Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from generation to generation, while others arise sporadically during an organism's life and cause diseases such as cancer. Researchers are trying to identify and characterize these genetic alterations in the hopes of improving diagnosis and therapeutic options for patients.In this video, we will examine the history of genetic disease research, and explore key questions asked by medical geneticists. Various tools used to identify the genetic basis of diseases are then discussed, including genotyping techniques and genome-wide association studies (GWAS). Finally, several current examples of medical genetics research are presented.