Schematic illustration of the relationship between query and reference sequences.

<p>A query sequence (filled circle) and reference sequences similar to the query sequence (open circle) are shown. The range of nucleotide variation of the genus (gray area) is shown with reference sequences of species and in the genus (A and B, respectively). Distance between the sequences represents genetic distance in the schematic two-dimensional space. (a) A case in which our new criterion works well. The query falls within the nucleotide variation range of genus . (b) A case in which our new criterion might produce misidentification. Because the genetic distance between a query sequence and the sequence similar to it (A) is smaller than the genetic distance between sequence A and sequence B, the query sequence will be assigned to the genus under our new criterion.