ADVANCES IN GENETICS has established itself as an outstanding vehicle for the dissemination of research results in genetics. Once again, authoritative papers are presented here, beginning with a review by Rai and Black highlighting the salient features of mosquito genomes and their evolution. The recent progress which has been made by the cloning and characterization of two cooperating partners of the Neurospora blue light signal transduction chain is presented by Linden, Balario, Arpaia, and Macino. The emergence of the concept of X-linked mental retardation (XLMR) is discussed by Neri and Chiurazzi, as well as epidemiologic data and XLMR gene updates. In chapter 4, Mahato, Smith, and Rolland provide insights into the potentials of plasmid-based gene therapy and critical evaluation of gene delivery sciences and clinical applications of gene medicines. Kathleen Triman completes the volume with an outline of the genetic strategies designed to improve our understanding of the structure and function of 23S ribosomal RNA in _E. coli_.