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DNA Base Flipping
DNA base flipping, or nucleotide flipping, is a mechanism in which a single nucleotide base, or nucleobase, is rotated outside the nucleic acid double helix. This occurs when a nucleic acid-processing enzyme needs access to the base to perform work on it, such as its excision for replacement with another base during DNA repair. It was first observed in 1994 using X-ray crystallography in a methyltransferase enzyme catalyzing methylation of a cytosine base in DNA. Since then, it has been shown to be used by different enzymes in many biological processes such as DNA methylation, various DNA repair mechanisms, and DNA replication. It can also occur in RNA double helices or in the DNA:RNA intermediates formed during RNA transcription. DNA base flipping occurs by breaking the hydrogen bonds between the bases and unstacking the base from its neighbors. This could occur through an active process, where an enzyme binds to the DNA and then facilitates rotation of the base, or a passiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicases
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands (hence '' helic- + -ase''), using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases. The human genome codes for 95 non-redundant helicases: 64 RNA helicases and 31 DNA helicases. Many cellular processes, such as DNA replication, transcription, translation, recombination, DNA repair, and ribosome biogenesis involve the separation of nucleic acid strands that necessitates the use of helicases. Some specialized helicases are also involved in sensing of viral nucleic acids during infection and fulfill a immunological function. Function Helicases ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral replication, mitosis, or meiosis or other types of DNA repair#DNA damage, damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication (DNA repair#Translesion synthesis, translesion synthesis). Mutations may also result from Insertion (genetics), insertion or Deletion (genetics), deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics (phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uracil Base Glycosidase
Uracil () (symbol U or Ura) is one of the four nucleobases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine. Uracil is a common and naturally occurring pyrimidine derivative. The name "uracil" was coined in 1885 by the German chemist Robert Behrend, who was attempting to synthesize derivatives of uric acid. Originally discovered in 1900 by Alberto Ascoli, it was isolated by hydrolysis of yeast nuclein; it was also found in bovine thymus and spleen, herring sperm, and wheat germ. It is a planar, unsaturated compound that has the ability to absorb light. Based on 12C/13C isotopic ratios of organic compounds found in the Murchison meteorite, it is believed that uracil, xanthine, and related molecules can also be formed extraterrestrially. Data from the Cassini mission, orbiting in the Sat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transposase
A transposase is any of a class of enzymes capable of binding to the end of a transposon and catalysing its movement to another part of a genome, typically by a cut-and-paste mechanism or a replicative mechanism, in a process known as transposition. The word "transposase" was first coined by the individuals who cloned the enzyme required for transposition of the Tn3 transposon. The existence of transposons was postulated in the late 1940s by Barbara McClintock, who was studying the inheritance of maize, but the actual molecular basis for transposition was described by later groups. McClintock discovered that some segments of chromosomes changed their position, jumping between different loci or from one chromosome to another. The repositioning of these transposons (which coded for color) allowed other genes for pigment to be expressed. Transposition in maize causes changes in color; however, in other organisms, such as bacteria, it can cause antibiotic resistance. Transposition is al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tn10
Tn''10'' is a transposable element, which is a sequence of DNA that is capable of mediating its own movement from one position in the DNA of the host organism to another. There are a number of different transposition mechanisms in nature, but Tn''10'' uses the non-replicative cut-and-paste mechanism. The transposase protein recognizes the ends of the element and cuts it from the original locus. The protein-DNA complex then diffuses away from the donor site until random collisions brings it in contact with a new target site, where it is integrated. To accomplish this reaction the 50 kDa transposase protein must break four DNA strands to free the transposon from the donor site, and perform two strand exchange reactions to integrate the element at the target site. This leaves two strands unjoined at the target site, but the host DNA repair proteins take care of this. The target site selection is essentially random, but there is a preference for the sequence 5'-GCTNAGC-3'. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uracil-DNA Glycosylase
