k-mers where k 4 and 1