jueves, 5 de marzo de 2009

Selección del Complexity Digest - Marzo

Wings, Horns, and Butterfly Eyespots: How Do Complex Traits Evolve?, PLoS Biol

Excerpt: Throughout their evolutionary history, organisms have evolved numerous complex morphological, physiological, and behavioral adaptations to increase their chances of survival and reproduction. (...) The way that most of these and other adaptations first evolved, however, is still largely unknown. In the last two decades we have learned that novel traits appear to be built using old genes wired in novel ways [5], but it is still a mystery whether these novel traits evolve when genes are rewired de novo, one at a time, into new developmental networks, or whether clusters of pre-wired genes are co-opted into the development of the new trait. The speed of evolution of novel complex traits is likely to depend greatly on which of these two mechanisms underlies their origin. It is important, thus, to understand how novel complex traits evolve.

Neutrality and Robustness in Evo-devo: Emergence of Lateral Inhibition, SFI Working Papers

Abstract: Embryonic development is defined by the hierarchical dynamical process that translates genetic information (genotype) into a spatial gene expression pattern (phenotype) providing the positional information for the correct unfolding of the organism. The nature and evolutionary implications of genotype-phenotype mapping still remain key topics in evolutionary developmental biology (evo-devo). We have explored here issues of neutrality, robustness and diversity in evo-devo by means of a simple model of gene regulatory networks. The small size of the system allowed an exhaustive analysis of the entire fitness landscape and the extent of its neutrality. This analysis shows that evolution leads to a class of robust genetic networks with an expression pattern characteristic of lateral inhibition. This class is a repertoire of distinct implementations of this key developmental process, the diversity of whom provides valuable clues about its underlying causal principles.

Mutation Patterns in the Human Genome: More Variable Than Expected, PLoS Biol

Excerpt: The development, survival, and reproduction of an organism depend on the genetic information that is carried in its genome, yet the transmission of genetic information is not perfectly accurate: new mutations occur at each generation. These mutations are the primary cause of the genetic diversity on which natural selection can operate, and hence are the sine qua non of evolution. A better knowledge of mutation processes is crucial for investigating the causes of genetic diseases or cancer and for understanding evolutionary processes.

Physics of Evolution: Selection without Fitness, SFI Working Papers

Excerpt: Traditionally evolution is seen as a process where from a pool of possible variations of a population (e.g. biological species or industrial goods) a few variations get selected which survive and proliferate, whereas the others vanish. Survival probability is typically associated with the fitness of a particular variation. In this paper we argue that the notion of fitness is an a posteriori concept, in the sense that one can assign higher fitness to species that survive but one can generally not derive or even measure fitness or fitness landscapes per se. For this reason we think that in a physical theory of evolution such notions should be avoided. In this spirit, here we propose a random matrix model of evolution where selection mechanisms are encoded in the interaction matrices of species. We are able to recover some key facts of evolution dynamics (...)

Attractors and Democratic Dynamics, Science

Excerpt: Consider two concepts of transcriptional regulation. In a "molecular autocracy," master genes respond to environmental or developmental stimuli by regulating thousands of genes, either directly or through other transcription factors. In a "molecular democracy," all genes exert a regulatory influence on all other genes, and phenotypic change (altered cell behavior) is brought about through the concerted action of thousands of genes. These scenarios are extreme and cells operate under a condition that is somewhere intermediate (see the figure) (1). But the choice of concept affects how regulation is studied.

  • Source: Attractors and Democratic Dynamics, Yaneer Bar-Yam, Dion Harmon, Benjamin de Bivort, DOI: 10.1126/science.1163225, Science Vol. 323. no. 5917, pp. 1016 - 1017, 2009/02/20

No hay comentarios: