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Heterotachy
Heterotachy refers to variations in lineage-specific evolutionary rates over time. In the field of molecular evolution, the principle of heterotachy states that the substitution rate of sites in a gene can change through time. It has been proposed that the positions that show switches in substitution rate over time (that is, heterotachous sites) are good indicators of functional divergence. However, it appears that heterotachy is a much more general process, since most variable sites of homologous proteins with no evidence of functional shift are heterotachous. The covarion hypothesis is a specific form of heterotachy. Some studies have proposed functional divergence models that are also heterotachous. Additionally, some mixture models that do not explicitly account for rate-shift, but site-partitions evolving at different relative substitution rates across lineages are mathematically heterotachous. Failure to take heterotachy into account in phylogenetic reconstructions may lead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Evolution
Molecular evolution describes how Heredity, inherited DNA and/or RNA change over evolutionary time, and the consequences of this for proteins and other components of Cell (biology), cells and organisms. Molecular evolution is the basis of phylogenetics, phylogenetic approaches to describing the Tree of life (biology), tree of life. Molecular evolution overlaps with population genetics, especially on shorter timescales. Topics in molecular evolution include the origins of new genes, the genetic nature of complex traits, the genetic basis of adaptation and speciation, the Evolutionary developmental biology, evolution of development, and patterns and processes underlying genome, genomic changes during evolution. History The history of molecular evolution starts in the early 20th century with comparative biochemistry, and the use of "fingerprinting" methods such as immune assays, gel electrophoresis, and paper chromatography in the 1950s to explore homologous proteins. The advent of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covarion
{, class="wikitable" align="right" , - ! ! colspan=4 , Rate = 1 ! colspan=4 , Rate = 0 , - , , A1 , G1 , C1 , T1 , A0 , G0 , C0 , T0 , - , A1 , – , α , β , γ , δ , 0 , 0 , 0 , - , G1 , α , – , γ , β , 0 , δ , 0 , 0 , - , C1 , β , γ , – , α , 0 , 0 , δ , 0 , - , T1 , γ , β , α , – , 0 , 0 , 0 , δ , - , A0 , κδ , 0 , 0 , 0 , – , 0 , 0 , 0 , - , G0 , 0 , κδ , 0 , 0 , 0 , – , 0 , 0 , - , C0 , 0 , 0 , κδ , 0 , 0 , 0 , – , 0 , - , T0 , 0 , 0 , 0 , κδ , 0 , 0 , 0 , – , - The method of covarions, or ''co''ncomitantly ''vari''able cod''ons'', is a technique in computational phylogenetics that allows the hypothesized rate of molecular evolution at individual codons in a set of nucleotide sequences to vary in an autocorrelated manner. Under the covarion model, the rates of evolution on different branches of a hypothesized phylogenetic tree vary in an auto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mixture Models
In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proportion. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions or colloids. Mixtures are one product of mechanically blending or mixing chemical substances such as elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup. Despite the fact that there are no chemical changes to its constituents, the physical properties of a mixture, such as its melting point, may differ from those of the components. Some mixtures can be separated into their components by using physical (mechanical or thermal) means. Azeotropes are one kind of mixture that usually po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lineage (evolution)
An evolutionary lineage is a temporal series of populations, organisms, cells, or genes connected by a continuous line of descent from ancestor to descendant. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics. Phylogenetic representation of lineages upright=1.4, A rooted tree of life into three ancient monophyletic lineages: archaea.html" ;"title="bacteria, archaea">bacteria, archaea, and eukaryotes based on rRNA genes Lineages are typically visualized as subsets of a phylogenetic tree. A lineage is a single line of descent or linear chain within the tree, while a clade is a (usually branched) monophyletic group, containing a single ancestor and all its descendants. Phylogenetic trees are typically created from DNA, RNA or protein sequence data. Apart from this, morphological differences and similarities have been, and still are used to create phylogenetic trees. Sequences from different individua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetic Tree
A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. In evolutionary biology, all life on Earth is theoretically part of a single phylogenetic tree, indicating common ancestry. Phylogenetics is the study of phylogenetic trees. The main challenge is to find a phylogenetic tree representing optimal evolutionary ancestry between a set of species or taxa. Computational phylogenetics (also phylogeny inference) focuses on the algorithms involved in finding optimal phylogenetic tree in the phylogenetic landscape. Phylogenetic trees may be rooted or unrooted. In a ''rooted'' p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnetophyte
Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three relict genera: ''Gnetum'' (family Gnetaceae), ''Welwitschia'' (family Welwitschiaceae), and '' Ephedra'' (family Ephedraceae). The earliest unambiguous records of the group date to the Jurassic, and they achieved their highest diversity during the Early Cretaceous. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of small tubes (xylem) that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question, with many recent phylogenies finding them to be nested within the conifers. Though it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
