Network properties of genotype-phenotype mappings

One fundamental question in biology is which are the processes that give rise to a differentiation between individuals, species and groups. Since the discovery of genes as the units of heredity, there has been a tendency to view genes as the determinants of the physical characteristics. It was W.Johannsen [1] who first proposed the distinction between genotype and phenotype by studying the heritable variation in plants. The hereditary dispositions of organisms was differentiated from the ways in which those dispositions have physical manifes- tation. The genotype-phenotype distinction was a conceptual framework from which studies of development, genetics and evolution achieved a new perspec- tive, being the next step the understanding of how is the mapping between these two differenciate spaces.The first section of this work contains a literature review of the main con- cepts that have been developed in time with the study of the genome and its expression and from which the genotype-phenotype mapping is considered nowa- days as a crucial framework wich picks up the complex mechanism by which individuals are developed [1-14]. It is also shown in the last part of this sec- tion actual genotype-phenotype mappings which resulting properties are going to be analyzed and compared in the third section [18,19][21-23]. The second section shows a literature review of the concept of neutral evolution, which ex- plains the invariance of phenotype behind multiple point mutations, and how from this mechanism which is observed in actual organisms along evolution is possible the punctuacted equilibria phenomenon. Behind this concept of evo- lution scientific community is constructing neutral networks, which are defined from the genotype-phenotype mappings, and studying some properties of these networks having a biological interpretation [15-17]. This section also shows dif- ferent constructions of neutral networks arising from genotype-phenotype map- pings defined in the first section. Note that most of the models analyzed are based on RNA folding. The third section shows network properties of genotype- phenotype mappings of the different models which are defined in the lastest sec- tions and are compared to each other. The fourth section explains a new model based on a cellular automata. This model is thougth to be appropiate because of its originality and mathematical nature. Some measures that have been used in previous models are applied over the new model in order to compare the resulting biological properties. For finalyzing the work, a new measure is de- veloped and applied to the model to obtain interesting biological interpretations.The main goal of this work is to compare different models of neutral net- works to a new one based on a cellular automaton. From this comparison, we can elucidate that from a very simple and abstract model it is possible to ob- tain similar results to very much complicated models based on RNA folding or protein function. As a second goal, biological properties such as robust- ness, evolvability and accesibility are studied to get an intuitive idea about how evolution operates behind neutral mutations.Peer reviewe