Authors' contributions: JV contributed to writing the article, study concept and design, acquisition of data, analysis, and interpretation of data. SN contributed to analysis and interpretation of data and critical revision of the article for intellectual content.

Carbamyl Phosphate Synthetase I (CPSI) (EC 6.3.4.16) is a highly conserved mitochondrial enzyme catalyzing the first committed step of waste nitrogen metabolism in the urea cycle. Using FISH for physical mapping and CEPH families for linkage analysis, we mapped the CPSI gene (CPS1) to 2q34→q35, reassigning it from 2p where it was originally mapped.