Complex sentence: Certain genes are believed to be responsible for the changes that occurred to the cetacean pelvic structure, such as BMP7, PBX1, PBX2, PRRX1, and PRRX2.
Split into simpler sentences: Certain genes are believed to be responsible for the changes that occurred to the cetacean pelvic structure. Possible gene candidates for modifications made to the cetacean pelvic girdle include BMP7, PBX1, PBX2, PRRX1, and PRRX2.