Uracil-DNA glycosylase is also known as UNG or UDG. Its most important function is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosidic bond and initiating the base-excision repair (BER) pathway. Function The human gene encodes one of several uracil-DNA glycosylases. Alternative promoter usage and splicing of this gene leads to two different isoforms: the mitochondrial UNG1 and the nuclear UNG2. One important function of uracil-DNA glycosylases is to prevent mutagenesis by eliminating uracil from DNA molecules by cleaving the N-glycosidic bond and initiating the base-excision repair (BER) pathway. Uracil bases occur from cytosine deamination or misincorporation of dUMP residues. After a mutation occurs, the mutagenic threat of uracil propagates through any subsequent DNA replication steps. Once unzipped, mismatched guanine and uracil pairs are separated, and DNA polymerase inserts complementary bases to form a guanine-cytosine (GC) pair in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Conformation
Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers specifically polypeptides formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may also be called a ''residue'' indicating a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond. By convention, a chain under 30 amino acids is often identified as a peptide, rather than a protein. To be able to perform their biological function, proteins fold into one or more specific spatial conformations driven by a number of non-covalent interactions such as hydrogen bonding, ionic interactions, Van der Waals forces, and hydrophobic packing. To understand the functions of proteins at a molecular level, it is often necessary to determine their three-dimensional structure. This i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gibbs Free Energy
In thermodynamics, the Gibbs free energy (or Gibbs energy; symbol G) is a thermodynamic potential that can be used to calculate the maximum amount of work that may be performed by a thermodynamically closed system at constant temperature and pressure. It also provides a necessary condition for processes such as chemical reactions that may occur under these conditions. The Gibbs free energy change , measured in joules in SI) is the ''maximum'' amount of non-expansion work that can be extracted from a closed system (one that can exchange heat and work with its surroundings, but not matter) at fixed temperature and pressure. This maximum can be attained only in a completely reversible process. When a system transforms reversibly from an initial state to a final state under these conditions, the decrease in Gibbs free energy equals the work done by the system to its surroundings, minus the work of the pressure forces. The Gibbs energy is the thermodynamic potential that is m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Major Groove
Major (commandant in certain jurisdictions) is a military rank of commissioned officer status, with corresponding ranks existing in many military forces throughout the world. When used unhyphenated and in conjunction with no other indicators, major is one rank above captain, and one rank below lieutenant colonel. It is considered the most junior of the field officer ranks. Background Majors are typically assigned as specialised executive or operations officers for battalion-sized units of 300 to 1,200 soldiers while in some nations, like Germany, majors are often in command of a company. When used in hyphenated or combined fashion, the term can also imply seniority at other levels of rank, including ''general-major'' or ''major general'', denoting a low-level general officer, and ''sergeant major'', denoting the most senior non-commissioned officer (NCO) of a military unit. The term ''major'' can also be used with a hyphen to denote the leader of a military band such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double Helix
A double is a look-alike or doppelgänger; one person or being that resembles another. Double, The Double or Dubble may also refer to: Film and television * Double (filmmaking), someone who substitutes for the credited actor of a character * ''The Double'' (1934 film), a German crime comedy film * ''The Double'' (1971 film), an Italian film * ''The Double'' (2011 film), a spy thriller film * ''The Double'' (2013 film), a film based on the Dostoevsky novella * '' Kamen Rider Double'', a 2009–10 Japanese television series ** Kamen Rider Double (character), the protagonist in a Japanese television series of the same name Food and drink * Doppio, a double shot of espresso * Dubbel, a strong Belgian Trappist beer or, more generally, a strong brown ale * A drink order of two shots of hard liquor in one glass * A "double decker", a hamburger with two patties in a single bun Games * Double, action in games whereby a competitor raises the stakes ** , in contract bridge ** Doub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Model Of The EhMeth-DNA Complex
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure. Models can be divided into physical models (e.g. a model plane) and abstract models (e.g. mathematical expressions describing behavioural patterns). Abstract or conceptual models are central to philosophy of science, as almost every scientific theory effectively embeds some kind of model of the physical or human sphere. In commerce, "model" can refer to a specific design of a product as displayed in a catalogue or show room (e.g. Ford Model T), and by extension to the sold product itself. Types of models include: Physical model A physical model (most commonly referred to simply as a model but in this context distinguished from a conceptual model) is a smaller or larger physical copy of an object. The object being modelled may be small ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
