The genetic code alone cannot account for all of the information needed for one organism to reproduce, and more attention should be paid to other components and attributes of the fertilised egg, two new papers suggest.
Dr Antony Jose, Associate Professor in cell biology and molecular genetics at the University of Maryland, argues that the genetic code alone cannot account for all of the information needed for one organism to reproduce. Scientists, for example, cannot predict the complex shape of an organ or an animal just from the genetic code.
'DNA cannot be seen as the "blueprint" for life,' Dr Jose said. 'It is at best an overlapping and potentially scrambled list of ingredients that is used differently by different cells at different times.'
Rather than DNA alone, Dr Jose points out that the information for life is actually held in a single cell – a fertilised egg – that goes on to give rise to a whole organism. He proposes that the complex arrangement and interactions of the many different molecules, proteins and structures found in this cell are also crucial for heredity.
'That aspect of heredity, that the arrangement of molecules is similar across generations, is deeply under-appreciated, and it leads to all sorts of misunderstandings of how heredity works,' Dr Jose said.
Dr Jose suggests a framework for heredity, which consists of three properties that are essential for transmitting information from one generation to the next: entities, sensors and properties. Entities include DNA and all other molecules that are found in a cell that are needed to build an organism.
Sensors are specific entities that interact with and respond to other entities or to their environment. Sensors respond to certain properties, such as the arrangement of a molecule, its concentration in the cell or its proximity to another molecule.
Together, entities, sensors and properties enable a living organism to sense or 'know' things about itself and its environment. Some of this knowledge is used along with the genome in every generation to build an organism.
Professor Michael Levin, of the Tufts Centre for Regenerative and Developmental Biology and the Allen Discovery Centre at Tufts University, Massachusetts, who was not involved with either of the published papers, said 'Antony Jose's generalisation of memory and encoding via the entity-sensor-property framework sheds novel insights into evolution and biological complexity and suggests important revisions to existing paradigms in genetics, epigenetics and development.'
This work could have implications for understanding hereditary diseases, which are often studied in terms of the genes which are passed down from one generation to the next. The framework proposed here suggests that looking at the arrangement of other molecules in the cell may also be important.