CCL3L1 and CCL4L1 chemokine genes are located in a segmental duplication at chromosome 17q12.

Sixteen CC chemokine genes localize to a 2.06-Mb interval at 17q11.2-q12 on genomic contig NT_010799.13. Four of these genes comprise two closely related paralogous pairs: CCL3-CCL3L1 and CCL4-CCL4L1. Members within each pair share 95% sequence identity at both the genomic and the amino acid levels. One BAC clone (AC131056.5) on the contig with substantial internal sequence duplication contains two complete copies of CCL3L1 and CCL4L1 and one truncated copy of CCL3L1, while a partially overlapping clone (AC003976.1) contains one copy each of CCL3 and CCL4. Dot-matrix comparison of the regions of AC131056.5 with those of AC003976.1 containing the four genes reveals 90% sequence similarity over 37 kb. These observations support the idea that the multiple copies of CCL3L1 and CCL4L1 present in a single diploid genome are the result of segmental duplication.