For a long time, proteins have been considered as the expression forms of DNA or RNA and proteins alone cannot store and transmit biological information. But storing and transmitting biological information are two essential characteristics of genetic materials. With the appearance and development of prion biology, people have known that proteins alone have the ability of storing and transmitting biological information. In some sense, proteins are also genetic materials. It is very necessary to rediscover and reinterpret prion biology in light of this new concept. Common rules of protein-based storage and transmission of biological information and the diversity of their manifestation can be seen by reviewing the history of mammalian prion biology and fungal prion biology and by introducing the latest progress in this field.