lunes, 8 de noviembre de 2010

Selección de "Noticias Complejas"

What Is Epigenetics?, Science

Excerpt: The cells in a multicellular organism have nominally identical DNA sequences (and therefore the same genetic instruction sets), yet maintain different terminal phenotypes. This nongenetic cellular memory, which records developmental and environmental cues (and alternative cell states in unicellular organisms), is the basis of epi-(above)"genetics.

Is Life Impossible? Information, Sex, and the Origin of Complex Organisms, Evolution

Excerpt: The earliest organisms are thought to have had high mutation rates. It has been asserted that these high mutation rates would have severely limited the information content of early genomes. This has led to a well-known “paradox” because, in contemporary organisms, the mechanisms that suppress mutations are quite complex and a substantial amount of information is required to construct these mechanisms. The paradox arises because it is not clear how efficient error-suppressing mechanisms could have evolved, and thus allowed the evolution of complex organisms, at a time when mutation rates were too high to permit the maintenance of very substantial amounts of information within genomes. Here, we use concepts from the formal theory of information to calculate the amount of genomic information that can be maintained. (...)

A map of human genome variation from population-scale sequencing, Nature

Excerpt: The 1000 Genomes Project aims to provide a deep characterization of human genome sequence variation as a foundation for investigating the relationship between genotype and phenotype. Here we present results of the pilot phase of the project, designed to develop and compare different strategies for genome-wide sequencing with high-throughput platforms.

Diversity of Human Copy Number Variation and Multicopy Genes, Science

Excerpt: Copy number variants affect both disease and normal phenotypic variation, but those lying within heavily duplicated, highly identical sequence have been difficult to assay. By analyzing short-read mapping depth for 159 human genomes, we demonstrated accurate estimation of absolute copy number for duplications as small as 1.9 kilobase pairs, ranging from 0 to 48 copies. (...) These data identify human-specific expansions in genes associated with brain development, reveal extensive population genetic diversity, and detect signatures consistent with gene conversion in the human species. Our approach makes ~1000 genes accessible to genetic studies of disease association.

Genome size, self-organization and DNA's dark matter, Complexity

Abstract: Chromosomes exhibit several features indicating that its spatiotemporal dynamics is self-organized. It has been recently suggested that a negative correlation between genome size and mean chromosome number would also be a fingerprint of selforganization, related to how human language is organized at the level of words and syllables. However, the vast dominance of non-coding DNA in eukaryotic genomes should prevent an interpretation of genome/chromosome size based on functional trade-offs related to information storage and transmission. Moreover, the reported negative correlation is shown to be an inevitable consequence of the definitions of chromosome and genome length and it is thus unrelated to any type of special generative process.

The Origins Of Modern Biodiversity On Land, Phil. Trans. B

Excerpt: Comparative studies of large phylogenies of living and extinct groups have shown that most biodiversity arises from a small number of highly species-rich clades. To understand biodiversity, it is important to examine the history of these clades on geological time scales. This is part of a distinct phylogenetic expansion view of macroevolution, and contrasts with the alternative, non-phylogenetic equilibrium approach to the history of biodiversity. The latter viewpoint focuses on density-dependent models in which all life is described by a single global-scale model, and a case is made here that this approach may be less successful at representing the shape of the evolution of life.

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