The gene for Ornithine transcarbamylase (OTC) is located on the short arm of the X chromosome at Xp21.1, and spans approximately 160 kb of sequence. The GenBank Reference Sequence for human OTC mRNA is NM_000531.4.
A schematic of the X chromosome with the location of OTC and several adjacent genes that have been associated with disease.

There are 10 exons that make up the OTC gene. Three of the exon junctions result in split codons as shown below


In the clinical lab, we use a "cheat sheet" to read each exon and determine mutations.