1 Cytogenetics of Pregnancy Wastage.- Estimation of Pregnancy Wastage.- Evaluation of the Incidence of Chromosome Abnormalities.- Types of Chromosome Abnormalities.- Animal Model for Meiotic Nondisjunction and Experimentally Induced Monosomy and Trisomy.- Conclusion.- References.- 2 Mutation in Human Populations.- Classes of Mutation.- Mutation Rate Estimates.- Some Special Problems.- Use of Mutation Rates in Genetic Counseling.- Population Kinetics of Mutation.- Assessing the Population Mutation Burden.- Mutation and Evolution.- References.- 3 Genetic Mutations Affecting Human Lipoprotein Metabolism.- General Review.- Mutations in the Pathway of Lipoprotein Metabolism.- Future Directions.- References.- 4 Giucose-6-Phosphate Dehydrogenase.- Glucose-6-Phosphate Dehydrogenase in Evolution.- The G6PD Gene in Humans.- Genetic Variability of Human G6PD.- Expression of G6PD and G6PD Deficiency.- G6PD Polymorphism and Malaria Selection.- Concluding Remarks.- References.- 5 Steroid Sulfatase Deficiency and the Genetics of the Short Arm of the Human X Chromosome.- Sulfated Steroids and their Metabolism.- Steroid Sulfatase (STS).- Steroid Sulfatase Deficiency.- Genetics of Steroid Sulfatase.- Some Genes on the Human X-chromosome Short Arm Are Not Inactivated.- Pairing and Recombination of X and Y Chromosomes.- Conclusion.- References.- Addenda.