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G-value Paradox
The G-value paradox arises from the lack of correlation between the number of protein-coding genes among eukaryotes and their relative biological complexity. The microscopic nematode ''Caenorhabditis elegans'', for example, is composed of only a thousand cells but has about the same number of genes as a human. Researchers suggest resolution of the paradox may lie in mechanisms such as alternative splicing and complex gene regulation that make the genes of humans and other complex eukaryotes relatively more productive. DNA and biological complexity The lack of correlation between the morphological complexity of eukaryotes and the amount of genetic information they carry has long puzzled researchers. The sheer amount of DNA in an organism, measured by the mass of DNA present in the nucleus or the number of constituent nucleotide pairs, varies by several orders of magnitude among eukaryotes and often is unrelated to an organism's size or developmental complexity. One amoeba has 200 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabolic reactions, DNA replication, Cell signaling, responding to stimuli, providing Cytoskeleton, structure to cells and Fibrous protein, organisms, and Intracellular transport, transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the Nucleic acid sequence, nucleotide sequence of their genes, and which usually results in protein folding into a specific Protein structure, 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called pep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (biology)
Transcription is the process of copying a segment of DNA into RNA for the purpose of gene expression. Some segments of DNA are transcribed into RNA molecules that can encode proteins, called messenger RNA (mRNA). Other segments of DNA are transcribed into RNA molecules called non-coding RNAs (ncRNAs). Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a Complementarity (molecular biology), complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, Antiparallel (biochemistry), antiparallel RNA strand called a primary transcript. In virology, the term transcription is used when referring to mRNA synthesis from a viral RNA molecule. The genome of many Orthornavirae, RNA viruses is composed of Sense (molecular biology), negative-sense RNA which acts as a template for positive sense viral messenger RNA - a necessary step in the synthesis of viral proteins needed for viral replication. This process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome of around 135 Base pair#Length measurements, megabase pairs. It was the first plant to have its genome sequenced, and is an important tool for understanding the molecular biology of many plant traits, including flower development and phototropism, light sensing. Description ''Arabidopsis thaliana'' is an annual plant, annual (rarely biennial plant, biennial) plant, usually growing to 20–25 cm tall. The leaf, leaves form a rosette at the base of the plant, with a few leaves also on the flowering Plant ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zebrafish
The zebrafish (''Danio rerio'') is a species of freshwater ray-finned fish belonging to the family Danionidae of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often called a " tropical fish" although it is both tropical and subtropical). The zebrafish is an important and widely used vertebrate model organism in scientific research, particularly developmental biology, but also gene function, oncology, teratology, and drug development, in particular pre-clinical development. It is also notable for its regenerative abilities, and has been modified by researchers to produce many transgenic strains. Taxonomy The zebrafish is a derived member of the genus '' Brachydanio'', of the family Cyprinidae. It has a sister-group relationship with '' Danio aesculapii''. Zebrafish are also closely related to the genus '' Devario'', as demonstrated by a phylogenetic tree of close species. Distri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drosophila Melanogaster
''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly", or "banana fly". In the wild, ''D. melanogaster'' are attracted to rotting fruit and fermenting beverages, and are often found in orchards, kitchens and pubs. Starting with Charles W. Woodworth's 1901 proposal of the use of this species as a model organism, ''D. melanogaster'' continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and Life history theory, life history evolution. ''D. melanogaster'' was the first animal to be Fruit flies in space, launched into space in 1947. As of 2017, six Nobel Prizes have been awarded to drosophilists for their work using the insect. ''Drosophila melanogaster'' is typically used in research owing to its rapid life cycle, relatively simple genetics with on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daphnia Pulex
''Daphnia pulex'' is the most common species of water flea. It has a cosmopolitan distribution: the species is found throughout the Americas, Europe, and Australia. It is a model species, and was the first crustacean to have its genome sequenced. Description ''D. pulex'' is an arthropod whose body segments are difficult to distinguish. It can only be recognised by its appendages (only ever one pair per segment), and by studying its internal anatomy. The head is distinct and is made up of six segments, which are fused together even as an embryo. It bears the arthropod mouthparts, mouthparts, and two pairs of antenna (biology), antennae, the second pair of which is enlarged into powerful organs used for swimming. No clear division is seen between the thorax and abdomen, which collectively bear five pairs of appendages. The shell surrounding the animal extends posteriorly into a Spine (zoology), spine. Like most other ''Daphnia'' species, ''D. pulex'' reproduces by cyclical parthenog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequencing
