PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Biological Evolution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed1986

Protein structure and neutral theory of evolution.

The neutral theory of evolution is extended to the origin of protein molecules. Arguments are presented which suggest that the amino acid sequences of many globular proteins mainly represent "memorized" random sequences while biological evolution reduces to the "editing" these random sequences. Physical requirements for a functional globular protein are formulated and it is shown that many of these requirement do not involve strategical selection of amino acid sequences during biological evolution but are inherent also for typical random sequences. In particular, it is shown that random sequences of polar and amino acid residues can form alpha-helices and beta-strand with lengths and arrangement along the chain similar to those in real globular proteins. These alpha- and beta-regions in random sequences can form three-dimensional folding patterns also similar to those in proteins. The arguments are presented suggesting that even the tight packing of side groups inside protein core do not require very strong biological selection of amino acid sequences either. Thus many structural features of real proteins can exist also in random sequences and the biological selection is needed mainly for the creation of active site of protein and for their stability under physiological conditions.

Amino Acid Sequence↗
PubMed2002

Computational and evolutionary aspects of language.

Language is our legacy. It is the main evolutionary contribution of humans, and perhaps the most interesting trait that has emerged in the past 500 million years. Understanding how darwinian evolution gives rise to human language requires the integration of formal language theory, learning theory and evolutionary dynamics. Formal language theory provides a mathematical description of language and grammar. Learning theory formalizes the task of language acquisition it can be shown that no procedure can learn an unrestricted set of languages. Universal grammar specifies the restricted set of languages learnable by the human brain. Evolutionary dynamics can be formulated to describe the cultural evolution of language and the biological evolution of universal grammar.

Biological Evolution↗
PubMed1998

The forces driving molecular evolution.

Competitive replication among RNA or DNA molecules at linear and non-linear rates of propagation has been reviewed from the perspective of a recent physicochemical model of molecular evolution and the findings are applied to pre-replication, prebiotic and biological evolution. A system of competitively replicating molecules was seen to follow a path of least action on both its thermodynamic and kinetic branch, in evolving toward steady state kinetics and equilibrium for the nucleotide condensation reaction. Stable and unstable states of coexistence, between competing molecular species, arise at nonlinear rates of propagation, and they derive from an equilibrium between kinetic forces. The de novo formation of self-replicating RNA molecules involves damping of these scalar forces, error tolerance and RNA driven strand separation. Increases in sequence complexity in the transition to self-replication does not exceed the free energy dissipated in RNA synthesis. Retrodiction of metabolic pathways and phylogenetic evidence point to the occurrence of three pre-replication metabolic systems, driven by autocatalytic C-fixation cycles. Thermodynamic and kinetic factors led to the replication take over. Biological evolution was found to involve resource capture, in addition to competition for a shared resource.

Archaea↗
PubMedDate not supplied

[Protein as an edited random copolymer].

It is widely believed that the unique primary structure of a given protein is quite necessary for its folding into a certain three-dimensional structure as well as for its functioning and is a result of a directed selection in the course of biological evolution. The present paper provides arguments in favour of an alternative point of view according to which typical three-dimensional structures of globular proteins are characteristic even for random sequences of amino acid residues. Therefore it may be possible that primary structures of proteins are mainly examples of random amino acid sequences slightly edited in the course of biological evolution to impart them some additional (functional) meaning.

Amino Acid Sequence↗
PubMed1997

Developmental phenotypic plasticity: where ecology and evolution meet molecular biology.

The plastic response of phenotypic traits to environmental change is a common research focus in several disciplines-from ecology and evolutionary biology to physiology and molecular genetics. The use of model systems such as the flowering plant Arabidopsis thaliana has facilitated a dialogue between developmental biologists asking how plasticity is controlled (proximate causes) and organismal biologists asking why plasticity exists (ultimate causes). Researchers studying ultimate causes and consequences are increasingly compelled to reject simplistic, 'black box' models, while those studying proximate causes and mechanisms are increasingly obliged to subject their interpretations to ecological 'reality checks.' We review the successful multidisciplinary efforts to understand the phytochrome-mediated shade-avoidance and light-seeking responses of flowering plants as a pertinent example of convergence between evolutionary and molecular biology. In this example, the two-way exchange between reductionist and holist camps has been essential to rapid and sustained progress. This should serve as a model for future collaborative efforts towards understanding the responses of organisms to their constantly changing environments.

Arabidopsis↗
PubMedDate not supplied

Confirmation of primary active substances from high throughput screening of chemical and biological populations: a statistical approach and practical considerations.

Many biologically important substances are discovered through screening of relevant chemical or biological libraries. The ability to find the active substances ("hits") from any random collection is largely determined by the quality of the assay and screening conditions. When a large population is screened for a specific characteristic, each member of that population is usually tested only once. Errors in the measurements require additional follow-up tests to confirm that each hit from the primary screen is truly active. In this report, we present a statistical model system that predicts the reliability of hits from a primary test as affected by the error in the assay and the choice of the hit threshold (hit limit). The hit confirmation rate, as well as false positive (representing substances that initially fall above the hit limit but whose true activity are below the hit limit) and false negative (representing substances that initially fall below the hit limit but whose true activity are in fact greater than the hit limit) rates have been analyzed with this model by computational simulation. This model can also be used in screen validation and post-screening data analysis. The statistical analysis presented here has broad implications and is applicable to screening of any large population for any specific characteristic. Obvious applications include drug discovery, gene chip analysis, population biology, directed molecular evolution, biological panning, and combinatorial material sciences.

Biological Factors↗