13 Linkage and association with structural relationships

The use of structural equations (path analysis) provides an alternative, equivalent formulation to variance components models. Instead of partitioning the variance, we focus on modeling the underlying random variables themselves through a system of linear, mixed model, regression equations. A few specific examples of genetic path models for linkage and association (linkage disequilibrium) are discussed. This formulation provides a simple yet elegant framework that can continue to be extended to meet the challenges of modeling and dissecting the genetic nature of complex traits in the new century.