QTL Mapping and Genotypic Distributions for Three and Four Loci

Abstract

Many biologically and economically important traits in higher organisms are quantitative, not qualitative. Some examples of quantitative traits include yield and quality in crops, height, weight and body fat percentage in animals, hypertension and diabetes in humans, and microarray expression data. Genes controlling quantitative traits are called quantitative trait loci (QTL). With the understanding of QTL, it is possible to diagnose human diseases in early stage, breed or genetically engineer superior organisms to obtain desired characteristics, such as increased yield and improved quality, and understand the underlying genetic mechanism of the expression variation in biological studies. In this talk, statistical methods for detecting and locating (mapping) QTL using molecular genetic markers and their key issues related to the genotypic distributions for three and four loci are presented and discussed. The important issues include the study of QTL mapping in various advanced experimental populations, power analysis for separating closely linked QTL and determination of critical thresholds for QTL detection. Simulated and real examples are used for illustration.?