Linkage Analysis of Discrete Traits

INTRODUCTION

Linkage analysis is an important tool for the investigation of the genetic basis of disease traits and has led to the discovery of the single genes underlying such diseases as cystic fibrosis, Duchenne muscular dystrophy, Huntington’s disease, and a wide variety of metabolic disorders. For certain kinds of traits, linkage analysis allows the localization of trait loci on a known genetic map, which can be followed up with fine mapping based on linkage disequilibrium (LD) and ultimate identification of the gene. Successes using this approach have been largely confined to Mendelian monogenic disorders or oligogenic disorders (e.g., breast cancer, Alzheimer’s disease). Complex diseases (e.g., asthma, schizophrenia) involving several to many loci, as well as environmental factors, may require additional strategies to locate risk loci.