Genetics beyond Mendel. Understanding nontraditional inheritance patterns.

Many medical conditions that clearly have a strong genetic component are not transmitted in a straightforward dominant, recessive, or X-linked pattern. Recent progress in understanding other modes of inheritance, such as imprinting, trinucleotide repeat expansion, mitochondrial inheritance, and mosaicism, has allowed us to solve many of these hereditary puzzles. Such advances have led to improvements in diagnosis and genetic counseling for patients affected with these disorders and should be valuable in development of effective therapies for some of these disorders in the future.