Because only eukaryotic DNA contains intronic regions, this type of gene does not occur in bacteria or archaea.
[1] The human genome contains a relatively high proportion of nested intronic genes.
It is predicted to contain at least 158 functional intronic nested genes, with an additional 212 pseudogenes and three snoRNA genes nested in intronic regions.
[2][1] Genes nested opposite the coding sequences of their host genes are very rare, and have been observed in prokaryotes, and more recently, in yeast (S. cerevisiae) and in Tetrahymena thermophila.
These non-intronic nested genes remain to be identified in metazoan genomes.