Recent developments in molecular and computational methods have made it possible to identify the genetic basis of any biological trait, and have led to spectacular advances in the study of human disease. This book provides an overview of the concepts and methods needed to understand the genetic basis of biological traits, including disease, in humans. Using examples of qualitative and quantitative phenotypes, Professor Weiss shows how genetic variation may be quantified, and how relationships between genotype and phenotype may be inferred. This book will appeal to many biologists and biological anthropologists interested in the genetic basis of biological traits, as well as to epidemiologists, biomedical scientists, human geneticists and molecular biologists.