Comparison of (A) a hypothetical gene on Chromosome 22 (29720 EID identifier) at the top of the figure and (B) a ABC-transporter-like gene from Chromosome 1 (1786 EID identifier) shown at the bottom. The coding parts of the exons are shown as boxes, introns as thick lines, and noncoding regions as thin lines. Start and stop codons are shown as ATG and ^*, respectively. BLAST comparison revealed 97% identity between the second phase 2 intron of the ABC-transporter and the first phase 1 intron of the hypothetical protein. Manual examination of these genes showed that nucleotide identity (95% overall) extends over the entire shown region and beyond, extending at least 8000 nt. Despite the fact that the nucleotide sequences of exons 2 and 3 of the ABC-transporter are homologous to exons 1 and 2 of the hypothetical gene, they code nonsimilar polypeptides because they are translated in different frames shifted by 1 nt.