ABSTRACT
Quantitative genetics is concerned with the inheritance of genetic quantitative traits. Stretches of DNA containing or linked to the genes that underlie a quantitative trait are called quantitative trait loci (QTL) (locus for singular form). The abbreviation QTL is used for both the plural and singular forms. QTL mapping is the study for locating QTL in the genome by using trait and marker genotype data obtained from certain populations. The understanding of the principles of quantitative genetics is crucial for QTL mapping. Unlike qualitative traits which are less influenced by environmental factors and have a deterministic relationship with the affecting genes, quantitative traits are influenced by environmental factors to such an extent that their relationships with the affecting genes are usually masked by the environmental effects. Genetic quantitative traits can only be studied from the aspects of their distributions in certain populations. Therefore, statistical methodology is more crucial in the study of quantitative traits. This chapter is devoted to the principles of quantitative genetics and some general statistical issues on QTL mapping. Section 3.1 covers the distributional nature of genetic quantitative traits. Section 3.2 deals with genetic models of QTL effects and genetic variances of quantitative traits. Section 3.3 tackles the problem of inference on unknown QTL genotypes from marker genotypes. Section 3.4 provides a general discussion on statistical models of quantitative traits. Section 3.5 discusses issues related to QTL mapping data.
