Before revision:  We describe a robust statistical approach to identify conserved loci within genes that are  significantly enriched in slowly translated codons  . Surprisingly, we find that domain boundaries can explain only a small fraction of these conserved loci.
After revision:  We describe a robust statistical approach to identify loci within genes that are significantly enriched in slowly translated codons . Surprisingly, we find that domain boundaries can explain only a small fraction of these conserved loci.