Sets of UCRs sharing high sequence similarity are involved in regulation of related genes: the case of Iroquois gene clusters. Four similarly positioned UCRs are located within the two Iroquois gene clusters at chromosomes 5 and 16. Block arrows indicate significant sequence similarity. The arrow width is inversely proportional to the alignment BLASTN E-value. There are additional shorter blocks of similarity between the two three-gene clusters; however, most UCRs have diverged between the two clusters, while still preserved across vertebrates.
Sandelin et al. BMC Genomics 2004 5:99 doi:10.1186/1471-2164-5-99