What is the difference between Xpro, SEGE and IGD?
Several databases such as the Xpro contain a division of intronless coding sequences but there is only one database, called SEGE, entirely devoted to intronless genes. However, all these databases seem to consider intronless coding sequences (CDS) i.e. genes having their coding sequences contained in a single exon, rather than genuine intronless genes. In fact, genes with intronless CDS might have one, two or more non-coding exons (see figure below). This means that a variable number of the entries of Xpro and SEGE databases may be multi-exonic.
