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Q-system (genetics)
Q-system is a genetic tool that allows to express transgenes in a living organism. Originally the Q-system was developed for use in the vinegar fly ''Drosophila melanogaster'', and was rapidly adapted for use in cultured mammalian cells, zebrafish, worms and mosquitoes. The Q-system utilizes genes from the ''qa'' cluster of the bread fungus ''Neurospora crassa'', and consists of four components: the transcriptional activator (QF/QF2/QF2w), the enhancer QUAS, the repressor QS, and the chemical de-repressor quinic acid. Similarly to GAL4/UAS and LexA/LexAop, the Q-system is a binary expression system that allows to express reporters or effectors (e.g. fluorescent proteins, ion channels, toxins and other genes) in a defined subpopulation of cells with the purpose of visualising these cells or altering their function. In addition, GAL4/UAS, LexA/LexAop and the Q-system function independently of each other and can be used simultaneously to achieve a desired pattern of reporter express ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar working in the 19th century in Brno, was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene. Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded to study the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance), and within the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Repressor
In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein. This blocking or reducing of expression is called repression. Function If an inducer, a molecule that initiates the gene expression, is present, then it can interact with the repressor protein and detach it from the operator. RNA polymerase then can transcribe the message (expressing the gene). A co-repressor is a molecule that can bind to the repressor and make it bind to the operator tightly, which decreases transcription. A repressor that binds with a co-repressor is termed an ''aporepressor'' or ''inactive repressor''. One type of aporepressor is the trp repre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and 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 noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Q-system Shematic
Q-systems are a method of directed graph transformations according to given grammar rules, developed at the Université de Montréal by Alain Colmerauer in 1967–70 for use in natural language processing. The Université de Montréal's machine translation system, TAUM-73, used the Q-Systems as its language formalism. The data structure manipulated by a Q-system is a Q-graph, which is a directed acyclic graph with one entry node and one exit node, where each arc bears a labelled ordered tree. An input sentence is usually represented by a linear Q-graph where each arc bears a word (tree reduced to one node labelled by this word). After analysis, the Q-graph is usually a bundle of 1-arc paths, each arc bearing a possible analysis tree. After generation, the goal is usually to produce as many paths as desired outputs, with again one word per arc. A Q-System consists of a sequence of Q-treatments, each being a set of Q-rules, of the form ">condition> The Q-treatments are app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell (biology)
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites.Cell Movements and the Shaping of the Vertebrate Body in Chapter 21 of Molecular Biology of the Cell '' fourth edition, edited by Bruce Alberts (2002) published by Garland Science. The Alberts text discusses how the "cellular building blocks" move to shape developing s. It is also common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxins
A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849–1919) and is derived from the word toxic. Toxins can be small molecules, peptides, or proteins that are capable of causing disease on contact with or absorption by body tissues interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their toxicity, ranging from usually minor (such as a bee sting) to potentially fatal even at extremely low doses (such as botulinum toxin). Toxins are largely secondary metabolites, which are organic compounds that are not directly involved in an organism's growth, development, or reproduction, instead often aiding it in matters of defense. Terminology Toxins are often distinguished from other chemical agents strictly based on their biological origin. Les ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ion Channels
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane, controlling the flow of ions across secretory and epithelial cells, and regulating cell volume. Ion channels are present in the membranes of all cells. Ion channels are one of the two classes of ionophoric proteins, the other being ion transporters. The study of ion channels often involves biophysics, electrophysiology, and pharmacology, while using techniques including voltage clamp, patch clamp, immunohistochemistry, X-ray crystallography, fluoroscopy, and RT-PCR. Their classification as molecules is referred to as channelomics. Basic features There are two distinctive features of ion channels that differentiate them from other types of ion transporter proteins: #The rate of ion transport through ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Fluorescent Protein
The green fluorescent protein (GFP) is a protein that exhibits bright green fluorescence when exposed to light in the blue to ultraviolet range. The label ''GFP'' traditionally refers to the protein first isolated from the jellyfish '' Aequorea victoria'' and is sometimes called ''avGFP''. However, GFPs have been found in other organisms including corals, sea anemones, zoanithids, copepods and lancelets. The GFP from ''A. victoria'' has a major excitation peak at a wavelength of 395 nm and a minor one at 475 nm. Its emission peak is at 509 nm, which is in the lower green portion of the visible spectrum. The fluorescence quantum yield (QY) of GFP is 0.79. The GFP from the sea pansy (''Renilla reniformis'') has a single major excitation peak at 498 nm. GFP makes for an excellent tool in many forms of biology due to its ability to form an internal chromophore without requiring any accessory cofactors, gene products, or enzymes / substrates other tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reporter Gene
In molecular biology, a reporter gene (often simply reporter) is a gene that researchers attach to a regulatory sequence of another gene of interest in bacteria, cell culture, animals or plants. Such genes are called reporters because the characteristics they confer on organisms expressing them are easily identified and measured, or because they are selectable markers. Reporter genes are often used as an indication of whether a certain gene has been taken up by or expressed in the cell or organism population. Common reporter genes To introduce a reporter gene into an organism, scientists place the reporter gene and the gene of interest in the same DNA construct to be inserted into the cell or organism. For bacteria or prokaryotic cells in culture, this is usually in the form of a circular DNA molecule called a plasmid. For viruses, this is known as a viral vector. It is important to use a reporter gene that is not natively expressed in the cell or organism under study, since ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GAL4/UAS System
The GAL4-UAS system is a biochemical method used to study gene expression and function in organisms such as the fruit fly. It is based on the finding by Hitoshi Kakidani and Mark Ptashne, and Nicholas Webster and Pierre Chambon in 1988 that Gal4 binding to UAS sequences activates gene expression. The method was introduced into flies by Andrea Brand and Norbert Perrimon in 1993 and is considered a powerful technique for studying the expression of genes. The system has two parts: the Gal4 gene, encoding the yeast transcription activator protein Gal4, and the UAS ( Upstream Activation Sequence), an enhancer to which GAL4 specifically binds to activate gene transcription. Overview The Gal4 system allows separation of the problems of defining which cells express a gene or protein and what the experimenter wants to do with this knowledge. Geneticists have created genetic variants of model organisms (typically fruit flies), called ''GAL4 lines'', each of which expresses GAL4 in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinic Acid
Quinic acid is a cyclitol, a cyclic polyol, and a cyclohexanecarboxylic acid. It is a colorless solid that can be extracted from plant sources. Quinic acid is implicated in the perceived acidity of coffee. Occurrence and preparation The compound is obtained from cinchona bark, coffee beans, and the bark of '' Eucalyptus globulus''. It is a constituent of the tara tannins. '' Urtica dioica'' is another common source. It is made synthetically by hydrolysis of chlorogenic acid. Quinic acid is also implicated in the perceived acidity of coffee. History and biosynthesis This substance was isolated for the first time in 1790 by German pharmacist Friedrich Christian Hofmann in Leer from Cinchona. Its transformation into hippuric acid by animal metabolism was studied by German chemist Eduard Lautemann in 1863.Lautemann, E. (1863"Ueber die Reduction der Chinasäure zu Benzoësäure und die Verwandlung derselben in Hippursäure im thierischen Organismus"(On the reduction of quini ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
