The bithorax gene complex (BX-C) in Drosophila is a model system for studying how genes regulate growth and development. The complex spans over 300 Kb of DNA and comprises a series of protein-coding and cis-acting genetic units that act as master regulators of the growth and development of much of the thorax and abdomen of the organism. The broad objectives are (1) to determine how the individual genetic units of the complex are themselves regulated such that they become expressed along the body axis of the organism in an order that exactly parallels their order in the chromosomes; and (2) to determine the reason that the genes of the complex have remained tightly linked over the immense evolutionary time period since the cluster is believed to have arisen. The specific goals are: (1) to saturate in so far as practical cis-regulatory regions of the BX-C with chromosomal breakpoints ; (2) to characterize such breakpoints genetically, cytologically and morphologically in order to determine the specific subfunctions controlled by each cis-regulatory region; (3) to derive in so far as practical a complete series of deletions of variable length within the BX-C; and (4) to test the hypothesis that the BX-C and other similar types of gene clusters have remained intact over long evolutionary time periods as the result of a sharing of cis-regulatory regions between adjacent structural genes of the clusters. Health relatedness: Mutations within cognates of the BX-C genes in human beings may be at the basis of many types of congenital malformations and may also be responsible for many types of tumors.
