[Theory for identification of disease-related genes using genetic polymorphisms]

There are 2 different approaches to search for disease-related genes: a knowledge-based approach using the functions of molecules, and a statistics-based approach using polymorphisms. In the latter approach, researchers search for disease-related sequences or test the association between the sequence and the disease using statistics. Statistical methods are classified into 2 subdivisions: a linkage-based method and a linkage-disequilibrium-based method. For the former method, Mendel's laws are directly applied and the samples should be families, while for the latter method, Mendel's laws are only indirectly applied and the samples do not have to be families. As an example of the former method, an algorithm of linkage analysis based on the Lander-Green algorithm in which hidden Markov model is used is explained herein. As an example of the latter method, a program inferring haplotype frequencies and diplotype configurations of individuals is explained.