The ABC of the BX-C: the bithorax complex explained

Abstract
As one of two Drosophila Hox clusters, the bithorax complex (BX-C) is responsible for determining the posterior thorax and each abdominal segment of the fly. Through the dissection of its large cis-regulatory region, biologists have obtained a wealth of knowledge that has informed our understanding of gene expression, chromatin dynamics and gene evolution. This primer attempts to distill and explain our current knowledge about this classic, complex locus.