What do "mad cows", people with neurodegenerative diseases and an unusual type of inheritance in yeast have in common? They are all experiencing the consequences of misfolded proteins.  When misfolded proteins persist the consequences can be deadly, leading to such devastating diseases as Alzheimer’s Disease. And, when passed from one individual to another, misfolded proteins produce infectious neurodegenerative diseases, like Mad Cow disease. Studies on a similar process in yeast cells have revealed beyond a reasonable doubt, a new protein-based mechanism of heredity in this organism. The process of protein misfolding in yeast provides an excellent model for understanding misfolded proteins in humans and accelerates the rate at which we can probe the nature of disease processes and test new therapeutic strategies. From the Series:Distinguished Leaders in Science