Epidemiology and genetics are two distinct disciplines that converge into a new field of human science. Genetic epidemiology is a broad term used for the study of genetics and inheritance of disease. Genetic epidemiology is a science that deals with etiology, distribution, and control of disease in groups of relatives, as well as inherited causes of diseases in populations. In particular, genetic epidemiology is a discipline which focuses on the role of genetic factors and their interaction with environmental factors in the occurrence of disease. Genetic epidemiology can proceed with little or no understanding of the genetic mechanisms involved in disease. Major analytical components of the discipline can be identified in the concept of the qualitative trait,i.e., the gene as an unit of transmission across generations, and in the quantitative trait, i.e., the possible inheritance of a trait such as measurable...