The genetic dissection of complex inheritance in humans remains an exceedingly difficult, if not impossible, task. On the other hand, model organisms have proven to be invaluable for genetic studies due to their clearly defined genetic backgrounds, wide availability of mutant lines, and ease of experimental manipulation. The applications of newly devised analytical strategies and computational tools are widespread and include the characterization of common disorders, analysis of polygenic disorders, and understanding of disease variation. This book guides researchers, who often lack expertise in the underlying genetic basis of complex trait inheritance, through experiments aimed at identifing genes underlying phenotypes of interest.