IN GENOME Mapping, the entire DNA sequence is mapped in a square whose corners and the associated quadrants are marked A, T, G, C, to represent the four nucleotides that comprise DNA. A nucleotide is represented by a dot in the appropriate quarter or quadrant of the square on the computer screen. Its position within the quadrant is dependent on the previous nucleotide in the sequence.

The point at which the plotting is begun is the centre of the square. The first nucleotide is plotted halfway between the origin and the corner corresponding to the nucleotide, the second nucleotide is plotted midway between the first point and the corner corresponding to the second nucleotide, and so on.

Each quadrant denotes sub-sequences ending with the nucleotide marked at the corner of the quadrant. Each of the four quadrants are further divided into four sub-quadrants, each describing sequences whose last two nucleotides are identical.