Basic ideas of the prediction method. (a) Schematic illustration of an interrupted ORF (iORF). (b) Readthrough genes can be distinguished from two adjacent genes based on the results of BLAST searches. Boxes denote iORFs, and × indicates the inframe stop codon. Shaded regions represent actual protein-coding regions. If an iORF codes a readthrough protein, BLAST hits from other organisms will cover the inframe stop codon. In contrast, if the iORF consists of two adjacent genes, many hits that do not cover the inframe stop codon will be found.