The expanding repertoire of hereditary information carriers.

A hereditary system that is based on double-helix DNA sequences provides a stable way to store inherited traits and is favored by most life forms on Earth. However, emerging studies on the phenomenon of non-DNA sequence-based inheritance in multiple species, including mammals, urges a rethinking of the nature of hereditary information carriers and the ways in which they encode heritable traits. In this short opinion piece, we discuss how potential hereditary information carriers such as DNA-associated proteins, epigenetic marks, RNAs and organelles could function via distinct and synergistic modes of action in encoding and transmitting ancestral traits, either inherited or acquired from the environment. In particular, we discuss how the 3D structure of chromatin, in addition to its DNA sequence, may represent a higher-order carrier of hereditary information.