This volume of ADVANCES IN GENETICS furthers the serial's goal of presenting topics of interest to both human and molecular geneticists. Topics of interest in this volume include: Expression patterns of regulatory genes and the role they play in development Hereditary ataxias and specific disease states where the genetic defect has been identified _Minute_ genes, their mutations, and their molecular function in _Drosophila_ The genetics and molecular biology of rhythm mutants and clock molecules Double strand breaks in DNA and their repair mechanisms Key Features * Expression patterns of regulatory genes and the role they play in development * Hereditary ataxias and specific disease states where the genetic defect has been identified * _Minute_ genes, their mutations, and their molecular function in _Drosophila_ * The genetics and molecular biology of rhythm mutants and clock molecules * Double-strand breaks in DNA and their repair mechanisms and lack of repair mechanisms resulting in human disorders