Dot plot (bioinformatics)

These were introduced by Gibbs and McIntyre in 1970[1] and are two-dimensional matrices that have the sequences of the proteins being compared along the vertical and horizontal axes.

For a simple visual representation of the similarity between two sequences, individual cells in the matrix can be shaded black if residues are identical, so that matching sequence segments appear as runs of diagonal lines across the matrix.

Some idea of the similarity of the two sequences can be gleaned from the number and length of matching segments shown in the matrix.

When the residues of both sequences match at the same location on the plot, a dot is drawn at the corresponding position.

These regions are typically found around the diagonal, and may or may not have a square in the middle of the dot plot.