ADVANCES IN GENETICS increases its focus on modern human genetics and its relation to medicine with the merger of this long-standing serial with Molecular Genetic Medicine. This merger affirms the Academic Press commitment to publish important reviews of the broadest interest to geneticists and their colleagues in affiliated disciplines. Genetics, the science of heredity, lies at the heart of biology, and many diseases are impacted by an individuals genetic make-up. The field of genetics is rapidly evolving and new medical break-throughs are occurring as a result of advances in knowledge of genetics. Advances in Genetics continually publishes important reviews of the broadest interest to geneticists and their colleagues in affiliated disciplines. This volume of ADVANCES IN GENETICS contains the following articles: Targeted Expression of Tetanus Toxin; Germ-line Transformants Spreading Out to Many Insect Species; Genes Mediating Sex-Specific Behaviors in _Drosophila_; and Evolutionary Analyses of Genes and Their Functional Implications.