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succinctly summarizes much of the atomic-level structure of the sequenced molecule. DNA sequencing DNA sequencing is the process of determining the nucleotide order of a given DNA fragment. So far, most DNA sequencing has been performed using the chain termination method developed by Frederick Sanger. This technique uses sequence-specific termination of a DNA synthesis reaction using modified nucleotide substrates. However, new sequencing technologies such as pyrosequencing are gaining an increasing share of the sequencing market. More genome data are now being produced by pyrosequencing than Sanger DNA sequencing. Pyrosequencing has enabled rapid genome sequencing. Bacterial genomes can be sequenced in a single run with several times cov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Genome Project
The Human Genome Project (HGP) was an international scientific research project with the goal of determining the base pairs that make up human DNA, and of identifying, mapping and sequencing all of the genes of the human genome from both a physical and a functional standpoint. It started in 1990 and was completed in 2003. It was the world's largest collaborative biological project. Planning for the project began in 1984 by the US government, and it officially launched in 1990. It was declared complete on 14 April 2003, and included about 92% of the genome. Level "complete genome" was achieved in May 2021, with only 0.3% of the bases covered by potential issues. The final gapless assembly was finished in January 2022. Funding came from the US government through the National Institutes of Health (NIH) as well as numerous other groups from around the world. A parallel project was conducted outside the government by the Celera Corporation, or Celera Genomics, which was formall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genome
A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of junk DNA with no evident function. Almost all eukaryotes have mitochondrial DNA, mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplast DNA, chloroplasts with a chloroplast genome. The study of the genome is called genomics. The genomes of many organisms have been Whole-genome sequencing, sequenced and various regions have been annotated. The first genome to be sequenced was that of the virus φX174 in 1977; the first genome sequence of a prokaryote (''Haemophilus influenzae'') was published in 1995; the yeast (''Saccharomyces cerevisiae'') genome was the first eukaryotic genome to be sequenced in 1996. The Human Genome Project ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prokaryote
A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Greek (), meaning 'before', and (), meaning 'nut' or 'kernel'. In the earlier two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. However, in the three-domain system, based upon molecular phylogenetics, prokaryotes are divided into two domain (biology), domains: Bacteria and Archaea. A third domain, Eukaryote, Eukaryota, consists of organisms with nuclei. Prokaryotes evolution, evolved before eukaryotes, and lack nuclei, mitochondria, and most of the other distinct organelles that characterize the eukaryotic cell. Some unicellular prokaryotes, such as cyanobacteria, form colony (biology), colonies held together by biofilms, and large colonies can create multilayered microbial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Load
Genetic load is the difference between the fitness of an average genotype in a population and the fitness of some reference genotype, which may be either the best present in a population, or may be the theoretically optimal genotype. The average individual taken from a population with a low genetic load will generally, when grown in the same conditions, have more surviving offspring than the average individual from a population with a high genetic load. Genetic load can also be seen as reduced fitness at the population level compared to what the population would have if all individuals had the reference high-fitness genotype. High genetic load may put a population in danger of extinction. Fundamentals Consider n genotypes \mathbf _1, \dots, \mathbf _n, which have the fitnesses w_1, \dots, w_n and frequencies p_1, \dots, p_n, respectively. Ignoring frequency-dependent selection, the genetic load L may be calculated as: :L = where w_\max is either some theoretical optimum, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudogene
Pseudogenes are nonfunctional segments of DNA that resemble functional genes. Pseudogenes can be formed from both protein-coding genes and non-coding genes. In the case of protein-coding genes, most pseudogenes arise as superfluous copies of functional genes, either directly by gene duplication or indirectly by Reverse transcriptase, reverse transcription of an mRNA transcript. Pseudogenes are usually identified when genome sequence analysis finds gene-like sequences that lack regulatory sequences or are incapable of producing a functional product. Pseudogenes are a type of junk DNA. Most non-bacterial genomes contain many pseudogenes, often as many as functional genes. This is not surprising, since various biological processes are expected to accidentally create pseudogenes, and there are no specialized mechanisms to remove them from genomes. Eventually pseudogenes may be deleted from their genomes by chance of DNA replication or DNA repair errors, or they may accumulate so many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
