Selective intra-dinucleotide interactions and periodicities of bases separated by K sites: a new vision and tool for phylogeny analyses

Direct tests of the random or non-random distribution of nucleotides on genomes have been devised to test the hypothesis of neutral, nearly-neutral or selective evolution. These tests are based on the direct base distribution and are independent of the functional (coding or non-coding) or structural (repeated or unique sequences) properties of the DNA. The first approach described the longitudinal distribution of bases in tandem repeats under the Bose-Einstein statistics. A huge deviation from randomness was found. A second approach was the study of the base distribution within dinucleotides whose bases were separated by 0, 1, 2... K nucleotides. Again an enormous difference from the random distribution was found with significances out of tables and programs. These test values were periodical and included the 16 dinucleotides. For example a high ¨positive¨ (more observed than expected dinucleotides) value, found in dinucleotides whose bases were separated by (3K + 2) sites, was preceded by two smaller ¨negative¨ (less observed than expected dinucleotides) values, whose bases were separated by (3K) or (3K + 1) sites. We examined mtDNAs, prokaryote genomes and some eukaryote chromosomes and found that the significant non-random interactions and periodicities were present up to 1000 or more sites of base separation and in human chromosome 21 until separations of more than 10 millions sites. Each nucleotide has its own significant value of its distance to neutrality; this yields 16 hierarchical significances. A three dimensional table with the number of sites of separation between the bases and the 16 significances (the third dimension is the dinucleotide, individual or taxon involved) gives directly an evolutionary state of the analyzed genome that can be used to obtain phylogenies. An example is provided.

Em cada lugar um brincar: reflexão evolucionista sobre universalidade e diversidade / Play activity for all places: thinking about the universality and the diversity from an evolutionary perspective

Pensar sobre a brincadeira infantil como adaptação necessária para a vida, indica um paralelo entre universalidade e diversidade deste fenômeno. Apresentamos aqui evidências apontadas por pesquisas mostrando particularidades observadas nas brincadeiras em contextos específicos. E perguntamos como variações no brincar, relacionadas aos contextos particulares, associam-se ás suas funções no desenvolvimento ontogenético. Nossa reflexão é traçada a partir de uma abordagem evolucionista, relacionando características intrínsecas das brincadeiras com possíveis funções e adaptações filogenéticas e ontogenéticas, na espécie humana. Os resultados descritos nas pesquisas observadas nos indicam evidências do brincar como comportamento funcional e adaptativo para o próprio período da infância, onde as crianças provam seu ambiente e podem aprender e praticar comportamentos adaptáveis a cada ambiente em especial. Além disso, dado o papel fundamental do contexto e cultura na brincadeira, percebemos a possibilidade de investigar como a diversidade do desenvolvimento humano se relaciona com os aspectos universais dos indivíduos.

Thinking about children's play as a necessary adaptation for human existence, leads us to think about what is universal and what is different about this phenomenon. We present here evidence quoted in various elements of research that provide detail in specific contexts, and we discuss how variation in play is related to functions in ontogenetic development. We follow the evolutionary theories, relating intrinsic characteristics of play to possible functions and phylogenetic and ontogenetic adaptations in the human species. The research examined indicates evidence of play as a functional and adaptive behavior for childhood, where children test their environment and can learn and practice adaptable behavior specific to each environment. Moreover, given the fundamental role of the context and culture in play, we can see that the possibility exists of investigating how the diversity of human development can be linked to the universal aspects of individual development.