For biologist Antony Jose, from the University of Maryland, USA, heredity is the result of three components: entities, sensors, and properties.
A consensus on heredity is that all information passed from one generation to the next is stored in an organism’s DNA. But new research conducted by biologist Antony Jose, from the University of Maryland in the United States, suggests that this is not always true.
In two new articles published last Wednesday (22), in the Journal of the Royal Society Interface and BioEssays, Jose argues that DNA is like the “list of ingredients” needed to keep the organism alive. In the meantime, the “way of doing” (i.e., executing these instructions) is left to the molecules that regulate the DNA in each cell.
Jose’s argument is that, by focusing on DNA, scientists are neglecting other important aspects in the study and treatment of inherited diseases. Besides, he believes that current studies about evolution focus too much on the function of genetic material.
“DNA cannot be seen as the ‘blueprint’ for life,” the scientist said in a statement. “It is at best an overlapping and potentially scrambled list of ingredients that is used differently by different cells at different times.”
For example, the gene for eye color exists in every cell in the body, but the process that produces the protein responsible for the color occurs only during a specific stage of development and only in the cells that make up the colored part of the eye – and that information is not stored in DNA. In addition, genetic material is not responsible for dictating some aspects of animals’ eyes – this is determined by something that is outside of DNA.
A new theory
With this in mind, Jose argues that those aspects of development, which allow a fertilized egg to grow from a single cell and become a complex organism, must be seen as an integral part of heredity. For the specialist, heredity works as a complex, networked information system, in which all the regulatory molecules that help the cell to function can store information.
Jose proposes that the instructions not encoded in the DNA are in the arrangement of the molecules present inside the cells and in the way they interact with each other – and these aspects are transmitted to our descendants. The researcher argues that inheritance is the result of three components: entities, sensors and properties.
Entities include the genome and all other molecules within a cell that are necessary to make up an organism. They can change over time, but are recreated with their original structure, arrangement, and interactions at the beginning of each generation. “That aspect of heredity, that the arrangement of molecules is similar across generations, is deeply underappreciated, and it leads to all sorts of misunderstandings of how heredity works,” argues Jose.
Sensors are specific entities that interact and respond to other entities or their environment. They respond to certain properties (the third factor mentioned by Jose), such as the arrangement of a molecule, its concentration in the cell, or its proximity to another substance.
Together, entities, sensors and properties allow a living organism to “feel” or “know” things about itself and its environment. In this way, part of that knowledge is used together with the genome to build an organism.
“This framework is built on years of experimental research in many labs, including ours, on epigenetics and multi-generational gene silencing combined with our growing interest in theoretical biology,” says Jose. “Given how two people who contract the same disease do not necessarily show the same symptoms, we really need to understand all the places where two people can be different—not just their genomes.”
In evolution, Jose’s structure suggests that organisms could develop through changes in the arrangement of molecules and without changes in the DNA sequence, and these factors need to be studied. In conservation science, the study suggests that attempts to preserve endangered species only through DNA banks are losing critical information stored in molecules that are not present in the genetic material.
Jose recognizes that there will be a lot of debate about these ideas and more studies are needed to prove them, yet the feedback from the scientific community has been positive so far. “Antony Jose’s generalization 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,” said Michael Levin, a biologist at the University Tufts, in a statement.